A complete report on the aerodynamic and strength design of an ul aircraft

[christos]

My name is Christos and i am a civil engineer and aviation enthusiast from greece. First of all i would like to thank you all for your interesting and useful threads. It helped me throughtout the design. Now i am going to build my own design 2 seat ultra light composite aircraft. For the design and development of the aircraft all tools available to the modern engineer have been properly used.
This is the technical report of the design.


I posted it also in one other forum. I hope that you don't have any problem. Your forum and other was really helpful and i thank you about it


Best regards!

https://www.lisafea.com/citations.html
https://lisafea.com/pdf/Design_of_Ul...t_Aircraft.pdf (https://lisafea.com/pdf/Design_of_Ultralight_Aircraft.pdf)

I hope you like it :)

(original post) http://www.homebuiltairplanes.com/forums/showthread.php?t=30737

[christos]

I also made some animations
1)Pressures around the aircraft at speeds just before stall with fully extended flaps


https://www.youtube.com/watch?v=GBNkibjqPhs

2)Airplane hard landing (non-linear impact analysis)


https://www.youtube.com/watch?v=bR1gD2hSPAQ

It will be operate as ul in europe (it is light enough for uk's regulations) and as an lsa in usa

Best regards!

[thisadviceisworthles]

I can't add anything technically valuable, but it does make for an interesting read, and I cannot wait to read more about it.

[Bob H]

Christos;
Why did you choose 6.00 X 6 tires for a light plane? I would assume 5.00 X 5 would be more than sufficient for normal operations and would provide less weight and frontal area.

[christos]

Christos;
Why did you choose 6.00 X 6 tires for a light plane? I would assume 5.00 X 5 would be more than sufficient for normal operations and would provide less weight and frontal area.

Dear mr Bob,


I choose it because of better behavior and comfort on rough concrete surface. In near future i will change. But for the test flight i believe that it is safer a bigger tyre. I will operate from a rough concrete airfield.
Additionally i make this report to receive a flight permit, and i had to select tyres and i selected test's one. Of course i can change it. I am planning to change it after the test flight (if everything goes well).


Do you like technical report? It is a 100% computer design, i run in fea software every bolt every element and for computational fluid dynamics analysis i pay for a really strong computer. Last but not least i also ran a flutter analysis. It is an integrated design :)


Thank you very much for your interest!

[Bob H]

I spent many years working on composite manufacturing for aircraft. I didn't see any details of the actual composite structural scheme you used; skin/stiffener, sandwich. Or any fiber/matrix choice.
I fly a Pulsar experimental with E-glass, 10 mil sandwich skins and 1/4" honeycomb overexpanded core. Very light/stiff structure. Used 180F cure epoxy resin matrix.

[David Bally]

I am not an engineer but question the use of the NACA 66-009 airfoil. Although this airfoil has a very low drag coefficient in the very narrow laminar drag bucket it also has a poor lift to drag ratio. My understanding is that an airfoil with a better lift coefficient would allow the use of less wing( less drag ) and have better flight characteristics from cruse through stall. The NACA 66-009 would have a root thickness of approximately 0.117m or 4.5 in which would need a very strong spar at the root and have very little room for fuel. Also wouldn't the flaperons on such a severe stall airfoil cause an adverse yawl stall spin scenario?

Otherwise it should be a good motor glider and excuse my ignorance.

[christos]

I spent many years working on composite manufacturing for aircraft. I didn't see any details of the actual composite structural scheme you used; skin/stiffener, sandwich. Or any fiber/matrix choice.
I fly a Pulsar experimental with E-glass, 10 mil sandwich skins and 1/4" honeycomb overexpanded core. Very light/stiff structure. Used 180F cure epoxy resin matrix.

Dear Bob,


It is a technical report of aircraft's analysis and i didn't include structural details.
I am proud and lucky to discus with you because you have a lot of experiense. This aircraft will have a little greater top speed and lower stall speed than pushar because of their design. You will understand if you take a look at cl-aoa graphs.
About structural analysis, only a few aircrafts are so well analyzed. Finite element analysis of structure is high level, it is as good as a car's one.
About skin etc, itsn't so simple to me to answer in your question because it combine a lot of deferent materials, high strength pasticity zones, a combine of uni kevlar-carbon epoxy sandwich, in the first front area, high strength zones around passenger, a combine of carbon bars and glass epoxy laminate, wing spar, a combine of carbon tubes in high tension areas and epoxy laminate, it is only a simple report. This design is more complex than you believe.
I am a civil engineer i studied in university for 5 years and i also have a cfd analysis certification. But i would not do it if i had not some good friends whose helped me. I refer them in technical report.

[christos]

I am not an engineer but question the use of the NACA 66-009 airfoil. Although this airfoil has a very low drag coefficient in the very narrow laminar drag bucket it also has a poor lift to drag ratio. My understanding is that an airfoil with a better lift coefficient would allow the use of less wing( less drag ) and have better flight characteristics from cruse through stall. The NACA 66-009 would have a root thickness of approximately 0.117m or 4.5 in which would need a very strong spar at the root and have very little room for fuel. Also wouldn't the flaperons on such a severe stall airfoil cause an adverse yawl stall spin scenario?

