Hello Aircraft Designers & Friends!
Welcome to the AircraftDesign.Com Open Blog - all are welcome. Comments about the website are especially appreciated - what was useful, how are you using it, whatever. Open questions to Dan Raymer are fine too. You do not have to register or provide your name, but it would be nice. Keep it clean, and hey - this isn’t instant-messaging so spare us the IM slang! IMHO. J/K.
Archived postings and replies, organized by category, can be seen at http://www.aircraftdesign.com/aircraftdesignblog.html.
Please don’t post links to other websites here, or ask me to comment on them. If there is a website I should add to my links page, email it to me (but no purely commercial websites, airplanes for sale, politics, etc…).
January 22nd, 2009 at 10:10 am
Great website!! We are happy to see the Dynalifters in it, and the text book you wrote as well.
Dan has been a great asset to our critical design, and helped us determine if we should continue or stop. We are all thankful we continue for 9 years now. We have used his design through many meetings. Not one person argues the facts/physics Dan showed in his studies.
He’s a great guy to work with.
Blessings,
Bob Rist
Ohio Airships, Inc.
January 25th, 2009 at 10:18 am
>>> Dan Blogs Without a Question to Answer <<<
How about that water landing? Amazing! What a cool-headed pilot. Not much sense of humor though (or maybe his company’s lawyers had it surgically removed). The pilots I know would give a speach something like this:
“Thank you, thank you. I really don’t deserve the Keys to the City, but I’ll take them - hopefully they unlock the local bank… or a good bar. I don’t deserve all this attention - the water landing was actually my fault. I saw those geese and swerved right into them, hoping to spear dinner on my pitot static probe. Missed, dang it. About the river landing - hitting those geese made me lose my contact lenses - I thought it was LaGuardia Runway 31. And walking the aisle twice as the plane was sinking - looking for my contacts. Passengers - sorry about the bags, but luckily most of them didn’t get on the plane in the first place so you can have what’s left after the baggage handlers steal the good stuff. Thank you, and Live, From New York, its…….”
January 27th, 2009 at 7:42 am
Dear SIr,
sir, can you send me the steps and details for conceptual designing SST at undergraduate level? I awnt the latest 21th generation SST design sketches and also some concept would be use.. plz send me sir… i m waiting.
January 27th, 2009 at 8:06 am
Hello,
My textbook explains how to design airplanes. The same process applies to an SST. The first part of the job - your job - is coming up with some concept sketches. You should research previous SST concepts, learn about supersonic aerodynamics, consider what new technologies to apply, and then make your own concept sketches. Then, evaluate them, choose the best, and make a real design layout.
That is the process you should be learning at the undergraduate level. My book can help.
Good luck, and stop waiting!
January 27th, 2009 at 12:24 pm
Mr. Raymer,
Congratulations for your the excellent contributions to the field of aircraft design and specially for your effort in spreading the knowledge. Your books, software and courses are really great!
Currently I am searching for the best master degree program on the USA that focuses on the field. Based on your experience, could you please recommend me some options?
I will deeply appreciate your help and suggestions.
Hope to hear from you soon.
Thanks in advance,
Francisco.
January 27th, 2009 at 12:46 pm
Hello,
I suggested a few schools for graduate studies at
http://www.aircraftdesign.com/ray-rule-wouldbe.html
More schools are listed on my Links page at http://www.aircraftdesign.com/other.html#Heading6
Good Luck!
February 13th, 2009 at 1:55 pm
I am a senior in high school with the hopes of becoming an aerospace engineer. I have looked at your site and its incredible. I am still trying to decide if this is something I should, or even could, do. Obviously, you enjoy yourself. If you could answer a couple of questions for me, it would be extremely helpful.
What, in your opinion, is the most important trait a person must have to be an aerospace engineer? What is a typical day like for you? How difficult is it to become an aerospace engineer?
Anything you have to say would be appreciated.
Thanks a lot!!
February 21st, 2009 at 9:30 pm
(Disclaimer - I’m not Dr. Raymer.)
Sarah, FANTASTIC - Make it happen! I’ve been an AE for 20+ years and would humbly like to offer you my thoughts. First, there are many kinds of aerospace engineers: you don’t need to study “aerospace engineering” per se (e.g., AE, ME, EE, CE, Matls Eng, Physics, Mathematics, etc. grads all work in the industry). Second, your abilities and your interests will determine what job you’ll eventually do. For example, when I was in school I initially thought stability and control was the coolest specialty. I quickly learned I didn’t really have the math skills to do that work. As another example, I believe your hardwired personality traits will drive you toward - or away from - a management career track (vs. a technical path).
So let me offer MY answers to your questions…
>Most important trait (if I can pick only one): Desire and ability to virtually/mathematically model EVERYTHING having to do with an air- or space- vehicle. (That can be more fun than it sounds.)
>Typical day: You need to know that only a tiny fraction of AEs get the opportunity to do what Dr. Raymer does. 99% of us do not get to design or even significantly influence the overall design configuration of a new aircraft. Look at the bulk of current job openings: systems engineers, stress engineers, airframe designers, etc. In the 40’s 50’s and 60’s there were lots of new aircraft programs. Then things got more complex and expensive and time consuming, so new programs have become fewer and farther between. You now have alot of upgrade programs: F models, G models; we’ll add this radar and that advanced avionics suite; we’ll improve the manufacturability of this old bird; we’ll design a new wing for that workhorse. Also, the current fashion is for companies to outsource to - and team with - other companies. This means coordination and communicating with lots of different folks. If you are a good designer, you’ll spend your days sitting at the computer designing a part, assembly, interface, or mechanism. If you are great in math, you’ll do flight mechanics, aerodynamics or structural dynamics and write and run sophisticated computer code. If you’re a decent engineer AND a people person, you’ll manage subcontracts and projects and teams. If you take the management path, you’ll spend a lot of time managing schedules, costs, customers and management.
> Difficulty: If you like math and the physical sciences and are reasonably proficient academically at these disciplines, and if you have a desire to do engineering work, it’s not that difficult. Let me mention, though, that college is orders of magnitude more difficult than high school (at least it was for me). So you will work harder than you have ever worked before. I would say that it’s not that hard to be an AE, but it does require a strong work ethic and lot’s of discipline to be a GREAT AE.
Anyhow, that’s my 2 cents. Best wishes for a bright and shining career!
February 24th, 2009 at 8:58 am
Sir,
Have you written any new books on aircraft design. I am awaiting one from your end. Any new technical papers you have published recently. Let me know.
February 25th, 2009 at 1:13 pm
Hello Dr. Raymer
I want to Know what is relationship of engine performance with direction of captured flow? Is it important in design process?
Thank you.
February 26th, 2009 at 8:51 am
It would be better to put the answer and questions in decending order than ascending order.
March 2nd, 2009 at 2:05 pm
I purchased your book, Simplified Aircraft Design, and the RDS-STUDENT software through Amazon.com. The software was advertised as compatible with any DOS or Windows PC.
Neither I nor a hired computer expert cn load it on either of two Windows XP machines. The screen goes to a solid blue with a white rectangle near the upper right corner and freezes.
Amazon won’t refund money for software after the packaging has been opened. I couldn’t tell that it was defective or incompatible unitl I opened and tried to load it.)
Can I return it to you for a refund?
Hal Dantone
March 2nd, 2009 at 4:35 pm
Answers to recent postings (Disclaimer - I am Dr. Raymer.)
Sarah asked about being an aerospace engineer:
DPR reply: Probably the most important trait you need is a real love for airplanes and spacecraft. If it isn’t fun, don’t do it. You also have to be a bit smarter than average, and work a lot harder than average. It isn’t impossibly difficult to become an aerospace engineer, but it takes a real commitment – as do all good things in life. For my advice to people in your position, see http://www.aircraftdesign.com/ray-rule-wouldbe.html. Ezra’s comments are very good – thanks, Ezra!
SNSRAO (?) asks about any new books:
DPR reply: Not done yet, but I’m working on an introductory text on Aeronautics and Astronautics at the high school level, and an introduction to Spacecraft and Launch Vehicle Design at the upper college level.
Arash asked about direction of captured flow:
DPR reply: I’m afraid I really don’t understand the question. Do you mean a skewed air intake or something like that?
SNSRAO suggested descending order for these posts:
DPR reply: But then the answer would be before the question.
Hal Dontone has problems with RDS:
DPR reply: On the first print run of the RDS-Student Version 5.1 CD-ROM, the INSTALL program won’t work because the program files were inadvertently put into a subdirectory named “RDS-Stud51″ which has more than the 8 characters permitted for a DOS-based program. To install RDS, first create a new directory for RDS (C:/RDS is suggested - the name must be only 8 alphanumeric characters and with no spaces). Copy all of the files from the RDS CD-ROM into that RDS directory (in Windows use MyComputer or Windows Explorer). If your CD-ROM has the RDS files in a subfolder, do not copy by selecting the subfolder on the CD. Instead open that subfolder and copy all of the individual files (Ctrl-A then CTRL-C, go to the destination folder and press Ctrl-V). See http://www.aircraftdesign.com/rdstips.html for more tips.
I see that you bought RDS-Student and my “Simplified” design book. RDS uses the methods of my full textbook Aircraft Design: A Conceptual Approach and you may find it difficult to figure out without that book, or at least familiarity with those methods.
Sorry, I can’t refund what you bought elsewhere. But, stay in touch and we’ll get your installation working!
March 4th, 2009 at 10:52 am
I’ve been involved in building and flying radio controlled model airplanes for some time and have a question related to propeller driven aircraft. Many modellers build right thrust into their planes in order to compensate for the effects of engine torque, P-factor, etc. Most model aircraft do tend to turn left due to these effects and some amount of right thrust seems to help. I thought I had heard that full size aircraft have the same issue and that some prop airplanes a also designed with right thrust offsets. Is this correct and what light can you throw on this topic?
March 10th, 2009 at 9:26 am
Is it advisable and mandatory to increase the internal fuel tank capacity of a fighter aircraft if it is proposed to be fitted with a higher trust engine to enhance the performance of the aircraft? If yes, will it not become a new aircraft altogether with many changes. How best to avoid many changes.
March 10th, 2009 at 10:04 am
Jerry Kelley asked about engine mount offset:
DPR Reply: Yes, some real airplanes do use the same technique. The problem is, the to-the-right yawing moment this gives you should match the to-the-left moments you are trying to counteract, but they change differently with speed and angle of attack. So, you’ll probably need to use some rudder trim as well. But, I think an offset engine mount is uncommon for manned airplanes. The P-51, which had tremendous problems with torque on takeoff, had a slight downward pitch angle for the prop but no yaw angle.
SNSRAO asked about adding fuel tanks:
DPR Reply: Advisable - maybe. Mandatory - no. As you point out, the redesign effort can quickly escalate out of control….and budget. It is more common to add external fuel tanks than to try to stretch a fighter enough to pack in more fuel.
March 30th, 2009 at 1:43 pm
Thanks so much Ezra, your comments were very, very helpful!!
Thanks also to Mr. Raymer. You both were great help.
April 14th, 2009 at 4:54 am
sir,
i’ve got a trouble for understand principle of laminar flow control, so, please
tell me that stuff and physical principle ??
thank you..
April 16th, 2009 at 4:59 am
Laminar flow control is a bigger subject than I can handle in a quick blog reply, but here is an overview. There are two approaches - passive and active.
Passive basically means shaping and surface finish. We use good design practice and fancy computer programs to shape the surface to keep the pressure reducing as you go from front to rear for as long as possible. Obviously, you can’t keep reducing pressure all the way to the back so there is a limit. A super smooth surface finish helps a lot, also we must avoid any cracks, gaps, or other discontinuities. Even a dried bug splatter will cause laminar flow to become turbulent.
Active laminar flow control usually means suction. We put tiny holes or slots across the skin, about where the flow wants to become turbulent, and attach a suction pump to draw off the boundary layer. Obviously this adds penalties of weight and internal volume, and so far has not proven to be worth the trouble.
There are other exotic ideas out there that I’ve heard of, such as compliant skins, but I don’t know if any of them have been proven out in practice.
That’s a brief overview - do an internet search for more!
April 17th, 2009 at 5:19 am
thank for your answer sir.
actually i had bought your book, aircraft design : a conceptual approach. and it’s very useful for me to understand my college.
sir, can i ask you the last question..
we knew that space ship one had reached space approximately 50,000 feet altitude, but why it don’t use ceramic tiles ? we know space shuttle use ceramic tiles to protect re-entry thermal. so, What kind of materials did space ship one use ??
thanks a lot..
hagorly m
bandung institute of technology
indonesia
April 17th, 2009 at 5:47 am
Burt Rutan’s SpaceShipOne is sometimes described as a “champagne cork”. It goes up, it comes down. It doesn’t reach a fraction of the speed required for orbit, and when it reenters, it never goes fast enough to need ceramic tiles. Burt’s clever pivoting wingtip tails ensure that the body reenters at 90 degrees to the flight direction providing maximum drag as soon as possible, which reduces speed even further and prevents most heating.
When Burt does an orbital vehicle such clever tricks won’t be enough. He’ll need some sort of thermal control system. This could be tiles, blankets, or something more exotic like a water spray or heat pipes. Or he could carry enough propellant to basically stop the vehicle in its tracks and let it drop like SpaceShipOne. All of these have their own penalties.
Or, he may - once again - think of a completely new approach. He’s a fun guy.
April 24th, 2009 at 11:10 pm
Hello Dr. Raymer
I want to know about changes in engine performance during pull-up or push-over maneuvers. Please tell me a reference for further information.
Tank you.
April 25th, 2009 at 7:17 am
I’m not aware of a change in engine performance during pull-up or pushover. The only effect is an increase or decrease in load factor (”G’s”) and that shouldn’t affect thrust, I think.
April 25th, 2009 at 5:45 pm
Hello Dr. Raymer,
I have started kit/scratch building a popular low-wing, 2-place, metal, LSA type airplane. (Unfortunately it’s been in the news lately because of *possible* flutter-caused wing failures, but that’s another topic and I’m sure all will be resolved soon.)
I love the look of the Ercoupe and other H-tailed planes and am considering replacing the all-moving but otherwise conventional rudder with an H-tail configuration, just to be ornery I guess. Unfortunately I haven’t found much design information about this type of tail. Control linkages will be more complex, and weight will probably go up, but not being an engineer I’m not sure about other issues like drag, structural strength, vert. tail area, etc.
The Ercoupe is practically the same size and configuration as my plane, but I also have been unable to get details or drawings of the tail design.
1. Does your textbook have useful information on the H-tail? (You didn’t cover it in your homebuilding book!)
2. Can you point me to other references on the H-tail?
3. Same for the specific Ercoupe tail design?
4. Trick question, what do you think of an H-tail for a small single-engine low-wing plane? (Obviously this tail isn’t very popular, so the drawbacks must outweigh the advantages… but sometimes aesthetics are important too!)
April 26th, 2009 at 6:37 am
My textbook discusses the H-tail and many other tail configurations. As you said, weight will go up, ditto control complexity. You may introduce flutter problems too. Structural design will be an important issue - do it right or die!
Generally I recommend against modifying a kit or plans-built design, as stated in my book Simplified Aircraft Design for Homebuilders.
April 26th, 2009 at 3:19 pm
Thanks, I will get your textbook and the student version of your software. I have Simplified Aircraft Design and really like it.
*Everyone* recommends against mods, with excellent reason!
Whether I end up doing the mod or not, I view the workup as a good exercise to gain more knowledge. I use Solidworks at work, so I can model sheetmetal assemblies and do some simple stress modeling.
My plane will also incorporate a BRS parachute, even if it’s built strictly to the drawings.
Thanks again for the response.
April 27th, 2009 at 8:16 am
By the way, I was not being sarcastic… if someone asked me, I would recommend against modifications too.
