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malte

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Hi fellow dreamers.

I have a broader question where I'd like to hear some opinions and arguments from you.

I have a M.Sc in aeronautical engineering (RWTH Aachen University) and am working in certification of aircraft, having been part of the EASA certification of five aircraft to differing degrees and a few STCs (most of which are also FAA certified).

I now have a Lake LA-4 in restoration after a hard water landing ("just" assembly to be done by now), a MJ-2H Tempête in restoration (electric system, magneto overhaul, some minor wood works and assembly / new flight testing needs to be done) and a Ka-1 Glider (minor woodwork, covering, instrumentation, steering cables, reinstallation of metal parts and assembly to be done). So my workshop-time is full for a year or so.

However, I would like to build and design from scratch. Although having certification experience, I haven't done that, yet (university exercises in spar-building or aircraft sizing don't count).

I do know, that it takes considerable design time (especially if working low paced due to the other projects). Jean Delemontez once said he needs about two man-years to design an aircraft and despite the easier access to computers, I can't even keep a straight face if I were to claim that I come close to that. So whatever I would do, I won't cut wood/glass/metal within three to four years, I think.

One of the planes I have in mind is a glider capable of unlimited aerobatics. Two seats, if possible self-launched (perhaps electric) but that's not definitive. Might consider designing for kit production, but that, too, is not set in stone.

However, a frp-unlimited acro glider is not trivial, even if systems are much simpler than - lets say - on a raptor ;-). The flight dynamics can srew up a design, the loads are high and you don't want to have any unexpected behaviour.

Given my low experience in designing, I thought, why not design something at first, where you don't even need a computer. Get acquainted to the process by designing something simple. Jodel D9 / Stark Turbulent / Taylor Monoplane / Evans Volksplane style of aircraft. Perhaps openly work by hand and showing the design principles behind simple designs. I love these little flying fleas as much as the acro gliders, so my devotion would be into the aircraft, too.

Would you go directly into the more complicated project, or start easy? Would you stick to one final materiel (FRP) or would you consider using other materials (metal/wood)? Would you be open (not only one way but also open to critique and change) or design with a good reviewing friend?

Questions over questions...

I probably will do what I want to do anyway, but good arguments will shape that goal and path, I think.

Thanks a lot!
Malte
 

BJC

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I can not find, in what you wrote, the reason that you want to design an airplane. My answers to your questions about what to design and what material(s) to use will depend on your intent.

One question that I can answer though, regardless of intent, is whether or not to get peer review throughout the process. Yes, get quality peer review.


BJC
 

Jay Kempf

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Dream aircraft with infinite performance and budget? Intellectual experiment? Mission dependent design? 1 place? Airbus size?

Oh to have been Howard Hughes back in the day with infinite budgets and infinite performance goals.

Aachen is a beautiful place. Haven't been to through there in years since the Cayenne was a prototype...
 

Hot Wings

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Would you go directly into the more complicated project, or start easy? << >>
Would you stick to one final materiel (FRP) or would you consider using other materials (metal/wood)? << >>
Would you be open (not only one way but also open to critique and change) or design with a good reviewing friend?
Is this for profit or fun? Trying to mix both and have a good outcome is probably as hard as building a flying car that is good at both tasks. If this is for pleasure pick the one that makes you happy each time you start sketching a new part.
<< >>
Use what works best for the job. Example: a piece of wood is good enough for the nose gear skid on Spaceship One.
What works for the job, if being built for pleasure, may be different than what is the most cost or weigh efficient.
<< >>
Build what YOU want - but get a second opinion/peer review at critical points in the project and consider any suggestions seriously even if they mean a significant change is plans.
++++
And what TFF said. If this is a homebuilt a lot of the little details don't need to be documented and tested to the same degree that is required by a certification process. TLAR engineering IS appropriate in some cases where the designer/engineer has experience and "feel" for the task and optimization is not a priority. Just test to make sure.
 

pictsidhe

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And now you know you thought wrong...:);)
It is and it isn't. I'd certainly recommend staying away from from a 'hot' design to start with, though. An ultralight does need extreme attention to weight, otherwise, it is less critical in most areas than the bigger stuff.
I'm not making my job any easier by designing for potential production. Some cheating will happen for Mk1.
 

malte

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Thank you all for the input so far!