Otherwise it should be a good motor glider and excuse my ignorance.

I used naca 66-009 only for vertical and horizontial stabilizer. I didn't publish main's wing airfoil. I don't answer in other question because i think it is on naca 66-009

[christos]

Stress forces resulting from a dynamic responseanalysis (for loads in flutter condition) in the LISA finite element program.

https://www.youtube.com/watch?v=BNAomwHgPbI

[christos]

Happy new year! Best wishes for 2019!
I start a more detailed technical report. Not only because I want to advertise my design but additionally because (I think) some people want to design and built their own planes. So this technical report (maybe) will be useful.
I like planes since I was a child and I want to build my own plane. My studies at university (i am a civil engineer) was useful throughout the design. It required to study structural analysis and it is highly recommended study finite element analysis for someone who wants to design a plane. You can design a plane with classic structural analysis and hand calculations but you need a finite element analysis software if you want to solve a sandwich structure and/or to run a flutter analysis. Theoretically, you can solve anything by hand calculations but you will spend a lot of time. It is not possible in the real world.
Also before you choose the software you have to choose structure materials. Because some software isn't solving laminate materials (if you want to build a composite aircraft).
There are a lot of software out there which you can use. From free open source to very expensive commercial like ansys.
I go with open source and low-cost commercial software because I don’t have enough money to buy expensive commercial software and I believe that open source is the best choice (personal opinion)
So I choose Lisa fea software for structural analysis, code aster for non-linear structural analysis, xfoil for airfoil analysis, VLM software for 3d simple analysis (avl or xflr5 aero vsp, or a cheap commercial like Hanley innovations) and OpenFOAM for computational fluid dynamics.
After that, I start to study regulations to make sure that I will design a good plane for me.
At the start, I dream to build a four-seater plane but I think that it is really uncommon to fly with 3 other people, also a four-seater is experimental and it is more expensive to own it, for these reasons I go with the ultralight. But because maybe in future I will need a four-seater, I design it as a four-seater. 2 seats for adults in the front area and 2 seats for children or light adults. Additionally, I plan to build a kit and USA is a very interesting country because it has a lot of excellent homebuilders. For this reason, I designed it as lsa, but strong enough to carry 2 extra children and light enough to fly in Europe as an ultralight. Also, I have to make a low time and easy to build kit, so a well and simple designed composite laminate structure, will be a good choice (maybe the best one).

[planecrazzzy]

I start a more detailed technical report. Not only because I want to advertise my design but additionally because (I think) some people want to design and built their own planes.
).


Advertise your Design ???

I would THINK you need a WORKING model...

THAT would advertise your design.

I see a lot of the 1%......(Thinking about it)

Where the rubber meets the road is BUILDING the plane... the part everybody has trouble with... 99%

There are NO two seat ultralights... You might start by reading WHAT IS AN ULTRALIGHT...

So far... I only see paper airplanes full of hot air
.
Gotta Fly...

I build planes and FLY them , You should try it.
When "I" look at a plane to BUILD...
I look for a proven design .
Kolb and Wittman are both in the Smithsonian Museum

[Sam Buchanan]

Advertise your Design ???

I would THINK you need a WORKING model...

THAT would advertise your design.

I see a lot of the 1%......(Thinking about it)

Where the rubber meets the road is BUILDING the plane... the part everybody has trouble with... 99%

There are NO two seat ultralights... You might start by reading WHAT IS AN ULTRALIGHT...

So far... I only see paper airplanes full of hot air
.
Gotta Fly...

I build planes and FLY them , You should try it.
When "I" look at a plane to BUILD...
I look for a proven design .
Kolb and Wittman are both in the Smithsonian Museum

We need to be aware of language context and world-wide regulations before we get too critical of somebody's posts. Christo is in Greece and I suspect English is not his native language. Also, the definition of 'ultralight' varies depending on the national regs under which it flies. The European definition of ultralight is considerably different from the USA.

[christos]

I would like to make clear that when I tell "ultralight" I refer to European ultralight. I told that "fly an ultralight in Europe".
About everything else, I am an engineer. I design it and I will start to build the prototype one of the following months.

I like to write a complete report about design. So when it will be ready everyone will be able to know about r&d of the aircraft.

## thank you Mr Sam.

[planecrazzzy]

We need to be aware of language context and world-wide regulations before we get too critical of somebody's posts. Christo is in Greece and I suspect English is not his native language. Also, the definition of 'ultralight' varies depending on the national regs under which it flies. The European definition of ultralight is considerably different from the USA.