June 17th, 2009 at 2:02 pm
Dr. Raymer,
I am 28 years old and I am considering a career change. I have a Bachelors in Architecture from Florida Atlantic University and I have been in the Architecture field for about 5 years now. When I entered college I really wanted to go to Embry-riddle, but I did not have the money to go there and neither did my parents, so I changed my major. I am not too strong mathematically, but I do understand the principles of aircraft design pretty well overall. Ever since I could remember, I have drawn airplanes. I have built and flown 8 R/C airplanes from kits and I have designed 5 R/C airplanes (not counting unflyable kits I have thrown away…LOL). I hope to sell them as kits as soon as they get finished (even if I don’t make money selling, who cares, I loved designing and building them). Anyways, this is something I absolutely love doing and I have thought of going to work for an airplane manufacturing company or design company. Is it worth changing career paths right now? Or is it a bit late?
June 23rd, 2009 at 1:53 am
Robert,
If, tomorrow, I woke up in exactly your situation in life, I’d go for it. If you love airplanes and aircraft design as much as I do, then make it happen. Probably the best path would be to get some education in the field, preferably a Bachelors or Masters in Aero Engineering. Your experiences as an Architect are applicable. A lot of what we do is really “aircraft architecture.”
On the other hand, if you are making a fortune as an architect, don’t give it up! Instead, teach yourself aircraft design in your spare time and then design and build the world’s best homebuilt.
Regards,
Dan Raymer
June 29th, 2009 at 10:11 am
Dr. Raymer,
My goal is to work for a small company that designs and builds home built/small single/dual engine aircraft. I wanted to ask another question, I read through your website on all the “wanna be” sections and I was wondering, what specific skills should I emphasize on my resume? Should I learn solidworks/inventor? Which is more popular for the Aviation industry? Catia? I am currently an AutoCAD instructor/customization expert, so I have a pretty good hold on that. Should I attach my R/C Aircraft designs to the resume? How do I catch the eye of the companies reading my resume?
I can’t wait to see you at OshKosh! I am attending all your lectures.
June 30th, 2009 at 1:34 am
Different CAD systems have very vocal fans. CATIA tends to dominate the big companies, but ProE, Solidworks, Unigraphics, etc… are used as well. AutoCAD isn’t used much in aircraft design, so get some experience in others, probably CATIA and one of the other three listed above.
But the CAD system you use is less important than your technical abilities, so I think you’ll need some engineering training too, unless you just want to be a “hired gun” CAD jockey. Nothing wrong with that, I have a great guy with a small company doing just that. I hire him to take my designs and put the solid model polish on them. But he doesn’t design my airplanes.
Yes, show RC designs, but don’t let that seem like your main accomplishment.
Best of luck
Dan
July 2nd, 2009 at 8:08 am
Dr. Raymer,
The other day, one of my colleagues commented that most new US and Russian designed fighters seem to use a convential wing/horiz stab configuration with twin vert stabilizers (e.g., F-22, F35, F-15SE - albeit Suhkoi is also adding canards), while the newer european fighters use a delta wing/small canard/single vert stab configuration (e.g., Typhoon, Gripen, Rafale).
Care to comment on what is driving this difference in fighter configuration?
July 6th, 2009 at 1:48 am
Hello,
If you could provide an example of where and how you would perform an iteration on your ASW sizing calculation from page 31: Aircraft Design.. Specifically on the first portion when calculating the Cruise:
W3/W2 = e{-R/CVL/D} = - 0.153 = 0.858
The Breguet equation was simple enough but the figure at the end(.858) is a problem. Also read earlier for this same issue where you mentioned just to iterate until they are off by a small amount - 0.1%(computer) or 1% manually. (I’m mediocre at math at best.). I NEED to get pass chapter 3. I won’t bother you again (or at least until I get to chapter 6). Appreciate it.
July 21st, 2009 at 9:32 am
How does the fighter aircraft performance affect when different engine axis orientations with respect to longitudinal axis of aircraft are studied during the layout stage ?
July 26th, 2009 at 10:17 am
Hello Mr Raymer,
I am a mechanical engineering student. I would like to know which university is better for Masters program in Aricraft Design ?
1. Cranfield University
2. University of Manchester
August 7th, 2009 at 8:10 pm
hello sir
i am a 17 year old boy from mysore, india. remember sir when you came to
mysore with our dads car to explore mysore palace and other places. i met you rite there sir and i was so exited. that was when you gave me those books of aircraft design
sir i have read the books you gave. those are fantastic sir
August 7th, 2009 at 8:12 pm
sir you can reply me on ice_vishwas@yahoo.com
from vishwas mysore.
August 10th, 2009 at 2:18 am
Hell Vishwas,
The email address you provided doesn’t seem to work. Please email me at the “send message” button at www.aircraftdesign.com
It is wise not to post email addresses on web sites - you will be attacked with spam !
Daniel Raymer
September 9th, 2009 at 2:28 am
Dear Sir ,
I have been an avid follower of your work for some time and I would have to say that you and rotan have had a huge impact on my career, now to business.
I currently work at an MRO station in their engineering department and have work on many things from (Aquiring an STC of modifcation work on the aircraft structure and interior , actual engineering modifcation and fabrication of many aircraft components some times even to a point to designing improvments and also designing and overseeing the technical aspect for an alocrom facility as well as many other things )
Now for my actual inquiry(sorry for the long introduction) I am seeking out a Masters degree but I dont know what or when I should do it ive always have a knack for designing aircraft ? so should I just quit my job and travel across the atlantic to take that degree or should I wait a couple of years and garner more experience or even if possible take it online
Thank you so much
Regards,
Kareem
September 13th, 2009 at 6:39 am
Hello Dr. Raymer
Please explain me what is the impact of “rate of change in thrust” on initial design phase and how we can estimate this parameter for turbojet engines?
Thank you very much.
September 20th, 2009 at 3:07 pm
Dr. Raymer
Can you give me a rough estimate of how much aircraft weight with the requirement of 2 hour endurance, stall speed 15ft/s, take off less 30ft distance?
October 3rd, 2009 at 7:52 am
Hi Dan,
Have you flown any r.c. (”hobby sized”) aircraft ?
I started a discussion here, asking for a “ballpark” estimate of climb rate for an r.c. heli :
http://www.rcgroups.com/forums/showthread.php?t=1110121#post13260378
As you may or may not know, r.c. helis are grossly over powered. I’ve read where ~90 watt/lb is adequate for hovering. Most of the current r.c. “3d capable” helis have power systems delivering 500w/lb or more !
The latest formula I was given was :
climb rate = (power in -power to hover)/weight.
Ok, a 2 lb heli, needing ~100 watt/lb.
Full power it puts out ~600 watts.
So power-in=600, power-to-hover=200 = 400 w / 2lb = 200(units??)
What are the climb rate units? … m/sec ?
200 m/sec = 39,370 fpm, which seems a “bit” high !!
Mike
October 4th, 2009 at 7:23 am
Dr. Raymer,
Is it feasible for a patient, talented amateur to consider building his own design airplane from ‘carbon fiber’? If so, can you recommend any books or other resources?
Thanks!
October 4th, 2009 at 8:05 pm
Dr. Raymer,
Hi I’m a senior engineering student working on my capstone project and I’m going to design and build a UAV. I bought your Aircraft Design book to help me, since my degree is not in aerospace and have not had courses to help other than Fluid Mechanics. I’ve just started reading and working on my project. I’m just wondering if I’m how much trouble I’m going to run into designing a small UAV (around a 10 ft wing span) by following your book? For example, sizing, for a design takeoff gross weight equation (3.4) I would get zero because I’ll have no crew and no payload. I’m sure there is a way or different equation. I’m just wondering if you have a book for more of what I’m doing or if and can continue with the book I have with minor changes I’d have to make.
Thank You in advice for your time.
Toby Sorensen
Senior Integrated Engineering Student
October 4th, 2009 at 8:15 pm
Also, how much would your RDS program in my case be of help?
Thanks
October 24th, 2009 at 3:38 am
Hello Dr. Raymer,
Can you recommend an books which detail the design history of classic WW2 vintage warbirds?
I’m interested in books similar to “Superfortress” by Curtis LeMay, that discuss technical issues, and design and program trade offs.
It appears that we went from production of relatively mediocre aircraft in the pre war period, to production of best in class in a single design generation. There should be some valauble lessons in that history.
Best regards,
Mitch Funk
November 12th, 2009 at 8:06 am
Hello Dr. Raymer,
My family and I met you and your father at the EAA airshow this summer. My son, Michael, was the one who helped you with your powerpoint presentations. We just purchased your new book as a Christmas gift for Michael and I was wondering if you wouldn’t mind autographing the book and a photo from the airshow for Michael. Coule you please e-mail me at dspencer@icsystem.com and let me know if you’re able to do this? Thank you. By the way, Michael and I are both in ground school now and will be starting flying lessons soon - he still wants to be an aircraft designer. Thanks, David
November 21st, 2009 at 11:23 am
Hello Dr. Raymer,
Could you point me to the best source for published, post-WWII military aircraft performance envelope charts or data? I’m working on an update for a historical simulation with educational and commerical application. A new tactical scale proposed for the simulation will require accurate representation of individual aircraft movement using mach, altitude, deg/sec, g limitations, load, etc. Cost is, unfortunately, an issue, but not necessarily prohibitive.
Thank you for any information you have in advance, and thanks for the opportunity to contact you directly via your excellent web presence.
Best regards,
Douglas Grant
December 5th, 2009 at 5:27 pm
Error problems - I had an error 53 in the design layout. Before I read on your site that there was initial bug and that I needed to install the newest version of RDS, I deleted the RDS directory. I then created a new RDS director and installed the newest version of RDS. I have Windows Vista and am using DOSBOX version .73 to run the RDS program. After the initial settings for units and printer I am getting the following error:
Error 53 at pgm-ctr: 802184
What should I do?
Thank you,
Michael
December 8th, 2009 at 5:15 pm
Nevermind - I figured out the 53 error
Michael
December 22nd, 2009 at 12:39 pm
Dr. Raymer,
I am beginning to put pen to paper in developing a 2 place high speed homebuilt with sufficient range to travel from coast to coast. I am currently commuting across the nation every two weeks and would prefer to do the flying myself. I have a 172 which doesn’t quite fit the bill. I’ve looked at the Lancair IV and IV-P as an option, and it would be a very good airplane. But, I would like to be a bit faster, and don’t have need of four seats. My original thought was to use the basic design of the Lancair 360 with the engine and prop from the IV to see if I could get a TAS of 390 Kts (450 MPH, that magic number for propeller performance). In looking at doing this though, the increase in power alone won’t come close to the performance I was looking for. Also, in looking at the propeller, it is apparent that to keep tip mach below 1.0, a geared engine would be required. This led me to select the Continental GTSIO-520-N engine, developing 375HP at a prop RPM of 2235 and driving a Hartzell HC-H3YN-2UFX/FC7291 prop to produce a tip mach of .968. This would provide me with a thrust of 267 Lbs (85.4% propulsive efficiency), which fits with my required L/D of 15:1 and a gross weight of 3100 Lbs. I will be buying your book(s) as I go forward. I think that I can achieve a low enough drag figure, but thought I should ask someone who is more qualified to let me know if I’m crazy or not. Have a wonderful Holiday and a very Happy New Year. - Ken Anderson
January 18th, 2010 at 3:46 am
Dear Sir,
I am doing a conceptual design of an aircraft and i want to know whether there is a direct method to select airfoils from a lobrary of airfoils and check them for the CL, L/D and mach critical directly and give me the best airfoil i can use. I am curretly doing the anlysis on xfoil and can do it individually for airfoils one by one and then select them by comapring them. Is there a way to automate in matlab and get the best airfoil for the particular wing span position.
I also have another question : if i am designing a BWB , and want to select an airfoil with a thickess of 18% w.r.t chord. is ther another a way to select an airfoil and change the coordinates without using the equations descrbing that airfoil. i.e . if i have corniates for NACA 4415 and i want to increae the thickness and move the thickness point from 30 to 50 % of the chord. and then analyse it on matlab.
If you have any such report pls do post it. i will be eagerly waiting for it.
I dnt want to optimize airfoils but want to use existing coodinate files to do the design.
January 30th, 2010 at 11:26 am
Hello, All. Sorry I haven’t answered for a long time. I’ve been finishing my new book (hope you all have ordered it!), then it was the holidays, and then I had to do a lot of work to catch up. But here are answers to your excellent posts:
Kareem said: I am seeking out a Masters degree … so should I just quit my job and travel across the Atlantic to take that degree or should I wait a couple of years and garner more experience or even if possible take it online
Raymer’s Reply: A job is a wonderful thing to have – unless it stands in the way of your dream. I can’t advise you on that. But, if you really want to work as an aircraft designer you need the right education, and the right experience. If you can go to one of the “premier” aircraft design universities that is best, but any university with a solid engineering program can give you the basics, and you can probably do some independent study (use my book!) to get the aircraft design part. Best of luck!
Arash Said: Please explain me what is the impact of “rate of change in thrust” on initial design phase and how we can estimate this parameter for turbojet engines?
Raymer’s Reply: Hmmmmm… I’ve never heard of anyone worrying about that, these days. Early jets took a long time to spool up from a low thrust setting, but modern jet engines are quick. Better ask a propulsion expert if this really is a concern to someone.
Tuan Nguyen Said: Can you give me a rough estimate of how much aircraft weight with the requirement of 2 hour endurance, stall speed 15ft/s, take off less 30ft distance?
Raymer’s Reply: Sure – through a paid consulting contract. Sorry, but that isn’t something you can guess off the top of your head. I do it for a living.
Gene Kahn Said: Is it feasible for a patient, talented amateur to consider building his own design airplane from ‘carbon fiber’? If so, can you recommend any books or other resources?
Raymer’s Reply: Sure. Peter Garrison (Flying magazine) did it, and his plane Melmoth 2 is gorgeous. See my website for book recommendations.
Toby Sorensen Said: (question about how you do sizing for an airplane with no crew and no payload)
Raymer’s Reply: Obviously, the equations fall apart at the ridiculous minimum. For such a design you’d probably just pick some small engine, wrap an airplane around it, and calculate its performance. In other words, forget classic “sizing.” RDS would help with the analysis but don’t use the sizing calculation, instead use RDS for fixed-size range estimation.
Mitch Says: Can you recommend an books which detail the design history of classic WW2 vintage warbirds?
Raymer’s Reply: I’ve read various books about specific WW2 planes, but not an overview.
David Spencer Said: My family and I met you and your father at the EAA airshow this summer. My son, Michael, was the one who helped you with your powerpoint presentations. We just purchased your new book as a Christmas gift for Michael and I was wondering if you wouldn’t mind autographing the book and a photo from the airshow for Michael.
Raymer’s Reply: (FYI lurkers, I sent Michael an autographed copy of “Living in the Future: the Education and Adventures of an Advanced Aircraft Designer” to thank him for his help. Great kid, with a promising future in our field!)
Douglas Grant Said: Could you point me to the best source for published, post-WWII military aircraft performance envelope charts or data?
Raymer’s Reply: The USAF used to publish “SAC Charts” (Standard Aircraft Characteristics) which were very useful. I don’t know where to find them today – eBay? FOI request to WPAFB? Beyond that, there is Janes, AvWeek, and the internet.
Michael Says: (problem with RDS) Error problems - I had an error 53 in the design layout….
Michael Says: Nevermind - I figured out the 53 error
Raymer’s Reply: Some times problems just go away……..
Ken Anderson Says: I am beginning to put pen to paper in developing a 2 place high speed homebuilt with sufficient range to travel from coast to coast…
Raymer’s Reply: Sorry, I just can’t comment off the top of my head for such a detailed engineering question. It would take hours, or days. I do this for a living. Best of luck, though!
