Friday, April 18, 2008

Airfoil documents

There is an interesting document on Selig's page:
http://www.ae.uiuc.edu/m-selig/uiuc_lsat/vol4/NREL-SR-500-34515.pdf.

It covers for example wind tunnel results for Wortmann FX63-137 at low Reynolds numbers.

Links to NASA tech papers about airfoils
Covers NLF 215F

Airfoils in dwg format

Airfoils in dwg format

Low cost UAV design

LINK: Low-cost Expendable UAV Final Report

Reynold's number calculator

http://aero.stanford.edu/StdAtm.html

Aircraft calculator web page

I found this:

http://anton.panchishin.com/docs/aircraftcalc.html

I am not sure how useful it is, but just for fun, enjoy.

Airspeed at sea level

I got interesting airspeed calculator Excel-sheet from Petri Flander. I have been calculating those things with my aircraft design program and by hand before, but it is surprisingly handy to see the effect of various flat plate drag areas and their effect to the airspeed. Great input for my program which I am writing the UI for with Qt right now, I may do also graphical output for these parameters, would be fun to have. This was actually also useful to reverse-engineer the flat plate drag areas of various aircrafts. For example I came up with 4,7 ft2 for Cirrus SR20 where Lancair ES (=same as Columbia 400) is 4,0, so Cirrus is a slightly less efficient than the Columbia (which is evident also from the performance numbers comparing SR22 and Columbia 400). Interesting is that I came up with 9 for C152, which is a terribly bad figure. And Zenair CH701 produced a number around 18 which was reverse-engineered from real performance numbers I have heard from a Zenair pilot. Couldn't get much worse than that. BD-5 has very low figure of 0,9 and Vmax probe is at 0,3 (these were obtained from elsewhere). A composite BD-5 with rear body laminar flow suction (with more laminar body shape as well) and some high tech airfoil like the NLF414F could be super-efficient. However, the issues with low Reynolds number from Vmax probe apply, it will have seriously dangerous stall charasteristics without modifications to the airfoil or wing.

Here is a copy paste from the sheet with flat plate drag areas from 0.3 (Vmax probe) to 4 (Lancair ES):


Aircraft speed, km/h Prop eff 0,85 Dens.ratio 1,000 $

Drag area
ft2 25 40 60 80 85 90 100 <- Total hp (Rotax 914)
4 148 173 198 218 223 227 235 127,053 kts
3,00 163 191 218 240 245 250 259 139,840 kts
2,40 176 205 235 259 264 269 279 150,639037908943 kts
2,30 178 208 238 262 268 273 283 152,791314948939 kts
2,20 181 211 242 266 272 277 287 155,07211859505 kts
2,12 183 214 245 270 275 280 290 156,998677308782 kts
2,10 184 215 246 270 276 281 291 157,495511877874 kts
2,00 187 218 250 275 281 286 296 160,077864487362 kts
1,90 190 222 254 280 285 291 301 162,838370152973 kts
1,80 193 226 259 285 291 296 307 165,799714672936 kts
1,70 197 230 264 290 296 302 313 168,988949701208 kts
1,60 201 235 269 296 302 308 319 172,438652178898 kts
1,50 205 240 275 303 309 315 326 176,188487565227 kts
1,40 210 246 281 310 316 322 334 180,28735558483 kts
1,30 215 252 288 317 324 330 342 184,796395706893 kts
1,20 221 259 296 326 333 339 351 189,793294797389 kts
1,10 228 266 305 336 342 349 361 195,378626469698 kts
1,00 235 275 315 346 353 360 373 201,685471089846 kts
0,90 243 285 326 359 366 373 386 208,894550582996 kts
0,88 245 287 328 361 369 376 389 210,46524527855 kts
0,50 296 346 396 436 445 454 470 254,107770484061 kts
0,31 347 406 465 512 522 532 551 298,003054739616 kts

Wednesday, April 16, 2008

Reference library

Here is list of some of the books I have:
Aerodynamics for Engineers
Fundamentals of Aerodynamics, by John Anderson
MODERN AIRCRAFT DESIGN, Volume 1 5th Edition, by Martin Hollmann.
MODERN AIRCRAFT DESIGN, Volume 2 4th Edition, by Martin Hollmann.
COMPOSITE AIRCRAFT DESIGN. REVISED 2003. By Dr. Hal Loken and Martin Hollmann.
MODERN AIRCRAFT DRAFTING by Eric and Martin Hollmann.
ADVANCED AIRCRAFT DESIGN by Martin Hollmann.
BRUCE CARMICHAEL'S PERSONAL AIRCRAFT DRAG REDUCTION

Aircraft Design : A Conceptual Approach
Daniel P. Raymer / Hardcover / 4th Ed. Published 2006
Theory of Flight
Richard Von Mises, Richard Von Mises
Aircraft Performance and Design
John D. Anderson / Hardcover / Published 1998
Sportplane Construction Techniques : A Builder's Handbook (Tony Bingelis Ser.))
Tony Bingelis; Paperback

Tuesday, April 15, 2008

Interesting aircraft design - LH10

This plane has some of the elements I have been thinking of an efficient aircraft to have:

http://www.lhaviation.com/site_frame/bases_marges/index.htm

Specs promise 200 kts with 100 hp. Lets see. The plane has already flown, but not yet tests that determine top speed.

According to my calculations, providing they are right, this is not that much out of place. This plane in fact, is pretty much like a two place Vmax Probe. If the airflow stays laminar in the fuselage and wings, the 200 kts might be doable. The relation of stall speed and top speed of the 3.77 projected for this plane is a reachable value. Very interesting to see how it performs and if it does not go 200 kts, why. According to what I have read and would estimate, the drag coefficient of the LH10 should be very small unless there is something wrong that causes the airflow to separate.

The view from the LH10 seems to be as spectacular than from a glider. Would be excellent aircraft for flying for fun.

The airfoil used on this aircraft is particularly interesting. Reasons:
- E.g. NLF414F produces very low drag and very high glide ratio, but not without restrictions - the area of usable Reynold's number is limited which limits the chord of the wing to a rather long one, and the wings of the LH10 would already be below that limit. They say that it is a wind turbine airfoil. I haven't tried simulating the wind turbine airfoils yet, it has not occurred to me that they could be actually be useful on aircraft. However, this seems to prove that this was wrong assumption, and they are in the UIUC database for a reason. Lots of airfoils to investigate...