I can not find, in what you wrote, the reason that you want to design an airplane. My answers to your questions about what to design and what material(s) to use will depend on your intent.
Well I guess the reasons are the same as for many other here on the board: Out of interest, fun, to further learn, to write my name on a plane ... "just because". If I wanted a flying flea cheap, there'd be plenty projects, restoration objects and flying aircraft waiting to be picked up for a bottle of scotch or two. Aerobatic gliders are harder to come by, but it's not impossible (the bottle of scotch just gets older and bigger).

One question that I can answer though, regardless of intent, is whether or not to get peer review throughout the process. Yes, get quality peer review.
BJC
Yes, sir, that's what I do professionally and that's what I will do on a project like this. I have a good community of knowledgeable aero engineers to CVE my design and I know here is a knowledgeable and interested peer group, aswell.

Don’t let your education get in the way.
I try not to. In fact, I have studied aircraft engineering because I was flying and tinkering with aircraft (especially gliders in the club) since an age of 13. I am an EASA A&P IA equivalent (up to 1200 kg MTOM), Flight Instructor and have restored some planes already.

Dream aircraft with infinite performance and budget? Intellectual experiment? Mission dependent design? 1 place? Airbus size?

Oh to have been Howard Hughes back in the day with infinite budgets and infinite performance goals.
I don't know if an infinite budget really would be so exciting, or not just boring? Anyway, the "intellectual experiment" pretty much sums it up, what I am aiming for. Single seat, perhaps two. More than that means to run a complete certification program in Germany.

Aachen is a beautiful place. Haven't been to through there in years since the Cayenne was a prototype...
The runway is considerabel larger now, so is the university. Since then, RWTH has a couple of additional wind tunnels, including some supersonic. They are fun to play with, but I left University eventually to go into the industry.

Is this for profit or fun? Trying to mix both and have a good outcome is probably as hard as building a flying car that is good at both tasks. If this is for pleasure pick the one that makes you happy each time you start sketching a new part.
<<
Mainly for fun. I don't mind if some of the cost gets recuperated, but there is no business model and no necessity to sell kits.

TBH I don't see a market for another flying low powered single seater kit aircraft. An aerobatic glider might see a few purchases, but even the Fox and Swift have sold only below 100 units. I am not stupid enough to bet that I will build and design a Game Changer in todays aviation history. Many more knowledgeable and more intelligent people with more money have tried that and failed.

>>
Use what works best for the job. Example: a piece of wood is good enough for the nose gear skid on Spaceship One.
What works for the job, if being built for pleasure, may be different than what is the most cost or weigh efficient.
<<
There is more than one way to skin a plane though. And the structural approach does differ between FRP, metal and wood structures, no?

I was concerned that building wood (that I know from repairs) would not give me the amount of training necessary to later build in FRP (that I also know from repairs and part production). OTOH, many design principles and processes are similar, no matter what structural layout with what material you chose.

>>
Build what YOU want - but get a second opinion/peer review at critical points in the project and consider any suggestions seriously even if they mean a significant change is plans.
++
Thank you. Wanting is plenty, though. I have learned over the past years to be critical of my biases. I am happy to change opinions and methods, if I am presented better arguments (but only then :) ) After all, this constitutes our certification principles.

++
And what TFF said. If this is a homebuilt a lot of the little details don't need to be documented and tested to the same degree that is required by a certification process. TLAR engineering IS appropriate in some cases where the designer/engineer has experience and "feel" for the task and optimization is not a priority. Just test to make sure.
[/QUOTE]
Yes, I already own an experimental aircraft. However, documentation is the least of the tasks and doesn't take up much additional time though.