Anonymous Says: I am doing a conceptual design of an aircraft and I want to know whether there is a direct method to select airfoils from a library of airfoils and check them for the CL, L/D and mach critical directly and give me the best airfoil I can use. I am currently doing the analysis on xfoil and can do it individually for airfoils one by one and then select them by comparing them. Is there a way to automate in matlab and get the best airfoil for the particular wing span position.
Raymer’s Reply: These days most professional aircraft designers use airfoil design programs to design custom airfoils, optimized for the design and the mission.
February 17th, 2010 at 8:20 am
I’m a student currently ‘designing’ a Jet transport. and I’m following the Initial Sizing Chapter in your textbook.
I’m looking at table 6.1 and I’m uncertain what values of T/W0 and W0/S I should use in the equation.
Is the T/W0 and W0/S determined by a fixed value?
(I’d Set T/W0=0.21 and W0/S=120)
Or is it dynamic in the iteration process, using a fixed T and fixed S?
(As W0 changes throughout the iteration, T/WO and W0/S will change)
I’m also going to account for a composite/future materials and multiply the We/W0 fraction by 0.9
In your examples in Chapter 23, it seems you used your ‘design’ T/W0 and W0/S into the equation….simply: what T/W0 and W0/S should be considered in the empty weight fraction equation in Table 6.1? (page 113)
March 22nd, 2010 at 10:00 pm
Wait a minute. “Simplified Aircraft Design” but you won’t give us any derivations or proofs? How are we supposed to remember any of it five minutes after closing the book? With no derivations or proofs, if you forget one little piece it’s gone. With them, it’s easy to fill in the blanks. I’ll probably buy the book anyway, because everyone seems to like it. And perhaps I can remember it anyway, though that was a nightmare in differential equations, where they would just give you the recipe and not how it worked. I’m the kind of guy, or used to be, who couldn’t remember the formula for the volume of a sphere, but could derive it faster than figuring out which nearby book it was in. Also hoping there are some rules about how to think about non-standard configurations, very low AR, etc. No point in designing what’s already been done a gazillion times. Five or ten times, ok, but not a gazillion.
March 25th, 2010 at 6:01 pm
dear dan, i could not find an email 4 u on your sites .. anyways, i have 4 unique designs in my head that need development, simulation, scale-fabrication, and full-fabrication. i know there are flight simulators that allow implantation of custom designs but.. i need to correspond with you about universities, design sw, simulation sw,.. so plz let me know how i can contact u directly.. i have several questions indicated above.. i am also hooked on hg, flight in general, spaceflight, commercialization of space, and various other space-related categories which i’m sure you have an interest..
March 26th, 2010 at 12:47 am
Hello Dr. Raymer.
I now own your book “Aircraft Design: A Conceptual Approach”, and I have to say that I am very satisfied with it. It has helped me a great deal in understanding the many aspects of the conceptual design of aircraft. I’m not even a student of this field and I still get enjoyment out of reading your book.
I am quite curious as to the design featured on the cover of the book (which you refer to as the Rockwell ATF concept). I realize that you are probably not allowed or able to publish all data about this design, but I would be interested if you could help answer some of my questions regarding it.
1) Did this particular design (as well as the “Revised Rockwell ATF Concept” as shown on the page of your website entitled “Aircraft and Spacecraft Conceptual Design Drawings & Pictures”) have an official designation or number that it was referred to by within Rockwell?
2) I’ve read somewhere (the exact source I cannot remember) that this design was thought to be capable of supercruise based on wind-tunnel models. Of course, not just any engine can provide supercruise. I do not know if the Pratt & Whittney F119 had been conceived of at that time or not, so do you know what engine(s) those calculations were based on?
3) Would the wide spacing between the engines have posed a serious problem in the case of an engine flame-out? Would it have remained controllable?
4) One of the things that stands out to me the most about the design is the lack of stabilators/horizontal stabilizers when almost every other modern fighter jet has either those features or canards. Despite this, was it determined that the aircraft would have competitive pitch authority and/or turn rate when compared to a more conventionally-designed fighter?
Other than these questions, do you know where I can learn more about this design?
Thank you for any response.
March 29th, 2010 at 1:58 pm
More accumulated questions and Raymer Replies:
Joe Says: I’m looking at table 6.1 and I’m uncertain what values of T/W0 and W0/S I should use in the equation.
Raymer’s Reply: These are preliminary estimates as described in Chapter 5.
LR Says: Wait a minute. “Simplified Aircraft Design” but you won’t give us any derivations or proofs? …….
Raymer’s Reply: That’s why it is called “Simplified!” For the whole story get my textbook, all 838 pages of it.
Sam Micheal Says: i could not find an email 4 u on your sites .. anyways, i have 4 unique designs in my head that need development, simulation, scale-fabrication, and full-fabrication….
Raymer’s Reply: There are several places on the website to email. They’ll get to me. As to unique designs in your head, I’ve said it many times before that I can’t get involved in such things except as part of a paid consulting contract. Sorry. Legal issues, and also I do this for a living and am already grossly overworked. Wife and kids need some time too!
Lance Bradshaw Says: I now own your book “Aircraft Design: A Conceptual Approach”, and I have to say that I am very satisfied with it…
Raymer’s Reply: Thanks!
…I am quite curious as to the design featured on the cover of the book…
…1) Did this particular design…have an official designation or number that it was referred to by within Rockwell?
Raymer’s Reply: Internally it was design D703-11. It never got a real DoD designation because it (actually a later version) didn’t win a YF fabrication contract (YF-22 and YF-23 were the winners)
…2) I’ve read somewhere that this design was thought to be capable of supercruise based on wind-tunnel models. …
Raymer’s Reply: Absolutely true. Fantastically low drag, proven in supersonic wind tunnel tests.
…3) Would the wide spacing between the engines have posed a serious problem in the case of an engine flame-out? Would it have remained controllable?
Raymer’s Reply: Yes, at normal angles of attack. At extreme angles like 45 degrees you would have to quickly kill the thrust on the remaining engine until the nose was brought down.
…4) One of the things that stands out to me the most about the design is the lack of stabilators/horizontal stabilizers when almost every other modern fighter jet has either those features or canards. Despite this, was it determined that the aircraft would have competitive pitch authority and/or turn rate when compared to a more conventionally-designed fighter?
Raymer’s Reply: Yes. Validated by tons of wind tunnel tests, CFD, dynamic simulation,…..
…Other than these questions, do you know where I can learn more about this design?
Raymer’s Reply: Funny you should ask – there is a long chapter on this project in my new book, Living in the Future. See http://www.aircraftdesign.com/livingfuture.html. Believe me, anyone who asks such questions will enjoy this book!
April 2nd, 2010 at 9:39 am
Dr. Raymer,
With the introduction of the new T-50 from the Russia do you see any similarities with the designs you came up with for the ATF competition? Just wondering if you have taken a personal look at the design.
April 3rd, 2010 at 10:27 am
The T-50 doesn’t look like my old designs, but looks a lot like an “eyeball” copy of the F-22. It will be interesting to see what changes are made for the final production version, because the differences between it and the actual F-22 are not favorable in my opinion.
Pretty funny to copy a design that is already going out of production…..
April 21st, 2010 at 2:05 pm
Is there any way to run rds (a tudent verison) in batch mode? If yes, how? I am trying to help a user to run the program many repeats with different inputs. Thanks, Douglas
April 21st, 2010 at 9:04 pm
Running a program like RDS in batch mode is typically done to populate the design space in a big trade study. RDS-Student does not do such things automatically because I want students to learn to do trade studies by personally running the parametric variations through the code. In this way they will learn what is really going on when one does a trade study.
RDS-Professional has all the typical design trade studies automated - select the option and the results pop up. Automagic!
But to specifically answer your question - neither version of RDS supports batch mode at this time. RDS-Student never will, for the reason described above. RDS-Pro could be so coded (or a standalone calculation-only version could be coded) if a cusomer wanted to pay for it. But RDS-Pro already does all the essential trade studies automatically.
Please note that RDS-Student is for students. The license agreement forbids its use by companies for professional activities. RDS-Student is priced as charity for student usage. The price is way too low to support its continued development let alone pay for its coding in the first place.
April 22nd, 2010 at 7:05 am
Hello! Dr. Raymer.
I’d like to know if, without changing anything about a wing except the spar, we can transform a 1 piece solid wood spar into 2 piece spar with same g-load, by spliting the spar into 2 and joining them with appropriate steel plates (top and bottom) and joining them with appropriate bolts. If possible, do they (left and right) have to be in contact in the middle?
Next, can the spar be substituted by different design, lighter but with same g-load and in 2 pieces? I’m thinking in the range of +4.5 & -1.8 g (600lbs).
The original solid spar is like a board (thin and wide) lengthwise, except for the portion inside the aircraft body that ends in small portion outside on both sides of the aircraft wall. This is obtained by laminating 3 or 4 smaller boards.
Is there anything that forbids this way of thinking? Are there other forces in play that forbids these direct approach, with a concern only in the g-load?
For the substitute spar I was thinking a design in a slot-like-type-of-going-into-the-body spar, with possibly overlapping them or meet in the middle, which would keep the same g-load, and with easy fixture. For this last requirement the overlapping solution with 2 appropriate bolts would join both halves together (4 holes - 2 each) and to the aircraft body, keeping the appropriate dihedral.
Lastly, in a overlapping spar solution, the LE of both halves would be alinged or 1 half is ahead of the other? If it’s the first observation that means the ribs on both halves differs, by small amount, their position in the spar (LE to TE)?
Thank you
PS - Where could I find additional information on this that can teach me how to design the spar?
April 22nd, 2010 at 7:40 am
Manuel,
You put a lot of effort into your questions so I hate to say this, but I just can’t answer. What you are talking about is serious engineering work, not something I can “wing”.
There is a top-level overview of structural design in my Homebuilders book, and several good structures books are suggested at http://www.aircraftdesign.com/books.html#Tip5
Sorry, and good luck!
May 1st, 2010 at 11:20 am
Hello Dr. Raymer,
I am trying to design a twin engine turboprop aircraft with your textbook. How can I determine takeoff parameter from takeoff distance using Fig. 5.4 on page 99? It indicates BFL only for jet but not for propeller.
Thank you in advance for your help.
May 17th, 2010 at 1:52 am
Raymer Replies:
Manuel Says: …transform a 1 piece solid wood spar into 2 piece spar
Raymer Replies: You can do anything - but determining if it is lighter, stronger, and still safe takes some real engineering effort. I won’t reply to your specific questions both for legal reasons, and because it would take me a lot of time - days - to look at the design and form an opinion, then do some analysis to see if the numbers hold up. Sorry.
Yuki says:…twin engine turboprop aircraft …How can I determine takeoff parameter from takeoff distance using Fig. 5.4 on page 99? It indicates BFL only for jet but not for propeller.
Raymer Replies: As a guess, I’d use the Propeller lines and double the results for Balanced Field Length.
Perhaps somebody would like to extend this emperical method to apply to turboprops as an independent study class or perhaps a Master’s thesis. If so, get the original NACA/NASA reports and apply the same methods to turboprop data. It’d be fun, and useful to other aircraft designers. I’d include it in a future edition of my book.
May 25th, 2010 at 7:17 pm
I have the student RDS sotware & I have tried two computers , with no luck. The DOS test file does not work on either! HELP!
May 27th, 2010 at 2:17 am
Sorry for the trouble. First, please see the RDS Tips at http://www.aircraftdesign.com/rdstips.html. If you are running Vista or Win7, see http://www.aircraftdesign.com/rdstips.html#Tip3 for downloading DOSBOX to use as a wrapper for running RDS.
If those don’t get you running please email to me directly (top of the Tips page) and fully describe what is happening, what Windows version you run, etc…
June 7th, 2010 at 4:04 am
hello sir,
i am studying your RDS progam . its quit easier way to analyse but. I am finding difficulty in propulsion analysis. I am using DUAL SKY 3536-8-990 KV motor. Can we use electric motor for propulsion analysis? If possible kindly tell me how it can be done.
Thank you .
Have a nice day
June 17th, 2010 at 6:32 am
Hello sir,
I am currently studying BSC hons in Aeronautical engineering (UK) and your book has helped me a lot during the process. I have to choose a dissertation topic for my third year at university. I was thinking of doing a conceptual design of a supersonic transport but we have a module called aircraft design in the 3rd year and conceptual design of SST is a group design project set by the university. My personal tutor told me that it is not a good idea to do conceptual design of an aircraft as a dissertation as we would be doing a group project on the relevant matter.
Now i cannot really think of any interesting topic for my dissertation. I would be more than grateful if you please provide me with any interesting ideas and topics for my dissertation. Thankyou sir.
June 21st, 2010 at 8:22 am
Pranav - Electric motor itself is easy - put in horsepower and prop data, and you get thrust. The hard part is SFC - it is meaningless for an electric motor. Just put in a nominal SFC (=1?) then ignore SFC results. Don’t try to use the Sizing module - just determine how long the engine will run then multiply that times speed.
Renzo - a group project is not the same as doing it all yourself and really learning how it is done. If you really love design, do it. But…if you don’t go into the design field, you’ll be penalized accordingly! Maybe a better idea is to do design optimization, as I did for my PhD. See my Bio page for a link to my thesis.
June 23rd, 2010 at 3:16 pm
Dan Raymer,
Greetings. I wish to say that I just received your 4th edition design book with the accompanying software package from the AIAA and look forward to exploring both. In addition I hope that there will be opportunity to exchange notes on air and spacecraft design questions. But despite the bright horizons, I have encountered some implementation problems with the software thus far.
Looking at the design software handbook, I noted the instructions for installation for a Windows system, but I seem to encounter a cul-de-sac which involves instructions for setting up a directory for program files (e.g. RDSPF) and then a blue screen and small yellow square that can be maneuvered about a small portion of the screen with a couple of keys.
I am using a desktop HP system with 2 gigabytes of memory and larger virtual memory, motherboard circa 2005; so I don’t think it’s a question of sufficient memory or resources. Has someone else encountered a similar problem with a fix or an alternate approach?
Best regards,
Wes Kelly
June 23rd, 2010 at 4:15 pm
A follow-up. Program is loaded. There appears to be no basic problem other than that I veered off course on the configuration menu selections.
Best regards,
Wes Kelly
June 23rd, 2010 at 6:45 pm
Hello Dr. Raymer, it’s Lance again.
Your book describes the technique for determining tail volume for conventional layouts with tails or canards. However, I don’t know if it mentions the methods for unconventional designs such as those with aft-strakes/back porches. It might be there, but I might just have not seen it.
How might I go about calculating required moment arms for an elevator/elevon on an aft-strake? Should I consider the elevator area to be the equivalen to tail area on a conventional design?
June 30th, 2010 at 8:53 am
Don’t you have anything on seaplanes - something in the pipeline perhaps? I can’t do much with “Simplified” & the spreadsheet meantime. GF
June 30th, 2010 at 9:53 am
Raymer reply to Lance Bradshaw: Tail Volume methods are statistical, which means you need a large “sample size” to make an equation. By definition, unconventional designs do not have a large sample size. Do what I do - fake it on the Dash-One, and get some real analysis as soon as possible.
Raymer reply to Graham Fyfe: My big textbook has some material on seaplanes. Otherwise, see old NACA reports and if you can find them, reports from the David Taylor Model Basin.
July 22nd, 2010 at 3:57 pm
Hello
I have a quick question about the weight fraction methods for a cruise segment for a piston engined aircraft.
Looking at the worked example in the back of your 3rd edition, I can replicate this perfectly using british units but for some reason when I repeat the calculations using metric units, the sfc is an order of 10 too high to get the same results as for the british units.
I have reworked the calculations and derivations many time and get the same results each time. Is there a ‘g’ factor missing ?