Oh... He seemed to tie it together with LSA... Sorry , Scratch my comment...
.
.
Gotta Fly...
.
Here's some data like yours on a W-10

[christos]

Oh... He seemed to tie it together with LSA... Sorry , Scratch my comment...
.
.
Gotta Fly...
.
Here's some data like yours on a W-10

interesting

[christos]

Good evening my friends!
The second part of the design:
Now you know what do you want and you are ready to start the computational part of the design.
1) Select a good airfoil for your operation goals. It is very important. Because if you want a stol aircraft you have to go with a thick airfoil with good lift characteristics, if you want an aerobatic, you have to go with a stall stable airfoil etc. I want a fast long-range traveller, so I need an efficiency airfoil.
For this reason, I select a natural laminar flow airfoil and I developed a simple low operation energy boundary layer controller. It isn’t something new but isn’t common in small planes. But thanks to OpenFoam I develop one for my application. It is a vacuum boundary layer controller and my airfoil will be 85% laminar flow in the upper surface. It will be a simple but very important for aircraft’s efficiency mechanism. It needs only 7 amp and 12 volts. It is small enough to operate in a Rotax version (I am planning to buy one to test the plane). I design it around Rotax engines (rather than I prefer Subaru for a lot of reasons) because it has to operate well with an aeronautical engine if I want to make a kit from it.
Also, I design a cruise flap, but it wasn’t possible to use it with a slotted flap. The slotted flap will reduce the wing’s area, but it becomes too complex to a kit plane. Finally, I choose flaperons. It will operate as ailerons, cruise flap and flap at the same time. It isn’t something new, a lot of LSA and ultralight has flaperons. Some of them for the same reason.

Now you have the first 3d model of your plane.

2) Run a simple vortex lattice method analysis of your aircraft. Make sure that it is good enough for your goals and make a stability analysis. You don’t know exactly centre of gravity, but you will check stability again after you finish finite element analysis of the aircraft.
3) Make your 3d mesh model, choose loads and run your analysis. It seems easy but it is one of the most important parts of your design. Make a good grid to make sure that your results are accurate. Study about your construction materials carefully etc.
4) Run a stability analysis. Now you know the centre of gravity of your plane.
5) Choose computational fluid dynamic software to solve your plane. Vortex lattice method software is good but you have to run it in a really CFD software if you want to take accurate results about stall behaviour etc. There is a lot of software, I go with OpenFoam because it is open source and it is maybe the most powerful CFD software. Keep in your mind that you will need a really good pc. I run complex models and wasn’t possible to run them on a pc and I bought computing hours. It is a good choice.
6) Run a flutter analysis.
7) Run an elasto-plastic analysis (collision)
8) You are ready

**I will post screenshots from software

Thank you!

[planecrazzzy]

I'm guessing 6) is Flutter ???
.
Gotta Fly...

PS I see you fixed it... I can't delete this post.

[christos]

I'm guessing 6) is Flutter ???
.
Gotta Fly...

Yes my friend. I make a mistake, I am sorry about it.
Thank you very much for the comment and for your interest! :-)

[christos]

Hello, as i promised i make some screenshots of Lisa software. It will make more clear how i make finite element analysis.
If you go with Lisa, you can choose laminate material from the library.
You have to set parameters before you run an analysis. This is maybe the most important part of your design. You have to be sure about boundaries before you run an analysis.



7684
In this pic, you can see Lisa's laminate model. You can set both matrix and fiber parameters.


7685
In this pic, you can see the model's finite elements.


7686
In this pic, you can see another one Lisa's laminate model. Both are highly accurate models.


7687
In this pic, you can see the unidirectional carbon tube model.


7688
In this pic, you can see results in photorealistic rendering.


7689
In this pic, you can see the results' table.

[Matt Gonitzke]

"Highly accurate models"...okay. How are you validating them? How do you know they are "Highly Accurate?" From what I've seen in your thread here so far, you are leaning heavily (entirely?) on CFD and FEM analysis, which are dangerous to rely on without any validation.

[christos]

"Highly accurate models"...okay. How are you validating them? How do you know they are "Highly Accurate?" From what I've seen in your thread here so far, you are leaning heavily (entirely?) on CFD and FEM analysis, which are dangerous to rely on without any validation.

Dear Mr Matt,
Very good question. I ran a lot of real-world models in my PC and results was getting close to experimental.

[christos]

It's a long time since my last post.
The month was too busy. I had a lot of technicals problem with the dam's rebuild. Finally, I solve all of them but it wasn't easy. Now its' vertical slide gate operates smooth and soon will be ready to work the radial overflow gate also.

About the aircraft's project, i made some 3d drawings and i will start to build it. A high experienced composite builder here in Greece will make moulds and the first plane. Of course, i will help him, not only to reduce cost but also because i like it.

I will keep notice and photos from the build and i will share it with you, and i hope that you will enjoy it.

I need a little time of course because i have to solve some technical problems. For example, I have to measure other similar aircraft's cockpits and compare with my own to make sure that it will be comfortable enough. I have to make a research on the vacuum suction's construction because i want to make sure that it will be easy and comfortable to use for the pilot etc

Some 3d views of the aircraft. Additionally a drag polar with and without suction, you can see the benefit in drag. I hope that you will like it.

I will post tomorrow or day after tomorrow some magnitude pic with and without suction to make more clean the suction's benefit in the boundary layer.
7743
7744
7745
7746
7747
7748
7749
7750

[christos]

Some analysis' software screenshots (OpenFOAM). You can see the boundary layer benefits.
Also, i calculated the cost for a complete aircraft and i believe that it is affordable enough.

Best regards

7788
pic 1: blc off
7789
pic 2: blc on