I am starting with an ultralight. I thought it would be easier...
The amount of attention to detail is the same, if Ultralight or "normal" experimental or certified. After all, noone wants to crash due to design errors that can be avoided by proper testing.
 

Riggerrob

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Welcome dear malte,
Glad to hear that you already have plenty of education and plenty of experience restoring airplanes.

Start by defining your mission. Single-seaters are the easiest to design ... a mere two to four years of thinking, sketching, erasing, re-calculating, more sketching, etc. Most designers' first efforts are single-seaters. But do everyone else a favour by designing the cockpit around a 95th percentile man. The other end of the challenge is designing the cockpit so that a 5th percent woman can still reach all the controls.

Then prospective customers ask for two-seater variants.
Two-seaters only require a couple more years of calculations. Then the customer takes his wife for a couple of flights, then flies the airplane alone for the next few hundred hours. Even four-seater kitplanes (e.g. RV-10) fly most of their hours with only one or two people on board.

Once you have defined mission and number of seats, start reviewing various configurations.

Once you have narrowed down a single configuration, do preliminary sizing calculations.

Then decide on materials. Naturally, start with materials that you have the skills and tools to build. Then consider which specific parts work best in which material. For example, the Glastar STOL kitplane has sheet aluminum wings and tail surfaces, a steel tubing, roll cage around the cockpit and molded composite fuselage skins. Sheet metal is the easiest way to build flying surfaces because they are mostly single-curvature and easily pop-riveted together. Steel tubing is the best way to carry loads around the cabin of a high-wing airplane because of all the doors and windows (see deHavilland of Canada -2 Beaver). Finally, all the complex curves of the fuselage skin are easiest to produce (in large numbers) in female-molded composites.
Also be cautious about applying "black aluminum" thinking to composite components. By "black aluminum" I mean molding complex curves, bolting and riveting them together. You can save hundreds of hours of labour and dozens of kilograms of weight by gluing (epoxy resin) composite components together.

Finally, read Dan Raymer's "Simplified Airplane Design for Homebuilders" for a quick over-view for light, sport airplanes.
 

BJC

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Well I guess the reasons are the same as for many other here on the board: Out of interest, fun, to further learn, to write my name on a plane ... "just because". If I wanted a flying flea cheap, there'd be plenty projects, restoration objects and flying aircraft waiting to be picked up for a bottle of scotch or two. Aerobatic gliders are harder to come by, but it's not impossible (the bottle of scotch just gets older and bigger).
Got it.

With that, I suggest a nice single seat speedster that looks as good as Symmetry. Build in carbon and or glass, because you want a learning experience (or two - design and fabrication), and because of the smoothly transitioning shapes it offers. Keep it simple with fixed gear. Use a Lycoming IO-390. Make it strong enough for aerobatics, and have a Vd > 350 knots. Install the bare minimum equipment, upholstery, nicieties.


BJC
 

Chilton

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My thoughts, for what any of these opinions are really worth...
Work on the project which excites you, if you start on a simple aircraft design which does not do that you will find it much harder work than a more sophisticated design which you want to work on.
As for materials, I believe in using the one which will do the job at least weight and within budget constraints, we are fortunate to have a wide variety of options, and each has its own good and bad points, so it seems to me we should use the best option for each part.
 

pictsidhe

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Build something a little exciting for you. It gets tedious designing and building and being able to really look forward to the end result is very helpful.
Going for your ultimate aircraft may be just too much for your first project. Very few designers produce a truly outstanding plane on their first try.
 
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TFF

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If you are not in love, keep going until you do. My infliction is if I designed an airplane it would be a Pitts or a P-51 or Spitfire... I personally don’t have anything to contribute that I would find a reason for. You have to do it for love. If you are just a busybody, you could entertain yourself that way. I’m not; you have to give me a reason. Aerobatic sailplane or motorglider? People around here are picky.
 

malte

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[...]