Much appreciated
July 22nd, 2010 at 4:18 pm
Hello again
I was also wondering if you might be able to offer any advice on the best place to look for your first job as a conceptual designer after graduation.
I have spent the last few years working hard on my education to be able to land a dream role as a conceptual designer and now have the following qualifications.
- PhD in aircraft conceptual design from Cranfield UK
- MSc in aircraft design from Cranfield UK
- BEng in mechanical engineering from Loughborough UK
It seems that the hardest part is just starting, to try and land my first role. After searching high and low, I am under the impressoin that many of these jobs are filled by word of mouth and not necessaraly advertised. Any advice would be much appreciated.
Thanks again
August 9th, 2010 at 12:13 pm
Ady,
Metric units - you aren’t off by a factor of 10, but by a factor of 9.807 which is “g” in metric. This is needed since SFC in British units includes “g” but in Metric units, does not. This is mentioned in the front of the 4th edition of my book since it wasn’t clear in the 3rd edition. You should get the new one - much better in all regards!
Concerning career advice, see http://www.aircraftdesign.com/ray-rule-wouldbe.html. Best I can offer.
August 29th, 2010 at 11:43 am
Dr. Raymer,
I am an aspiring aircraft designer and have read your latest book and enjoyed it very much!
However, this message is for a different purpose.
My university aircraft design team is trying to find typical wing-loading numbers for hand-launched UAVs and RC aircraft for a project. I was wondering if you had any data on that or any contacts that could point us in the right direction? I have the latest copy of your AIAA-published textbook too so if there is a table or equation in there for us to use, I can find it given the chapter # too!
Thank you,
Thomas Gray
September 3rd, 2010 at 9:12 am
Dr.Raymer
Is the sloshing of fuel in fuel tanks an important design criteria in aircraft design. How do we estimate its effect on the performance of aircraft.
October 9th, 2010 at 8:24 am
Hello
What is your thoughts on the prospect of somebody actually landing a role a conceptual designer ?. Myself, I have ticked all the boxes academically (spent the last 10 years getitng all the qualifications) and tried get involved as much as I can but the propsect of working as a conceptual designer is still a distant dream.
My feelings are that of all the trained aerospace engineers out there, less than 1% actually work in conceptual design. Do you think that conceptual design is reserved for the elite few and homebuilders ?. These days I think that chasing after this dream can be likened to wanting to become a football star or rock star with very very slim chances. Do you think that young people should be be realistic before before they start out.
I don’t mean to sound so negative, I am just worried about young peole falling down the same trap.
Thanks
October 18th, 2010 at 8:12 am
Tom: The internet has all kinds of information on weights and wing areas of UAV’s and model airplanes. Also, there is the annual Source Book issue of Aviation Week which has tables of info on all types of aircraft including little UAV’s.
Akspas: Fuel sloshing is usually important only in the final detailed stability calculations, but when we make our design layout we think about it a bit and try to avoid an obvious problem, like using one huge tank from nose to tail or from wingtip to wingtip. Better to use a couple of smaller tanks.
Ady: It is true that of all the engineers out there, only a very small percentage actually work in conceptual design. But the odds are not as bad as you might think of getting in, because most working engineers don’t really want to work in conceptual design. They don’t have the creative temperament, they don’t love airplanes enough, and they don’t work hard enough to get there. No offense to them, and sometimes I wonder why I’ve worked so hard at it - and then I remember how fun it is to me and how, if I did something else for a living, I’d design new airplane concepts just for fun!
Besides, if you try to become a conceptual designer but just don’t find your way there, you can always work in detail engineering design, testing, or something similar, making darn good money, while keeping your eyes open for an opportunity. Such detailed engineering experience will make you a better conceptual designer in the end. All good, either way.
October 18th, 2010 at 5:18 pm
Thanks. I think the main problem in my own career is that I am from the UK where there are lsignificantly less opportunities than in the US. Also it is proving impossible to land a role within a US company as I am not a US citizen. I think geographic location is very important.
Another interesting question I have for you.
I have learned very early on in my career about how plagiarism is a particulary bad problem for all engineers. It was a particular problem for the Wright brothers, Frank Whittle and many more. It is possible to apply for patents to stop other companies using the ideas but it becomes more of a problem when it is work collegues within an organisation.
Myself, I have lost many a nights sleep, risked my health and relationships and put blood, sweat and tears to rescue a well publicised university project, only to have suffered at the hands of senior staff eventually passing my work off as their own. Being early on in my career I did not having sufficent standing to be able to voice my objections.
Have you come across simular problems in your career and how did you deal with the situation ?
October 18th, 2010 at 6:54 pm
Truly an interesting question…
First of all, it is very difficult to make any money off an idea for a new aircraft concept. No big company will pay you - they want their own engineers to come up with their advanced concepts. You can try to patent it but even a slight change in the concept will allow lawyers to invalidate the patent. Your new idea will become just a part of the “state of the art” floating around out there that others will use to come up with their concepts.
If you want to get rich from an aerospace patent, you should come up with a new way to set a rivet or post-cure a composite material, not invent an all-new aircraft design.
As far as “bragging rights” are concerned, your story is all too common. I’ve had a number of my original new ideas “appropriated” by others, who actually seem to believe that it was their idea to begin with. Boggles my mind - I recall them telling me how stupid my idea was, only to see them come up with almost the same idea themselves shortly thereafter. I won’t give specific examples because I don’t feel like re-fighting those old wars. They should know who they are…but they probably don’t. They really think that my idea was stupid but then they came up with a “different” idea that was great.
You can’t win so don’t even try. Be creative, do your best, and don’t worry about the credit so much. But do what I did - put all your best ideas out there via AIAA papers and such, so you can later prove that you did it.
And don’t expect to get rich by selling aircraft design concepts - it just doesn’t work that way.
October 19th, 2010 at 5:20 am
Thanks for the advice it is much appreciated as the problems I have been having have been really eating away at me. It leaves us with a feeling of should we or shouldn’t we share our ideas.
In my case, somebody was claiming that my designs, which were built, were their work all along. I have found that nobody wants to be anywhere near a project that is on the verge of being a failure and they certainly don’t want to help out. But after you have put the long hours in to turn it around and it is starting to be sucessful again, everybody quickly comes out of the woodwork and are all too eager to push you out of the way. I guess that this is a situation that is all too familiar to yourself also.
I watched a documentary about the Wright brothers a short while ago, and their father (the vicar), always kept telling them to be very carefull who they trust. Very wise words I think.
I have quickly learnt that I am never going to get rich designing aircraft and some weeks it is a struggle just to put food on the table. All this is while my neighbours with manual factory jobs are living what seems like a life of luxury in comparison. Despite this, I am never going to stop designing aircraft because it is who I am and what I love doing. You could also say it is in my blood since my great uncle was one of the designers on both the space and missile programmes at Woomera in Australia.
It has been really nice talking to you and the opportunity to be able listen to the perspectives of engineer at the top of his career. Thankyou
October 19th, 2010 at 8:39 am
If you have a degree in aeronautical engineering, get a job in that field - whatever you can even if it isn’t new aircraft concept work. If you don’t have such a degree, try to get one. If you can’t do the engineering calculations to prove out your ideas, they are just ideas and nobody else is going to put in the work to prove them out. Other people have their own ideas to prove out.
Best of luck to you, and all others out there like you.
October 19th, 2010 at 1:49 pm
I have got the all the qualifications I can think of, which consist of,
- PhD in aircraft conceptual design - incorporating advanced technologies
- Masters degree in aircraft design
- Batchelors degree in mechanical engineering
- Plus certificates in computer aided design as well as some practical trades
- Some industrial design experience on an industry based aerospace research project as well as some experience as a design draghtsman
- I also have a number of years of practical work experience straightening severely impacted cars
It is just a case of trying to find a company willing to give me a chance now. This is proving to be the really hard part as companies only seem to want people with 10+ years industry experience. I am willing to work for the same as a unskilled factory operative for the right opportunity, but companies still are not interested. Maybee it is my age, 36.
I will never stop designing aircraft, even if it just for myself.
October 20th, 2010 at 6:16 am
Renzo: While calculating the take off gross weight for a jet transport using the methods prescribed by the book, Aircraft design a conceptual approach my total mission weight fraction was calculated as 0.487. This value when transferred to fuel fraction gave 0.544.
The empty weight fraction is 0.486 (and higher than that). The problem when calculating take off gross weight is that i get the takeoff weight values in negative numbers as
(crew + payload)/(1-0.554-0.486) the denominator is negative
can someone please help me
My all mission segment weight fractions are 0.9 something, except range segment which is 0.518
i am using range = 18520 km, c=0.0001389 1/s, v=250.792 m/s, L/D=15.588
I have checked it more than 20 times its still the same. Also used Roskam method but still the same (more weird results) i think there must be something wrong with the specification probably range too large which yields less range segment fraction.
can anyone please help me or any suggestions ???
October 20th, 2010 at 7:47 am
Two things to look at:
1) The method may be telling you that with the technology and design you are studying, it is not possible to get 18,520 km of range (exactly 10,000 nmi). Not too many airplanes go that far.
2) You are using metric for range and speed but your C value appears to be in British Imperial units, exactly equaling 0.5 1/hr. Perhaps you don’t realize that C is NOT non-dimensional, and that the units of 1/hr is a shorthand notation for lb/hr/lb in which the first lb is MASS whereas the second is FORCE. Cancelling lb with lb to get 1/hr is an old inside joke, not a legitimate operation. This is explained in my book.
In metric, your value of 0.5 1/hr is properly 14.16 mg/Ns.
October 20th, 2010 at 9:28 am
Thanks for the suggestion and information, Dr Raymer.
In fact, While solving the problem for the first time, i tried using 14.6 mg/Ns for c but that would give me a very large value e^-66796.855 which is equal to zero.
we convert C unit from 1/hr to 1/s for calculation in imperial do we have to convert mg/Ns to something simpler. Is mg is milligram and needs to be changed to kilogram If not then perhaps you are right.
I was also thinking, as i am using simple cruise mission profile (takeoff, climb, cruise, loiter, land), is this affecting my calculations (i.e. results coming in negative).
October 20th, 2010 at 10:05 am
Yes, you must make sure that all the units are consistent. mg is Milligrams and must be converted to grams. Km must be converted to meters. Etc…
Also don’t forget the minus sign out front.
October 21st, 2010 at 8:30 am
Hello, Dr Raymer i finally solved the problem but again my calculated takeoff gross weight is 85,774 kgs for a range of 18520 Km carrying 350 passengers. i think this would make the aircraft pretty light, isn’t it for that sort of category??? i have checked it and every thing is fine……i would be more than grateful if you could proof read my work.. it is only 2 page long with specification and neat calculations…
October 21st, 2010 at 8:45 am
I am terribly sorry but I simply cannot take the time to double-check the calculations of everyone who asks. I hope you understand. Those methods work, and if you are getting crazy answers then either the requirements are unrealistic, there is some unrealistic input number, or the actual calculations are being done incorrectly. I’ve already cautioned about the use of “g” in metric calculations (9.8), and cautioned about making sure that the units are consistent. Are you using the metric version of the empty weight ratio statistical equation?
October 21st, 2010 at 8:57 am
Yes, i am using the metric version i.e. for jet transport 0.97W0^-.06
I also converted Ccruise from 14.16 mg/Ns to 0.00001416 Kg/Ns and same for loiter 0.0000113 Kg/Ns, if i convert it to gram then it would give me zero
i am also aware about the g = 9.81 m/s^2 but i don’t think we need it during sizing calculation.
October 27th, 2010 at 6:20 pm
Hello Dr. Raymer.
I know this is the third time I’ve posted on your blog, so I hope I haven’t become a nuissance. This time, I only have one question: Is there any recommended minimum distance to space two vertical tails apart from each other to minimize interference drag? For example, the vertical tails on the T-10 prototype look to be unusually close together. On the production Su-27, it looks like they have been more widely spaced (being outboard of the engines instead of on top of them). My hypothesis is that putting extra space between the tails reduced interference drag, but I’m not sure.
October 29th, 2010 at 10:19 pm
I think it would be good to have a search function for your website. A search bar on the home page would be nice.
October 30th, 2010 at 6:22 pm
Lance - I haven’t seen any serious study of this - we all just use our best judgement then go into CFD and wind tunnel. I’d like to keep the tails more than half their height away from each other, and at least double their mean chord away from each other. Canting them outwards helps with interference but can cause weird pitching moments. Look at the F-15, F-14, and F-18 to calibrate your eyeball.
Patrick - Great idea. I wonder how that is done. I’ll check with my service provider to see if they have an easy routine call that I can paste into my HTML.
November 3rd, 2010 at 7:20 pm
I was waiting to get on a flight from LA to Miami last week. There was an older gray-haired man standing with his back to me, and his old-but-glamourous wife, whom my wife noticed because her outfit was stylishly quirky, like something my wife would wear. This woman was chatting up a storm to her mostly-quiet husband. At one point she lovingly called him “Buzz” and my wife, who is Swedish, was puzzled. She’d never heard such a name and asked me in a whisper if that was a real name here in America.
“Sure,” I said, “it is sometimes used as a nickname for “Bastian.” “The guy who ran Rockwell North American when I started working there was named Buzz.” “Thinking some more I said, “I guess the most famous `Buzz’ is the astronaut Buzz Aldrin - second man to walk on the moon. But I don’t remember if his first name is Bastian or if he got the nickname some other way.”
A few minutes later we heard her call him “Buzz Aldrin.” I looked more closely at her and noticed that she had some sort of dangling necklace with the famous on-the-moon photo of Aldrin. No way. Yes, it really was Buzz Aldrin.
After a few minutes, when he’d turned towards me to walk past, I stuck out my hand and told him I was an aircraft designer and asked if he’d mind if I shook his hand. He did, then walked away.
Another passenger, standing next to us, noticed that I’d shaken Aldrin’s hand and asked me, “Hey, was that Johnny Carson?”
As we were all getting off the flight hours later I happened to walk past Aldrin again and told him what the other guy had asked me. He chuckled and said he hadn’t seen Carson in years.
November 12th, 2010 at 5:23 pm
Hi
I love it when you just never know who you are really sitting next to in cafe etc. It might just be me, but I have learnt over the years that the people who wear the smartest suits are the ones who sometime know the least. The top guys are those who blend into the crowd.
I live near Derby in the UK and only learnt recently that the birth place of Sir Barnes Wallis is just down the road from me. The amount of times I have walked past that house and never noticed it.
I was looking at a picture of the Galileo Avionica “Falco” UAV the other day. The intersting thing about the twin boom design is that the vertical tails are canted inwards very slightly. I am sure that there must be a reason for it, possibly an aerodynamic feature with respect to the wing shape. I would love to hear your thoughts.
Ady
November 24th, 2010 at 3:58 am
In your book at the back of the engine performance curve it says partial throttle at 36 k does that mean partial throttle setting at 36000 ft
November 28th, 2010 at 6:21 pm
Adrian: Angled-in vertical tails can be for a million reasons. Prime suspect - it was found that rudder deflection caused a pitching moment for some reason, and this fixed it. But there are soooooooo many other possibilities, like a weird flutter or accoustical resonance between the two sides, or ease of fabrication, or easier linkages, or ….
Ud: 36k is 36,000 feet.
November 29th, 2010 at 6:01 am
Thanks for clearing that up. It was more than likely a preliminary design fix rather than a conceptual design choice. It can be very difficult to look at a design and then try and get into the mind of the designer expecially when designs evolve so much later on down the line. I once spotted the back of the envelope sketches for concorde in a magazine which were very interesting.
November 30th, 2010 at 7:24 am
A friend of mine told me, using drooped wings for a ucav provides better manoeuvrability compared to tailless flying design and does not necessarily demand thrust vectoring. This configuration is also stealthier compared to angled vertical tails. Is this true??
November 30th, 2010 at 9:18 am
I’m not sure what he means by “drooped wings.” Negative dihedral, like the C-5 and Harrier? Downward-angled wingtips? Also, what sort of maneuverability is supposed to be better - turn rate, sustained turn, agility,…?
Sorry, I’m not trying to duck the question. I just don’t understand what your friend meant.
December 1st, 2010 at 1:15 pm
Hello Mr. Raymer.
I am currently an undergrad student in electrical engineering but my passion for flying planes cannot be defined through words. So i made up my mind to build a manned glider first. I bought your Aircraft Design: A Conceptual Approach, it is a really cool and awesome book, but the stuff to glider planes is quite limited. Could you propose some good design books on gliders?
Have a nice day.
December 2nd, 2010 at 7:08 am
Hello Dr. Raymer,
Is the initial sizing method mentioned on your book (aircraftdesign: A conceptual approach) applicable to BWB design such as x-45 as BWB is lighter than the conventional design. Also, can we use the data for fighters instead of bombers for such type of aircraft as the bombers tend to be very heavy.
December 2nd, 2010 at 7:59 am
Zahid - A good one is Fundamentals of Sailplane Design by Fred Thomas and Judah Milgram (1999). It’s on Amazon.
Renzo - The sizing methods apply to BWB. For a usable empty weight equation, read the literature about BWB’s to find one or more credible empty weight estimates (along with Wo) and use it to adjust the Transport/Bomber statistical equation (Chapter 3).
December 4th, 2010 at 1:25 pm
Thanks Dr Raymer,
When one uses trapezoidal wing is trailing edge sweep important. i am trying to design a tailless unmanned combat aerial vehicle using such wings and engines placed at the top like that of x 45
December 4th, 2010 at 2:46 pm
I also developed a specification
Is this specification unrealistic………..
MISSION SPECIFICATION FOR A UCAV
Payload: 4500 lbs [2 x 1000 pound JDAMS (GBU 31) and 2 x AIM-120s]
Crew: None
Range: 1200 nm (Combat radius) followed by 7 hour loiter
Altitude: 40,000 ft for the design range
Cruise speed: Mach 0.85
Fuel type: JP8
Power plant: Single non afterburning turbofan engine.
PERFORMANCE REQUIREMENTS
Take-off and landing: 1000 ft ground roll
Approach speed 130 kts
Maximum speed Mach 1.6 in 30 sec at 20,000 ft
20 deg/sec turn rate at 350 kts at 15,000 ft
dash in/out 100nm
combat will include one 180 deg turn and 360 deg turn at 15000 ft
And i am planning to use high bypass ratio turbofan engine provided in your book
December 4th, 2010 at 3:08 pm
Renzo - the trailing edge is usually defined from the other parameters, namely aspect ratio, taper ratio, and sweep of leading edge or sometimes, quarter chord line. It is important to avoid excessive trailing edge sweep as it makes the flaps work poorly (or elevators for a tailless airplane). For hypersonic aircraft like the Space Shuttle, it is better for stability to have a slightly negative trailing edge sweep in any case.
I just can’t comment on any specific project. I do this for a living!
December 6th, 2010 at 10:26 am
Thank you…. Is that the reason why aircrafts like f-22 use inverse sweep at the back inorfer to improve control effectiveness.
December 6th, 2010 at 10:56 am
For hypersonic aircraft, that negative trailing edge sweep is more for pitch stability than control effectiveness. On the F-22 it probably has more to do with the usual compromise between aerodynamic effectiveness (higher aspect ratio) and structural weight (lower aspect ratio). The actual sweep angle was probably set by stealth requirements, with these other factors considered as well. Note that Lockheed’s original proposal had positive sweep at the trailing edge - design trade studies undoubtedly showed that the current negative sweep gave a better airplane all around.
Aircraft design is complicated, folks!
December 11th, 2010 at 9:10 am
A question for readers: When writing my new book, Living in the Future, I amused myself by sticking in a number of cultural and historical references, some obvious, some hidden. A few can be seen in the Table of Contents (http://www.aircraftdesign.com/livingfuture-toc.pdf) such as the advertising phrase “But Wait - There’s More!” in the title of Chapter 18, or the two song titles mashed into “Total Eclipse of the Dark Side of the Moon” as a subsection title in Chapter 9.
Silly stuff. I had fun.
Would anybody be interested if I gathered and posted a complete list with a “decode” note for each? Or is it more fun to find them yourselves? Or doesn’t anybody care? Or is it more like, “what new book?”
Holiday Cheers to One and All!
December 15th, 2010 at 6:35 pm
Hi Dan
It might be good to see a few decode notes. Some people in other parts of the world might have such different cultural backgrounds that it might leave them confused. For example, I bet some of you guys on the other side of the pond haven’t even heard of Iron Maiden (the best english band, not suitable for migraine sufferers though!)
Writing humour is such a difficult task, I have unfortunatly lost a couple of good friends who have taken my humourous e-mails the wrong way. It is all too easy for things to unfortunatly be read in a different way to which they were written.
A couple of the guys over here at Cranfield, told me that you visited us and gave a good talk a few years back. It was a shame it was before I started at Cranfield.
Have a good christmas.
December 16th, 2010 at 1:43 am
Iron Maiden - of course we other-side-of-pond-ers have heard of them! And, that is a great example of the use of cultural references for humor that people not from America or the UK might not get. Remember the reference in “Bill & Ted’s Excellent Adventure?” Hilarious, but only if you realize that “iron maiden” is both a rock band and a torture instrument in Medieval England.
But “…the best English band..”? Beatles, Queen, Bowie, Stones,…. ever heard of those guys?
Now I’ve done it. Started a non-aircraft-design inter-generational flame war on my previously-pristine site. OK, take your best shot, then let’s call a truce!
December 16th, 2010 at 2:00 am
Concerning my Cranfield visit - page 139 in the new book. Great place, wonderful people.
Not in the book - that was the only time I’ve ever been late for a lecture. The on-campus guest house didn’t have an alarm clock in the room and there wasn’t a front desk for a wakeup call, so all I had to pry me from my jetlag-induced slumber was my tiny digital watch. It didn’t work. When I failed to show up for my early-morning lecture, one of the professors came to the guest house and pounded on my door. As I groggily apologized he said “no problem” and that he’d told the students to work on their projects, but I think he was rightfully displeased.
The slightly-late lecture went fine, but I still feel bad about it.
December 16th, 2010 at 4:12 am
I will deffinatly agree with you on the beetles, since those guys were the inspiration for many of the bands that have followed since. We are however missing Def Leppard from that list. There is a place called Sheffield not far from where I live, where Def Leppard formed and where Bruce Dickinson grew up. The new liverpool maybe! How many bands have got their own plane like iron maidens ed-force one. Have you seen the TV series ‘flying heavy metal’ by Bruce?, very entertaining. I can also confirm that there new album is a good one.
I had heard in passing about the incident at Cranfield but didn’t know if it was true, did a couple of beers at the student union play a part in it as well ? It would have been Mitchell Hall that you stayed in on campus. I know the professor and he is a nice guy and pretty relaxed. I wouldn’t worry about it, some of the staff do a lot worse themselves. I heard that the students learnt some good stuff so mission accomplished. If i’m ever in the US, I wouldn’t mind coming along to one of your courses myself.
December 16th, 2010 at 1:39 pm
Wow - that story is still being told, a decade later??!!
Yes, there were beers involved the night before - some students took me to the pub to expose me to typical UK culture. But, it wasn’t too many and that’s never made me late before.
I’d assign the blame as 85% jet lag, 15% pub-crawl, and 100% Raymer….
I’m teaching my classes in Los Angeles this Feb. - come on over, warm up a bit!
December 16th, 2010 at 5:10 pm
I would love to come on over but my finances are holding me back as I am in the last weeks of my PhD and I am now seriously broke as a result. The joys of being a student, seriously long work hours followed by bread and jam for dinner.
December 18th, 2010 at 11:14 am
Dr. Raymer,
I bought your book and i learnt more than i can digest in one sitting. The conceptual design book will be combed through many times to extract every bit of information from it. Thanks!!
I hope to save up enough to attend your 5 day session on it at LA.
Happy holidays!
December 20th, 2010 at 3:22 pm
By the way, i am curious as to when you flew the HAL Tejas. The twin seater has its first flight a couple of years ago (?). I believe HAL is close to getting full operational clearance by mid 2011. and deliveries to start soonafter. Were you involved with the development of that fighter?
December 20th, 2010 at 3:33 pm
Look more carefully at my bio - I flew the simulator! But I’d love to get a ride in the real thing.
No, I wasn’t involved in the development but I did get to see a bit during my visit there. Nice composites work.
The simulator flew great. Nice plane - I wish it a long production run and a useful operational life. All India should be proud.
December 21st, 2010 at 9:26 am
I am interested to procure your lecture notes at a price as I cannot attend the lecture classes. How to get it and at what cost?
December 21st, 2010 at 10:03 am
Hello,
Unfortunately I cannot sell the lecture notes. Certain materials such as airplane photos and component illustrations are used via the “Fair Use” educational criteria in the US copyright law. I can only pass it out to my students, not sell it, even just to cover the printing costs.
Instead, buy my textbook, which has all the important technical material.
December 22nd, 2010 at 6:48 am
Dr Raymer, we are currently designing a ground attack fighter for undergraduate university group design class project. Our specification calls for 4500 lbs of payload. we are planning to use 2×2000 lbs of JDAMs. I think it will be about 2200 lbs each when installed on the aircraft but the problem is no matter what we could not find any dimensions for this sort of bomb. We even looked into aviation week source book 2009 with no luck…Do you know where can i find it or can you just give us a rough guess? We need this information to size our internal bomb bay.
December 22nd, 2010 at 10:44 am
Guys - it took me 2 minutes to find it at
http://en.wikipedia.org/wiki/Mark_84_bomb
And I’m the old guy……
Have fun with your project!
December 23rd, 2010 at 8:47 am
How important is area rule in fighter aircraft design? Is it possible to achieve practically without compromise? Are exisitng fighter aircrafts fully meet this rule?
December 27th, 2010 at 3:10 pm
Merry Christmas and a Happy New Year to you all !!
January 6th, 2011 at 11:25 am
Dr. Raymer,
just on a side note your book is like the holy grail of aerospace engineering! I am a junior at the UofM in AE, and being an international student it is very difficult(espcially now) to get into the aerospace filed let alone the military. I know I don’t stand a chance with military aircraft companies such as Lockheed, so might I say I don’t mind sticking to commercial aircrafts. This is what I love to do so anything with airplanes works for me, do you know of any companies around the U.S where you can work and not be a U.S citizen/person ? Maybe just have a work visa ? Thank you for your time I’m just trying to find and see if there’s any hope for me to work in this field! :)
January 8th, 2011 at 10:50 am
Jhon - I found that information on the internet very quickly - and I’m old!
Akspas - The area rule reduces drag right around Mach One. At higher speeds we use more complicated methods, mostly computer programs, to minimize supersonic wave drag. However, we are always compromising with other things such as structural weight and manufacturing simplicity.
Kareem - These days even organizations like Boeing Commercial have problems hiring non-US folks, due to ITAR and other restrictions on even non-military technologies. If I were you I’d try the new small companies doing general aviation designs. There is “hope” since every year, some foreigners manage to find a way to stay and work in our aerospace industry, but it isn’t easy and it seems to get harder every year.
January 10th, 2011 at 5:58 am
sir do you have some tips for me
i want to study BSAE (bachelor of science in Aeronautical Engineering)
and i wanted to be successful will you please reply on my email?
and can we be friends?
im 15yr old dreamer to be a great man in the future…
^^
January 10th, 2011 at 8:47 am
Alfert - Nice to hear from someone who is just like me, many years ago. I was thinking of teenagers like you when I wrote the advice at http://www.aircraftdesign.com/ray-rule-wouldbe.html . It’s the best advice I can give. Good luck!
January 12th, 2011 at 10:08 am
Dr. Raymer,
I just have a quick question. So in a case of an extreme high angle of attack, the tails are going to get blanketed correct ? Does it matter what type of configuration you have ? I mean would you have more advantage having a V-tail for example versus a conventional tail layout ?
Thanks again for your time!
January 12th, 2011 at 3:58 pm
Kareem - at extreme AOA the tails often get blanketed. The tail geometry does make a difference - a horizontal tail lower than the wing is better, and a ventral (bottom) vertical tail is lots better if you can make it fit. A V-tail may be better, or maybe not. As to vertical tail, there is no firm rule. You have to have a designer who can almost “see” the air, then run some CFD, and then take it to a good wind tunnel.
January 14th, 2011 at 4:07 pm
Dan Raymer,
How can I calculate the mean aerodynamic chord of a elliptical wing?
If I use the formula in the figure 4.17(I have the fourth edition), I will obtain 2/3 of the chord, is this the mac of elliptical wings or there are another way to find it?
Thanks
January 14th, 2011 at 4:54 pm
Other sources say “The MAC of an elliptical wing is 85% of the root chord and is located at 42.4% of the half wingspan from the root chord.” I haven’t used one myself so the subject never came up.
January 18th, 2011 at 6:51 am
Hi!
I´m interested in scale model testing. And I want to know what is the best or the most accurate scale for an aircraft scale model. Especially in aerodynamic testing. And if that scale is not used normally because of practicality reasons I´m interested what is used most often by companys…??? Thanks Dan!
January 18th, 2011 at 7:16 am
For scale testing, bigger is almost always better. There is no “standard” or
“best” size, other than full scale. If it is a free flight model, the weight and
mass distributions have to be scaled properly to get proper dynamic motion for stability and control. These scaling factors are described in this NASA report:
http://www.aeronautics.nasa.gov/ebooks/downloads/ModelingFlight.pdf
You also have to worry about Reynold’s Number effects on the
aerodynamics.
In general, I don’t think it is a good idea when people fly a little RC model of their homebuilt airplane design, then build the real one thinking it will fly the same. You have to really know what you are doing to get usable results.
January 20th, 2011 at 9:38 am
I’ve got through to P.19 of ‘Simplified’. Unfortunately my fuel fraction comes out as 1.0. With range 500 miles, -R = -2640000 feet. With that figure, ‘e’ hasn’t a chance of becoming anything other than zero. I must be doing something wrong.
January 20th, 2011 at 9:52 am
Make sure that ALL the numbers are converted to consistent units. People often forget to convert engine specific fuel consumption from using hours to using seconds - divide by 3600. Otherwise, just double-check everything again. The method works, I promise!
January 20th, 2011 at 12:53 pm
Hello Dr Raymer,
Recently, I came across a book called Civil jet aircraft design written by Jenkinson, simpkin and Rhodes (1999). It suggests its own method of calculating takeoff weight. An example has been shown by the authors on pg 132. I am surprised by the fact that these authors are directly using payload in Kg, sfc in lb/hr/lb, speed in knots and their final answer is in Kg. This doesnt make any sense, If you have the time, check it out. If i am correct than thisf books is just giving false information to the students.
January 20th, 2011 at 1:37 pm
You can redo the equation to use any units you wish. I only have a preprint review copy of that book so I don’t know which page you are on, but if you are correct I can only say that the authors thought that those were reasonable and convenient units.
In Europe they are forced to use such mish-mashes, using metric where they can but using old British units like knots and nautical miles where the pilots and the air traffic controllers stick with the classical units.
In my book I deliberately keep all such equations unitless, meaning that you the reader must make sure that all units are consistent. So, if you are using fps for speed, you must use feet for range, etc… This is “cleaner” I think, and avoids the use of some magical constant out in front of the equation.
Even then, the use of “pounds” for both force and mass in everyday British units leads to trouble when applying equations to metric values. You must insert 9.8 in the right place…see the introductory note in the front of my textbook (4th edition).