Start by defining your mission. Single-seaters are the easiest to design ... a mere two to four years of thinking, sketching, erasing, re-calculating, more sketching, etc. Most designers' first efforts are single-seaters. But do everyone else a favour by designing the cockpit around a 95th percentile man. The other end of the challenge is designing the cockpit so that a 5th percent woman can still reach all the controls.
Well, there are two designs and I will, eventually, design both. The question was more or less about the order. First the aerobatic glider, or the simple puddlejumper? One has no engine but more complex flight dynamics, the other has an engine, but simple and well understood characteristics.

I am already a 95th percentile male, (see picture below) and that will be no problem. But it's a good hint to include the 5th percentile woman.

[...]

Finally, read Dan Raymer's "Simplified Airplane Design for Homebuilders" for a quick over-view for light, sport airplanes.
I have worked through his Book "Aircraft Design: A Conceptual Approach", through Howes "Aircraft Conceptual Design Synthesis", "Design for Flying" and "Design for Safety" from Thurston and "Introduction to Aircraft Design" from Fielding. Plus some papers, all for University and work. (You might be amazed, that you can identify the book based on the designs they produce. Raymer, for instance, tends to have a little too small elevators.)

[...]
With that, I suggest a nice single seat speedster that looks as good as Symmetry. Build in carbon and or glass, because you want a learning experience (or two - design and fabrication), and because of the smoothly transitioning shapes it offers. Keep it simple with fixed gear. Use a Lycoming IO-390. Make it strong enough for aerobatics, and have a Vd > 350 knots. Install the bare minimum equipment, upholstery, nicieties.


BJC
Hmm that's even more complex than a unlimited aero glider. I was thinking among the lines of a Jodel D9 for a starter: (But perhaps a bit more for my size).
1599077019154.png

Symmetry is - but please correct me, if I am wrong - not the typical aircraft to calculate on a piece of paper to reduce aircraft design efforts by simplicity.

My thoughts, for what any of these opinions are really worth...
Work on the project which excites you, if you start on a simple aircraft design which does not do that you will find it much harder work than a more sophisticated design which you want to work on.
Build something a little exciting for you. It gets tedious designing and building and being able to really look forward to the end result is very helpful.
Going for your ultimate aircraft may be just too much for your first project. Very few designers produce a truly outstanding plane on their first try.
Well, both options excite me. I am the donkey between two haystacks at the moment.
As for materials, I believe in using the one which will do the job at least weight and within budget constraints, we are fortunate to have a wide variety of options, and each has its own good and bad points, so it seems to me we should use the best option for each part.
Yeah, that sounds most reasonable.
 

cluttonfred

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malte, it's great to hear from someone with the passion, the education, and the resources to tackle a new project. While I agree with the comments that you should tackle something that interests you personally, so it will be more like fun and less like work, I absolutely think you are the right track with a simple single- or two-seater, probably a European microlight, but sized for taller and heavier modern pilots and designed around a readily available modern engine. Personally I'd suggest taking elements from the Evans VP-2, the Jodel D-11, and the Siebel S-202 Hummel to come up with a simple modern two-seater that looks easy to build, *is* easy to build and fly, and would attract people to say, "Hey, I could build that!" Tricycle gear, at least as an option, is probably a good idea. But you've probably heard stuff like that from me before. ;-)

PS--Bonus points if you can make it as cute as the D.11 prototype with a little radial!
 

Bigshu

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I'd love to see the Mini-Imp redone with plans in a more accessible style. The plans for the Hummel H5 are well drawn with full scale depictions of mostts. Same way with Zenith and I'm sure, other popular modern kits. I bought the mini-imp plans, and it's a mish mash of text and line drawings , and it just seems very opaque. My VP-1 plans are detailed, and even though there's not much full scale beyond fittings, the measurements and diagrams make it seem straightforward. The Fly-Baby plans I got online look like they'd be easy to build from, but those mini-imp plans make no sense to me at all.
 
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