January 24th, 2011 at 6:15 am
Thanks, Dr. Raymer. I now get fuel fraction 0.12, which looks OK. I’ll try to avoid asking kindergarten questions in future. G. Fyfe
February 1st, 2011 at 3:08 am
Dear Dr. Raymer.
I was wondering about if you can help me finding some literature about helicopter or rotorcraft desing more acurracy systems. Thanks very much in advance for your attencion and help.
Andr Roll.
February 1st, 2011 at 7:01 am
The books on helicopter design that I find useful are the ones by Prouty and Johnson - see http://www.aircraftdesign.com/books.html#Tip2 . My Aircraft Design textbook has a large subchapter on the subject as well.
February 2nd, 2011 at 6:14 am
Hello dr raymer,
i was going through the light weight fighter example in your 4th edition book. While calculating the landing wing loading you have used equation 5.11. In that eqn there is a parameter shown by lower case greek symbol sigma.
I know that parameter is a density ratio = density at that altitude/sea level altitude but how do we calculate the density at takeoff and landing. The example doesnt state take-off and landing altitudes. I am also keen to know which altitudes did you use for take off and landing? Thanking you in anticipation.
February 2nd, 2011 at 8:36 am
That is AIR density, which can be found in the Appendices or in many places online. It is common to do the calculation at sea level so the density ratio is 1.0, or to assume a hot day at 5,000 ft (Denver in the summer) which gives a ratio of 0.8 (0.794 actually). This was all discussed a few pages before equation 5.11 used the ratio.
February 2nd, 2011 at 8:48 am
Thankyou sir, you are the best!!!!!!!!!!
February 3rd, 2011 at 4:14 am
Thank you sir for this Website……It helped me alot to figure out my way to be an aeronautical engineer
February 9th, 2011 at 1:16 pm
I am using the fourth edition of your book and while going through the fighter aircraft example i noticed that you multiplied 3.8 times the mass flow rate but when you look at fig 10.16 shouldn’t it be around 0.027. Thankyou
February 9th, 2011 at 1:24 pm
sorry, for the trouble i figured it out myself.
i think its
12 in = 1 ft
144 in^2 = 1 ft^2
0.0268 = 3.859
Thanks but again i have a question in the rds propulsion module do we enter the actual area or the ratio i.e. 3.8 for Acapture
February 11th, 2011 at 11:51 am
A gentle reminder to my guests: As it says above…
Please don’t post links to other websites here !
I’ve deleted the link recently posted
February 11th, 2011 at 5:21 pm
Acapture is actual capture area in sqft or sqm
February 13th, 2011 at 9:35 am
Thanks dr raymer,
I am designing a ucav which can carry 2 * 2000 lbs of bomb after doing all the calculations. i just realised my bombs are longer than my engine. While i was designing the engine in the dlm module the engine looks relatively smaller than the payload. Is this normal? I think it might be because i used the t/w as 0.6 (very small but reasonable for ucavs).
February 13th, 2011 at 1:15 pm
Dr Raymer, can rds student dlm files be exported into rhinoceros which is a NURBS modelling software or any other cad packages…
February 15th, 2011 at 6:24 pm
Hi
I have an interesting question with regards laying out a design. In industry, do you normally take the root airfoil as being at the fuselage side or the wing centreline. It gets more complicated when we think about flying wings with a blended fuselage.
If we also think about a vertical tail with a large blend at the leading edge of its base (to blend it in with the fuselage), where do we take the root airfoil as being now.
Can you also recommend any good references on rocket and spacecraft design. My great uncle was a designer of the black arrow and I am getting the urge to expand my knowledge and try and follow in his footsteps.
Thanks
February 19th, 2011 at 9:59 am
Roy: RDS-Professional can export a RHINO script for direct import, including options for smoothing. RDS-Student does not have this.
Ady: For aerodynamic and stability analysis the “root” of a wing is at the centerline of the aircraft, projected from the wing’s leading and trailing edges. For structural design and when pilots talk, the “root” is at the side of the fuselage. If a wing is highly blended or curved, sometimes the “root” is just a figment of someone’s imagination. In the end, the air figures it out.
I have a chapter in my textbook on spacecraft and rocket design. It should get you started
February 19th, 2011 at 5:10 pm
Roy (your earlier post): It sounds a little odd for the bombs to be longer than the engine, but there is no direct connection between their lengths! Doublecheck all calculations……
February 19th, 2011 at 5:38 pm
My question is more focused towards the lofting of a vertical tail. If we think about the vertical tail on the B-29 for example. At some point along the span of the tail surface, we have to split the surface between the basic lifting surface and the surface that blends this to the rest of the aircraft.
If using a CAD program, is it practice to cut the surface off at 75% of its soan and then fabricate a blend for the rest ?
It apprears that by the time we have finished lofting such a surface, any original airfoil profile has long gone.
February 28th, 2011 at 3:29 pm
Hi Dan,
I recently purchased the RDS student package to aid my current masters project. Unfortunately on install it is telling me, software not supported on this system. It suggests it could be because I require the correct version of windows, 32bit or 64bit. I currently use windows 7. Apologies for being a pain, any advice?
Regards,
Alex
February 28th, 2011 at 5:30 pm
If RDS will not run on your version of Windows, see www.aircraftdesign.com/rdstips.html#Tip3
March 7th, 2011 at 10:55 am
Dr. Raymer,
I was wondering if you knew of any books out there ( probably old) that teach you how to loft, specifically tailored to Aircraft design ? I know there’s CAD programs out there but it’s always fun to learn the old school way using a pencil and a paper.
Thanks you for your time.
Kareem
March 9th, 2011 at 7:07 am
Dear Dr Raymer.
I have one question to you. I was wondering if the RDS software are allowed to analize a tilt rotor aircraft?
Or if you fave some information about, how to calculate the tilt rotor performance?
I appreciate you help.
Kind Regards]
Carlos
March 11th, 2011 at 10:34 am
Kareem: My textbook has a lot on lofting, and an introduction is in my homebuilders book. An old book by Roy Liming is the definitive work but is hard to find. It isn’t on Amazon - maybe eBay? The title is “Practical Analytical Geometry with Applications to Aircraft” (1945).
Carlos: RDS can handle the analysis of a tilt rotor aircraft in forward flight mode. The RDS static propeller thrust calculation will probably be approximately correct for an initial analysis of hover thrust. A good value for hovering power and control would take a dedicated helicopter code.
March 14th, 2011 at 4:48 pm
Once again I am getting postings from jerks trying to sell something. I immediately delete them.
If you are a human, please stop it. If you are not human please follow the Fourth Law of Robotics - “A Robot shall not Spam nor through Inaction, allow other robots to Spam.”
Like that? I just made it up, with apologies to the great Asimov.
If it gets to be too much of a problem I’ll have to stick in one of those twisted letter thingys, and I hate them myself.
March 17th, 2011 at 9:55 am
Dr raymer,
How do we calculate the l/d ratio for climb. My aeroplane has max l/d around 23 so how do i calculate the l/d for climb. i need it to calculate the t/w for climb but couldn’t find it in your book.
March 17th, 2011 at 10:07 am
Also in your 3rd edition book pg 871 the minimun climb gradient is expressed in % do we have to divide the numbers by 100. Also, do we have to add first, 2nd and 3rd climb gradient inorder to get the total climb gradient?
March 31st, 2011 at 1:55 am
Dear Dr Raymer, Is there an obvious reason as to why the spanwise distance of the mean aerodynamic chord (MAC) of the fin from the fuselage reference line is twice the value calculated from the standard formula? And will the length of the MAC be the local chord length (smaller) at this station for a tapered fin? Thank you.
April 4th, 2011 at 11:03 am
Hello, Dr. Raymer
I have question about carpet plotting.
When we assume a pair of (T/Wto,Wto/S), how we calculate Wto with this pair?
and with this new Wto our main (T/Wto,Wto/S) will chage, should we use this new pair for plotting the carpet?
Could we take a fix thrust and still have a perfect plot?
I will look for your helpful guidelines.
Thank you for assistance.
April 5th, 2011 at 3:40 am
Hello Sir
Is there any relation to determine the weight at each point in a wing.I am asking this so tat i can estimate the total load(lift at d same as been found) on the wing at each point.Awaiting for reply
April 7th, 2011 at 7:27 am
How important or significant is the bow tail angle in shaping an military aircraft especially in the rear portion of the fuselage. How this angle is related to the performance of the aircraft.
April 9th, 2011 at 8:57 am
Simplified p.23, Tip Speed. What is V?
April 13th, 2011 at 4:35 am
Hello.
I ever think that airplanes were a wonderful objects.
What do you think about materials to build models that have
a higher g.
Thank you for the eventually interest.
Bye
April 19th, 2011 at 1:55 pm
Dr. Raymer, I have two of your “Fourth Edition” books. I bought one, then when taking your short class, got the other as part of the course material. The first is a pathetic mess of post its and highlights, the second is spanking new. Is it o.k. for me to sell the second one? I want to do what is ethically proper here and to not cut into your sales. I don’t want to chuck it in the garbage either.
April 20th, 2011 at 3:28 am
Dear Sir
Can you recommend any really good books on structural design which would have been used by people prior to the 1970’s. We still have some excellent aircraft flying around from these early days which were designed at a time long before the development of FEA and I am interested in going back to the roots.
Thanks
April 20th, 2011 at 6:36 am
I am not Dr Raymer, but analysis and design of flight vehicle structures by E.F. Bruhn is a pretty old book which is considered as holy grail by structural engineers……..Aircraft structures books written by THG Megson are also pretty good…..
April 20th, 2011 at 11:05 am
While back I purchased your book “Simplified Aircraft Design for Homebuilders” I never got the free software for it, I was moving at the time and forgot about it. I have gone on to your site looking for it (the spread sheet) so where is it located at? and the cost so I can order myself a copy of it. Thank you.
April 30th, 2011 at 9:29 am
Dear Sir
A couple of quick questions. Do you know of any good weight prediction methods for sailplane wings. These seem to be outside the boundaries of traditional optimisation methods of and I have had to apply an additional structural strength parameter which has constrained the aspect ratio to that of simular designs.
I assume that the initial estimates that you use for wing dihedral are for the aircraft on the ground ? In the case of high aspect ratio wings, the wings can bend significantly in flight and change the dihedral. Is there some additional dihedral allowance that needs to be incorporated for this effect ? I guess in industry it involves a lot of data being passed back and forth between the aerodynamics and structures teams.
Have you thought about writing a whole book of various design examples to suppliment your text book ? It would be good to see how yourself would put theory into practice. This seems to be the problem with a lot of education courses, they can give you the theory but the practical experience is something else.
Thanks
Adrian
May 6th, 2011 at 9:01 am
Simplified p.23, Tip Speed. Can anyone tell me what V is? It doesn’t have to be the good Dr., any one of you bright lads and lasses can lighten my darkness.
May 8th, 2011 at 3:49 pm
Graham, this is not Dr Raymer. I don’t have a copy of the book to hand but if you could tell me what the equation is for or try and write the equation out I will try and help if I can. I can only assume that you are talking about propellor tip speed in which case it would be a function of the engine RPM and the propellor diameter. Both of which are design variables. Google angular velocity, v=w.r
Hope this helps
May 14th, 2011 at 3:41 am
Dr. Raymer
One thing I do miss in Simplified ….. is wing tips.
I could not find anything on the web on how to design a hoerner tip.
Where can I get the parameters for that?
I would love to atten a workshop but 16 000 kilometers is a bit far (South Afrika). Your book is a great help!
Thanks
Manie.
June 13th, 2011 at 2:59 am
Everyone, as it has been 3 months since Dr. Raymer last replied to any of us we have to assume that he is really busy launching his new book. I have come up with an idea though, I am thinking about starting up a yahoo group which will be a place where we can share thoughts and experiences in aircraft design and try and help each other out. Would anybody else be interested ?
June 13th, 2011 at 8:16 am
Oh - you know how to hurt a guy! Sorry I haven’t replied in a while. Yes, I’ve been crazy busy, but on programming, not the next book.
I’ll get to some answers pretty soon - and maybe I’ll set up a separate thread on this site for peer-to-peer pratter.
Cheers, all!
June 14th, 2011 at 5:48 am
Tht yahoo group idea would be a good idea
June 16th, 2011 at 1:48 am
Sorry Dr Raymer, didn’t mean to offend. I just though it would be a good idea to take a bit of work off of your shoulders as some of the low level questions could be answered by fellow students. I can imagine it probably gets frustrating when you are really busy with other things.
A discussion forum would be a great idea. Maybee you could appoint one or two people to act as your disciples and moderators. In the mean time, if it is ok with Dr. Raymer, I would like to try and help out and answer a few questions if I can?
June 25th, 2011 at 3:18 pm
Dr. Raymer,
I love aviation and have always wanted to design my own plane. I am very interested in reading your books but have been holding off buying simplified aircraft design in the hopes that you will come out with an ebook version on amazon. I find it much easier to take, and later search notes and important sections. It makes a book so much more valuable as a reference.
Do you have any plans on releasing your books in an ebook format?
Thanks!
June 29th, 2011 at 7:57 am
Hello Daniel
I’m a french engineer, I’ve read your Fourth edition of Conceptual Approach of Aircraft Design. Very interresting! Nevertheless I’ve a question concerning induced drag calculation in subsonic phase, describe pages 349-350. In fact, I’m calculating aerodynamic derivatives based on Doublet Lattice Method in stationnary domain (Equivalent to VLM). My aircraft shape is modeled by flat planes. Calculations have provided a aerodynamic span load. Now, I would like to calculate induced drag. According to your comments the induced drag is N (normal force to the flat plane) time the sinus of the angle of attack. Finally we obtain the induced drag in case of 0% suction effect as Cdi = Cl^2/Clalpha.
Myquestion is : What is the difference between this above expression and the classical expression given by Cdi = Cl^2/(pi*lambda*e)
I ask this question because before reading your book, I considered for my problem, that the induced drag was given by the classical expression :
Cdi = Cl^2/(pi*lambda*e) but it is wrong in this case (0% suction effect), isn’t it?. If I have to do a state space flight mechanic model with drag equation, what drag do I consider?
Thank you for your answer
Regards
Jerôme bazile
July 5th, 2011 at 9:33 am
Hi guys, this is not Dr. Raymer but I would like to help if I can.
Brad: I think Dr. Raymer is right not to release is books as ebooks as the viability of this technology is frequently being debated and like everything else digital it is constantly under attack from pirates.
Jerome: Any expression you use for Cdi will only be an approximation and even CFD should be verified with wind tunnel testing. You need to do a bit more research to find the expression you are comfortable. ‘Fluid dynamic drag’ by Hoerner is the leading text which will give you a more in-depth drag analysis.
Hope this is ok. Don’t mean to offend Dr. Raymer, just keen to help out.
July 11th, 2011 at 1:04 am
Hello Adrian, thank you for your help, I’m an engineer not a pirate!. The aim of my purpose in my previous question was not to offend Dr. Raymer and I apologize if it has been understood like that. Nevertheless I think Dr Raymer and others are considered as “well of learning” in Aircraft Design, and my last question was a simple question to improve my understanding of a particular problem, that all!
Jérôme
July 12th, 2011 at 4:12 am
Hello Jerome
Sorry there was some cross confusion. My first comment was a reply to a question from Brad about whether Dr. Raymer should release his books as ebooks. The comment wasn’t meant for you.
Hope the drag estimation is going well. You might also like to have a look at the free vortex lattice program AVL. I know some people who have been getting some quite good results from it and it is able to determine drag and stability coefficents.
All the best, Adrian
July 15th, 2011 at 2:28 pm
Hi, Everyone,
Sorry I’ve been AWOL for so long. I’ve been working 24/7 on “Project-X” of which you’ll hear more soon. Then I got tapped to give another presentation at EAA’s AirVenture (Oshkosh), in addition to the three I’d already agreed to. It should be interesting – Simplified Structural Design for Aircraft Homebuilders – but the preparation time was way more than I expected. All done now, and I hope to see you there.
DPR Reply to Roy: L/D for a normal climb is calculated the same way as for cruise. While there is a slight difference due to the climb angles, it is trivial unless you are climbing at an extreme angle. So, you just need speed, weight, and the aero coefficients, at the climb speed. And yes, when a climb gradient is given in percent, you must divide by 100.
Thurai Rahulan said “Is there an obvious reason as to why the spanwise distance of the mean aerodynamic chord (MAC) of the fin from the fuselage reference line is twice the value calculated from the standard formula?”
DPR Reply: That is something I need to clarify in my book. For a vertical tail, aspect ratio is defined the same, ie., total span squared divided by total area. Taper ratio is still tip chord divided by root (base) chord. Where it gets weird is the spanwise location of the MAC (Y-bar) which is doubled for a vertical tail. This occurs because the total area is half the value you would get if the vertical tail were to be laid flat and converted to a “wing.”
Arasch X. Says: “I have question about carpet plotting. When we assume a pair of (T/Wto,Wto/S), how we calculate Wto with this pair? “
DPR Reply: That is the whole process of sizing. I think you need to go back to my book and review this section. If you have a specific question, ask again. Sorry…
Antony Says: “Is there any relation to determine the weight at each point in a wing”
DPR Reply: There is no easy way. To get a good answer you have to approximate the actual design of the structure. As a quick answer you could assume that the weight follows the wing taper. The lift distribution can be estimated by Schrenk’s Approximation, in my book.
akspas Says: “How important or significant is the bow tail angle in shaping an military aircraft especially in the rear portion of the fuselage. How this angle is related to the performance of the aircraft.”
DPR Reply: Boat tail angle, the final angle at the back of a body such as a fuselage, has an important effect on drag, which affects performance. You don’t want it to be too high. There is no hard rule, but more than about 12 degrees makes me nervous for most types of design.
Graham Fyfe Says: “Simplified p.23, Tip Speed. What is V?”
DPR Reply: Easy one – Velocity in ft/second
Bonfi Says: “What do you think about materials to build models that have a higher g”
DPR Reply: Actually, you can get higher g levels with any material. The problem is weight, and new materials such as graphite composites are allowing higher g values with much less weight penalty.
Richard Siers Says: “…Is it o.k. for me to sell the second one?”
DPR Reply: No, you must bronze it and instruct your heirs to place it lovingly in your casket when you die, so that you can enjoy my wisdom for all eternity. Kidding. Of course you can sell it, and I hope you get a good price for it!
Adrian Says: “Can you recommend any really good books on structural design…”
DPR Reply: See http://www.aircraftdesign.com/books.html#Tip5
Kyle Says: “…purchased your book “Simplified Aircraft Design for Homebuilders” I never got the free software for it”
DPR Reply: Go here (http://www.aircraftdesign.com/sadfh.html ) then scroll down a few lines.
Adrian Says: “Do you know of any good weight prediction methods for sailplane wings”
DPR Reply: Check http://www.sawe.org/ I seem to recall a paper on this.
Adrian Says: “I assume that the initial estimates that you use for wing dihedral are for the aircraft on the ground ?”
DPR Reply: Actually, those are based on older aircraft which do not deflect so much, so they would be appropriate for in-flight values. If your airplane wing bends like crazy, you need a “jig” or ground position significantly less. Not easy, and whatever is shown on the Dash-One drawing is just a pageholder for the right value to be determined.
Adrian Says: “Have you thought about writing a whole book of various design examples to suppliment your text book ?”
DPR Reply: I’m not sure that there would be enough of a market to justify the time. Besides, the AIAA has published many design example books, some of which are pretty good (being done by actual designers, as opposed to management and marketing people who present design as if the first thought the company ever had was perfect, and BTW, give us more money…)
Graham Fyfe Says: “One thing I do miss in Simplified ….. is wing tips. I could not find anything on the web on how to design a hoerner tip.”
DPR Reply: My textbook talks about wingtips quite a bit, but for actual design parameters for a Hoerner tip you should look up the original research. It is probably in German.
Brad Says: “…holding off buying simplified aircraft design in the hopes that you will come out with an ebook version…”
DPR Reply: E-books both scare and interest me. Once something is released digitally, a million people will steal it. My books are already pirated on-line, and I don’t want to make it any easier. If we eliminate all income from being an author, why should we write or update any books? On the other hand, a lot of people are sold on Kindle and the like. As Jack Benny once said, “I’m Thinking……”
Jerome Says: “…question concerning induced drag calculation in subsonic phase, describe pages 349-350…
DPR Reply: Induced drag is N*sine(AOA) only for 0% suction. It is CL^2/Pi*AR*e for 100% suction. For real wings it is somewhere between those, which we find from the empirical %LE Suction chart.
July 18th, 2011 at 7:35 am
Dr. Raymer.
I have a little question regarding tilt rotors that is, how can i calculate the power required in helicopter mode?
All the information that I have found is about single rotors not to double rotors.
I appreciate if you can help me.
Regards
Carlos.
July 18th, 2011 at 8:00 am
DPR Reply to Carlos: The right answer is, of course, good CFD. To a first approximation, you can analyze a multi-rotor helicopter like a Tilt Rotor as if it were a big single rotor with the same total disk area (see my textbook). There will be much greater power losses than for a normal single-rotor helicopter, due to the extra gearboxes and shafts. I’d guess about 5% more, but it may be double that. Does anybody have a better number for this?
July 18th, 2011 at 2:22 pm
Dr. Raymer.
Thanks for your answer. However, There is an another question. what about the aproximation using normal formulas and what book are you recomending.
Thanks again.
Regards
Carlos.
July 18th, 2011 at 10:27 pm
Thank you Dr Raymer for your answer.
That means somewhere with DLM in stationnary fied, it is impossible to provide suction effect when we have a prescribed downwash.
There are somwhere two kind of problem :
The analyse problem : The spanload is known and one calculate the aerodynamic derivative and the inducd drag as N*sine(AOA) with for 0% suction.
The design problem : One calculate the wing shape and the spanload to have a induced drag given according to CL^2/Pi*AR*e for 100% suction
I’m right ?
Thanks again
Best regards
Jerome
July 18th, 2011 at 11:20 pm
Reply to Carlos: I like the book by Prouty - see http://www.aircraftdesign.com/books.html#Tip4
Reply to Jerome: Sorry, I don’t understand your sentence about “DLM ” and I don’t know what a “prescribed downwash” is or why that might prevent suction. Perhaps you are familiar with one of the classic aero theory methods and are attempting to apply its terminology to this very-different method. Kindly review my book in detail.
July 19th, 2011 at 1:59 pm
Dr. Raymer.
I was looking at the book ‘Aircraft design: conceptual approach page 632′, how is the procedure to resolve the momentum theory with out tail rotor and transition mode?
Thanks once again
Regards
Carlos.
July 20th, 2011 at 12:15 am
Sorry, I don’t understand the question. Page 632 discusses the approximate method for analyzing helicopters in forward flight, treating them like airplanes. It doesn’t mention momentum theory.
When using momentum theory for hover or vertical climb, an allowance must be included for the power used by the tail rotor.
Helicopter transition mode analysis is very complicated, and is best left to sophisticated helicoper analysis computer programs.
July 21st, 2011 at 11:40 am
Dr. Raymer,
I have a question regarding the technical aspect of the aircraft design in CAD.
I have done surface modeling in general off of 3 view drawings and such, but that was based off of existing planes. However for a class project our design was done in separate parts, and then was assembled.
My question I guess is in Industry, how do they go about designing the initial shape of aircraft, is it a top down method where you simply design the surfaces and see if components fit ? ( based on that modifications take place ?) or different parts are designed then put together ?
Sorry for the lengthy message.
Also regarding Oshkosh my plans of attending your talk got messed up, my friends however are going. Are you supplying any printouts of your presentation over there so my friends can grab me a copy ?!
Thank you for your time.
July 21st, 2011 at 10:38 pm
I purchased the following product from American Institute of Aeronautics and Astronautics:
“Aircraft DES 4E & RDS-STDT 5.1″
Account Number # 44391
Invoice Number # AIA1033347
I followed the instructions given in the deployment manual, which says that the contents need to be copied to a local drive and then an attempt to be made to run the RDS executable. Alternatively, use Install executable to use the wizard to install. I tried both options and each time there is a popup messagethat comes up which says
“This system does not support fullscreen mode. Shoose ‘Close’ to terminate the application”
Kindly point me to the steps to resolve this issue or the right person who can provide guidance.
July 24th, 2011 at 5:29 am
Are there any good dedicated tools for mass properties and CG estimation for components and aircraft as a whole. Any recommendations. We use Catia V5 as a design tool.
July 26th, 2011 at 8:58 am
I have just read the forward to the book ‘Airplane design’ by Karl Wood, as recommend by Dr Raymer. Highly recommended, very funny. Perfect for de-stressing any of you guys who have got exams at the moment. It is not that far from the truth in industry either, that makes it even more funny.
akspas: I just noticed you comment about wanting CG and mass estimation. If you are already using CATIA V5 then you have everything you need. Look on the toolbars at the bottom of the screen, you will find measure and mass properties etc. All you need to do is input the density. For other non-structural components use Dr. Raymers book.
August 10th, 2011 at 10:09 am
Reading through AD:ACA and I like the readability, but I didn’t know the F-86 took off with the speed brakes deployed (p.85). Is this done to minimize unused runway?
August 10th, 2011 at 10:32 am
Reply to Kareem: We design the insides, the outsides, and the internal components all at the same time. That is the difficult part of my job. My textbook attempts to explain it, but to some extent, good designers are “born” not “made.”
Reply to Achan: Sorry for the trouble. See www.aircraftdesign.com/rdstips.html#Tip51 and www.aircraftdesign.com/rdstips.html#Tip3
Reply to Akspas: My RDS software has a good routine for conceptual-level weights estimates. Beyond that, check at www.sawe.org.
Reply to Adrian: Codes like CATIA do mass properties given 3-D CAD geometry and an input density, but aircraft component estimation is a lot more complicated than that.
Reply to Ted: To make the book more interesting, I asked AIAA to insert stock aircraft photos in otherwise-blank areas. I didn’t get to see the captions before publication, but I’m not sure I’d have caught that subtle mistake (obviously, it should say “landing”). The first edition of the book confused an F-15 with a B-1.
August 10th, 2011 at 1:41 pm
Any process that confuses an F-15 with a B-1 obviously needs proofing. The speed brakes actually jumped out at me.
August 11th, 2011 at 8:55 am
Weight estimation methods suitable for the conceptual design stage are an interesting area which is continaully developing. Obviously in the case of off rubber engines etc you have to rely on statistical predictions etc.
In the case of aircraft structure such as a wing spar, don’t you find that the mass estimates from the conceptual design stage are only sufficent to help get you started. Then as the design evolves and such components are at the detail design stage then you are able to obtain better estimates with CAD systems such as CATIA. Even then though, the mass of the actual part can still differ considerably, as I have discovered myself.
I heard that the prototype of the B747 was seriously overweight which necessitated a fair amount of remedial work. The big companies now apparently use their own in-house weight prediction codes which are significantly more detailed and complicated and obviously not available to anyone else.
This is such an interesting subject though as it has such an impact on conceptual design work. Don’t you find that at the conceptual design stage, you sometimes just have do the best you can, especially if it is a novel design.
August 11th, 2011 at 9:18 am
By definition, “Conceptual Design” is to get you started, and the methods used in conceptual design are superceded by more detailed methods once you have the overall aircraft concept defined and optimized to the requirements.
We always just do the best we can! And often, due to wishful thinking as much as anything else, the actual weights end up higher.
August 11th, 2011 at 6:00 pm
There is deffinatly plenty of fun when the aircraft starts to come together.
When there is a slight mis-match between the centre of gravity of the actual aircraft the original estimates, the engineer that breaks the news to you that the nose cone is seriously overweight is instantly your best friend. The propulsion engineer with his ultra heavy all singing and all dancing variable geometry exhaust nozzle on the other hand is not so favoured.
August 14th, 2011 at 11:54 pm
We are never happy if any part of the aircraft is overweight. Even if, say, the airplane comes out tail-heavy and we need to add ballast weight in the nose, we’d rather do it that way than have some part be heavier than it must. Ballast we can adjust, place as far forward as possible, and later possibly remove. Overweight components don’t have that flexibility.
Somehow I’m reminded of the expression “beauty is skin-deep, but ugly goes clear to the bone.” I don’t know why. I guess all weight is “ugly” to an aircraft designer.
August 17th, 2011 at 2:17 pm
This is where the real difficulty comes with novel aircraft configurations which incorporate advanced technology systems. The final weight of the systems is to some extent outside our control when it is developed by a different compnay or department. Timescales unfortunatly dictate that the airframe must be developed in conjunction with the systems and so there can be quite a bit of head scratching at the end. The big players in the business have such an advantage in his respect.
On a different note. I have been looking over some pictures of some of the aircraft displayed at the EAA events and am impressed. Especially to think that some of these are developed by a one man band. It raises the question how much talent out there is going un-noticed.
August 17th, 2011 at 3:57 pm
I have just graduated with a first class degree in Aeronautical engineering from the U.K…I used your book AD:ACA as a reference source for my final year dissertation and it was really helpful….Thankyou for writing the book…I am keenly interested in aircraft design…but now sometimes i think that i should have done my dissertation in something more realistic area for e.g. stress engineering (Stress engineering has a lot of scope in the UK) In my opinion, i have quickly realised that there is no thing such as conceptual aircraft designer jobs in the U.K. I think the closest one can get is to become a aerodynamics research engineer (Well i might be wrong..can’t see aerodynamics jobs for a graduate to start off in that field)…I have secured a place for MSC in Aircraft design at cranfield, even if i got to study there i think it is just a waste of time and money…Should i just start working at anything i come close to???? or go to uni in hope of becoming aircraft designer which does not sound realistic??? Any ideas would be helpful…Thankyou…
August 17th, 2011 at 10:04 pm
Nobody goes into aircraft conceptual design because a careful study of alternatives showed that the field has the best chance of a job. We do it because we love it.
For some of us it does turn into a long, enjoyable, and fairly profitable field. For others, they just never get their “break” and wind up doing other things.
And yes, there are conceptual design engineer jobs in the UK. In a month I’m going to Wharton to teach a class to a bunch of them. But no, such jobs aren’t plentiful, in the UK or anywhere.
If you do go for the MSC at Cranfield (great school!), you may want to take a lot of other classes in aero and stress as well as the design curriculum. Those fields are very important for conceptual designers, and if all else fails, you can “reposition” your resume towards one of them.
August 18th, 2011 at 4:46 am
Thanks a lot for the advice, Now i know what to do..I am currently reading airplane war stories by Dr Jan Roskam. I am really amazed by his hard work and dedication for airplanes throughout his life. I mean who could have thought a Dutch guy would be a world recognized aerospace engineer. To write 8 books in airplane design, 2 huge books in stability and control, one in airplane aerodynamics and performance and a biography is just incredible. I can’t wait to read your ‘Living in the future’. These are the kind of things that keeps inspiring a whole new generation. Thank you.
August 22nd, 2011 at 7:22 am
Sorry to interupt Dr Raymer, please excuse me.
Renzo: I am also from the UK and am also trying to break into the field. I did the MSc at Cranfield and would be happy to share my exeriences with you either in terms of the MSc or the UK aerospace job market if it is of any help. I was trying to get into the US myself but have given up as it is very hard for potential employers to get a green card for you apparently so they stick to US nationals only. If you want to have a chat then please e-mail me. I have put my e-mail below but Dr Raymer might be happier to send it to you directly.
biggles74@yahoo.com
August 23rd, 2011 at 11:58 am
Hi Dr Raymer,
Are you going to update the student software to run on windows/64 bit or MAC?
It really would help in this day and age!!!
Thanks for publishing so much great info on your site too.
August 27th, 2011 at 12:02 pm
Dr. Raymer,
Back on July 15th you gave a hint of what you were working on, a “Project-X”. Any chance for additional hints or a date when we might learn more?
August 28th, 2011 at 3:00 am
Rowan - Currently you can run RDS-Student on any version of Windows including 64 bit using DOSBOX. People tell me they can run RDS on a MAC using a DOS emulator, but I don’t do Apple so I don’t know myself.
Nathan - If I told you, it wouldn’t be “X” anymore! But a hint….it just might make Rowan happy.
August 28th, 2011 at 12:01 pm
Hello Dear Sir.,
My name is Sparsh Chokshi, I recently bought your RDS Student software for A/C design. I have a window 7 software which is not letting me install the software on my laptop. I did follow the website in downloading DOS BOX. 32bit. which recommend on your website. I did follow all the steps but yet the command prompt keeps saying file dose not exist.
I was wondering if you could please help in installing you software on my lap top. Or may be guide me in more detail how to go about setting up the program on my laptop.
Thank you very much for your help .
Sparsh
August 28th, 2011 at 9:17 pm
The obvious question - you downloaded 32-bit DOSBOX. Do you have 32-bit Win7?
There must be a reason DOSBOX cannot even find your RDS.EXE file. Double-check what you’ve done versus the instructions on my website and on the DOSBOX website, and try it with the simple program you can download at http://www.aircraftdesign.com/rdstips.html#Tip4 .
August 29th, 2011 at 5:22 am
Dr Raymer- HURRY UP!!!! :-)
I am happy to do beta testing for you if you would like. I do run Parallels on a mac and it does work, but the mouse movement is lumpy in the CAD module- you dont get nice smooth infinite movement. The rest of the program seems to process ok, as far as I have tested it.
Cheers,
Rowan
August 29th, 2011 at 8:56 am
Sir, I have been reading the correspondance with Renzo above and thought it would be a good idea to add a few comments about the state of the UK aerospace industry. In a short, the UK industry is hanging on my its finger nails and is near impossible for the majority of UK graduates to break into.
To give you an idea,
December 2010 - BAE Systems announced 1400 job loses
August 2009 - GKN announced 3600 job loses
July 2011 - Bombardier announced 1400 job loses
December 2010 - Augusta Westland announced 600 job loses
Rolls royce makes job cuts every single year
The market is hard for engineers in general and even more so for graduates. The vast majority of aerospace graduates do not end up working in aerospace. The lucky ones will find jobs low level jobs designing access panels etc. Although a number of companies do have graduate schemes, there is probably 1000+ applicants for 10 jobs. There is still jobs advertised for experienced engineers with 5+ years experience. There just is not the opportunities to get the experience.
Myself, I have a BEng, MSc and PhD in aircraft design and can not break into the industry. I have even tried volunteering my services to companies to get some experience but still nothing.
On top of this, about 3 out of 10 houses now being sold in the UK is being sold by the banks as a repossession. It is not possible for people from the UK to get jobs in the US due to the strict green card system. Any US job is now advertised for US nationals only. If anyone is thinking about doing a Aerospace engineering degree, I would think very carefully. It is a fun and enjoyable course but don’t expect to be doing that kind of work at the end of the course.
Would the last person out of the UK please turn out the lights.
August 29th, 2011 at 9:42 am
Adrian - that’s a little pessimistic I’d say, but obviously you are speaking from the heart. As I’ve said many times and many places, we don’t go into aircraft design based on a rational analysis of career options, but because we love it so much that we almost have to.
I was lucky - I went to college just as a huge aerospace downturn began, and graduated at the start of a sustained upswing with relatively few new grads competing for the jobs - they’d all switched to other fields.
But is this time different, and there won’t be an upswing, at least for certain countries? I don’t know.
One thing is true - these days it is very difficult for educated professionals to get a US Green Card and a legal work permit unless there is a family connection. But if you follow the widespread “illegal” route, you aren’t going to get a high-tech job anyway. Then if you do get that Green Card, you will have a hard time getting work at a US company that deals in military matters, or even at a pure-civilian company that uses ITAR technologies and such.
Now I’m the one sounding pessimistic……
August 29th, 2011 at 11:08 am
You are right, there certainly is no way I would have been able to do a degree in Business or Sociology or something like that. I doubt I would have lasted even 1 semester - far too boring for me.
It is dis-heartening to work really hard to learn all the topics and get all the qualifications and then when you get to the top of the ladder you just find a brick wall. At least I have tried, if I never tried then I would have alwasy gone through the rest of my life never knowing. We never know what tommorrow will bring either. In life we have to take one step at a time and keep moving forward with what we have.
It is so frustrating when I look on the US job boards and see loads of jobs I really want to apply for, you guys are so lucky over there. Maybee the answer is to get re-married to a US lady. On the other hand, I have heard that the US police are very strict when it comes to motorists.
Bring back the days of Handley Page, the Short Brothers, Supermarine and the like. It seems that all these little companies got swallowed up by the big aerospace giants and then the big companies themselves shut down.
August 30th, 2011 at 12:53 pm
Hello Dr. Raymer,
Thank You very much I will check it out what I have done wrong and follow back with you.
Sparsh
August 30th, 2011 at 2:19 pm
Yeah there are loads of opportunities in the U.S. But over here when you look for graduate schemes in aeronautical disciplines the results are just frustrating and I am talking about the famous gradcracker.com here:
Caterpillar UK (Building constructing products division)
Unatrac (Established caterpillar dealer)
EDF energy (Low carbon electricity)
Aggregate (Again Building construction company)
IBM
When we studied our aerodynamics and aircraft conceptual design tutor once said “you will never be lucky enough to apply what you learn. Graduate only means you have the ability to learn new skills”. Now I understand what he meant.
August 30th, 2011 at 2:51 pm
Renzo: Have you thought about joining the airforce as a graduate aircraft engineer? The airforce does send some of its engineers to Cranfield to do the aircraft design course and it is all paid for. I wanted to go down that route myself but was told I am too old as you have to be under 30 to join.
The reality is that the majority of people with engineering degrees in the UK do not end up in the job they wanted. Don’t overlook other opportunities while looking for a job as you could run the risk of ending up with nothing. I need to take my own advice onboard as well.
September 16th, 2011 at 9:37 am
Hi Mr. Raymer.
first, i can not write english well. i bought two of your books and i really enjoy it.
Mr. Raymer ,on your raymer simplified aircraft design spreadsheet i read your note on A-OPT sheet : Enter delta on Weight sheet (I stuck it in the unused Anti-Ice entry), and change aspect ratio and empty weight “a” factor on Initial Sizing Sheet. i do not understand about ” unused anti ice entry “, which one ( row and collum ) ? then, i read ” ! ” on weight sheet ( H 19 ), is it wrong or no problema ?
reply please or send me email
thanks
ade hendra
September 24th, 2011 at 12:29 pm
Ade - This design doesn’t have anti-icing equipment so that standard category on the weight sheet is blank (cell G13). When adding weight for the trade study I used that blank, unused spreadsheet cell to add weight the easy way.
H19 is the calculated empty weight CG location.
September 27th, 2011 at 4:02 am
Hi Mr. Raymer,
i am doing bachelors in Aeronautical Engineering,its my 4th year and its been pretty good till now,but now i feel like i don’t know what to do after this,since i am studying in China i don’t think i can apply for job here,i need to know Chinese very well to get a job here,i am always searching for different university for masters,but i don’t know which one to choose or not to choose at all.
Any suggestion would be helpful for me in this state.
Thanks in advance.
September 27th, 2011 at 6:29 am
Roshan - To attend a university in the USA is sometimes difficult. The visa may be hard to get, and the universities here do not always recognize the education in other countries as equivalent.
I’m very familiar with Cranfield in the UK - great school with a lot of international students. The same is true of KTH in Sweden, where I did my PhD, and doctoral work must be done in English. I know there are some excellent aeronautical universities in Germany and France but I’m not familiar with their programs as to language and international student matters.
October 1st, 2011 at 11:28 am
Hello, hope you are keeping well
I was looking at the planforms for BWB’s and the cranked wing planforms as used on the X-47B and have got myself confused with the concepts. The inboard section of the wing functions as a delta wing with good high speed performance but poor efficency. The outboard section on the other hand functions as a high aspect ratio wing with good efficeny at lower speeds. The crancked wing is thus a compromise between the two.
However, at high speeds, if the inboard delta section is the most effective, won’t the outboard sections be ineffective in comparision and adding drag to the aircraft since they are opperating outside their optimal flight regime? If they are protuding outside the Mach cone generated by the inboard section then there will be additional problems?
I can see how LEX’s help at low speed but in the high speed regime it seems a much more complicated ball game.
October 1st, 2011 at 11:47 pm
Hi everyone,
Can someone please advise me on the best method to come up with thrust to weight estimates during preliminary design? I don’t want to get too techy yet because my team and I are making assumptions at this point of our design.
October 4th, 2011 at 7:17 pm
Mr. Raymer,
Hello. I have both a copy of SADH and your textbook (3rd Ed). I’m curious about a paragraph on page 30 of SADH, discussing dihedral. The last sentence states “Watch out–if the dihedral break occurs much more than 50% out on the span, you can get excess and maybe uncontrollable rolling near the stall.”
The design I am conceptualizing (one-off homebuilt btw) is a high-wing motor glider with wing extensions set at a greater dihedral angle than the main wing, so naturally this statement caught my attention :-) However, I haven’t been able to locate any material that really discusses ‘polyhedral’ wings, and in particular, any unique aerodynamic effects thereof. Would you be able to point me in the direction of some material that would explain the effect SAHD mentions in more detail? Thanks!
October 23rd, 2011 at 11:32 am
Mr. Raymer,
first I have to say how grateful I am that your website is so helpful for aircraft design engineers. I am an Undergrad Aerospace Engineering Student and I want to go for a Master’s degree but I don’t know what to look for. since, I am also a pilot I think I would want to go for test flight engineering, but my dream is to design aircraft, from your experience in the industry do you think that test flight engineering would be a good choice if my ultimate dream is to design aircraft, or would you recommend something else for my Master’s degree?
November 1st, 2011 at 6:17 pm
Mr Raymer,
I’ve read through your book on Aircraft conceptual design and I must say that it’s almost like a bible to me now. I hardly go to class without it now. It’s one of the best aerospace books I’ve read period. However my question revolves around a UAV. I am currently designing a UAV that’s suppose to carry 1800 lb of cargo. However, during the initial weight estimate, I ran into some difficulties with the empty weight fraction estimate as there is no model for a UAV (chapter 6 of initial sizing). I tried to use the twin turboprop model but that appeared to be too heavy. Do you have any suggestions as to a good empty weight fraction estimate?
November 4th, 2011 at 12:57 pm
Dr. Raymer,
I am designing an R/C aircraft for recreational use. I am planning to use an inverted V tail mounted on twin booms. I was wondering if there are any ruddervator sizing guidelines that you know of for such a tail configuration.
Thank you,
Thomas
November 11th, 2011 at 4:14 am
Hi Dan ! how you doing ?
I would like to submit you a scanned rough, of a new aircraft concept and idea.
Target: Sport and Fun primarily but it might be developed for Military
purposes.
Really a rough drawing, but I need you to confirm, if I can send it , via this blog ?
Or shud I attach it to your personal e-mail@mail.com ?
The promptness of your reply shall be very much appreciated
Alex
December 17th, 2011 at 12:30 pm
Dr Raymer,
Im still playing around with RDS on a Mac. Here is something i found which might be valuable to mac and PC users who use dosbox:
To increase the speed of dosbox cpu permanently, rather than using cont F11/F12, go into the dosbox-0.74.conf file and change the following two settings:
Core=dynamic
Cycles= max
RDS will run so damn fast it will defy logic!!!
Also I notice you can get dosbox for mac now. I ahvent bothered to go through the setup, but it looks like it is another way to run on a mac without bootcamp/parallels etc.
Cheers,
Row
January 6th, 2012 at 12:17 pm
RAYMER REPLIES:
Adrian Says: … cranked wing planforms
Raymer Replies: BWB and X-47 have those low aspect ratio center sections just to provide volume for the cargo, not for aerodynamic efficiency. The true aspect ratio of the whole design is essentially that of the outboard segments, extended to the centerline in a trapezoidal shape. The additional area inboard is mostly just extra parasitic drag. For a high-Mach airplane, the LEX portion helps with the shift in aerodynamic center. See my book.
Jay Says: Can someone please advise me on the best method to come up with thrust to weight estimates during preliminary design?
Raymer Replies: Buy my book. Sorry…..
Bob Says: … material that really discusses ‘polyhedral’ wings
Raymer Replies: DATCOM has some methods, I think, but I’m not sure I’d trust it. Wind tunnel or CFD….
Sheldon Johnson Says: …do you think that test flight engineering would be a good choice if my ultimate dream is to design aircraft, or would you recommend something else for my Master’s degree?
Raymer Replies: Why not do your MS in Aircraft Design?
Rene Hamilton Says: …empty weight fraction estimate as there is no model for a UAV
Raymer Replies: Do your own. Get data from Jane’s or off the internet (be careful!) then plot it over top of my graph. Eyeball a straight line, and match an exponential equation to it.
Thomas Says: R/C aircraft for recreational use… inverted V tail mounted on twin booms… ruddervator sizing guidelines
Raymer Replies: For a model airplane I’d use 35% then reduce gain if it is too touchy.
And Thanks to Row for help with RDS on a Mac
January 25th, 2012 at 9:32 am
Question for my aircraft design friends: My RDS-Student software now comes with a book-sized paperback user’s manual. AIAA wants the next version to rely on the callable PDF manual, with only a little jewel-case booklet for a physical “manual.” Obviously that saves some money, but will purchasers feel cheated, or be less likely to buy it? I feel that way, but I’m old…..
January 26th, 2012 at 12:26 pm
Hello
I am a bit old skool and like to print PDF manuals off before I read them as it gives me a headache stairing at a computer screen for long periods. I am also a bit stuck in my ways. The vast majority of manuals these days come in PDF form though, which is not too bad if you have got 2 monitors set up on your computer.
On the plus side, you are able to search through a PDF very fast and you can include as many colour screen shots as you like. On a final note, if the manual is in PDF form then if you happen to spill a cup of coffee over it then it doesn’t matter as you can just print a new copy off. In that respect I would prefer it to be in PDF form.
Hope this helps
January 28th, 2012 at 3:14 am
Personally, I like hardcopy, but everything is going pdf to be honest. Just about all software, bar the really big stuff is pdf. You could do a pdf manual, then have a hard copy which has a quick lookup guide/ even more data in it as a seprate purchase maybe?
I guess if people want to have a hard copy they can print.
You have an IP issue too- pdf will end up on the filedownload sites in no time!
value for money… if you take the hard copy away, how about adding a little more functionality to the student version? Like a 3D geometry file for the model so it can be imported into an animation program/ surfacing etc for presentations… that would be cool….
as an aside,
I am struggling using student at the moment as my signed copy of Aircraft design is sitting on a bookshelf at home in Australia, and Im bouncing between the UK/USA working!! Hard to check the nonclemature from 1/2 a world away! An abbreviations lookup list with short description would be cool.
anyway, just ideas. either way Ill still use the program!
January 28th, 2012 at 6:57 pm
I would say that the average reader/user will not feel cheated in just a .pdf version of the user manual. It doesn’t take much to print it out and hey I all for saving on paper myself.
January 28th, 2012 at 8:24 pm
Any more opinions? While I lean towards a real manual, the voting is mostly in the other direction and the AIAA prefers it, for obvious reasons. Cheap…..