English Deutsch Français Italiano Español Português 繁體中文 Bahasa Indonesia Tiếng Việt ภาษาไทย
All categories

The "flattest glide " question was good and got me thinking. I am not an engineer in the least so bear with any dumb questions. Efficiecny in an aircraft would ultimately be achieved with super long wings and an efficient,small engine (like Voyager). No good for Civilians. So a happy medium. Early Mooneys had longer wings.(I don't know now.) So at some point, length(lift) cripples speed yes? So a jet that has crazy propulsion hardly needs any wing and could be near ballistic, yes? It would gobble fuel though. So I guess my question is how much these factors affect modern civilian aircraft. (excepting big cor[porate jets that don't need much efficiency). Are todays prop/turbo-prop aircraft the perfect blend of lift and speed(speed being dictated by price meaning the higher the cost the faster someone needs to go). I ask because I know Avgas isn't too cheap...

2007-03-07 06:17:35 · 3 answers · asked by Anonymous in Cars & Transportation Aircraft

3 answers

A large set of questions. Aircraft are always mission specific and at best, a compromise of the various factors in aircraft design. Longer (straight) wings do increase drag, yes. But it's not that simple. Civilian aircraft are an example of the compromise I spoke of. By the way, the corporate jets DO strive for efficiency. Those people didn't get rich by throwing money away. It has been many years since civilian aircraft pretty much peaked in design principles. The changes we've seen in the last 50 years have been primarily materials, engines, and some direct steals from the military experience. All factors considered, today's aircraft do represent about as perfect a blend of lift and speed as present technology allows. The higher cost you speak of is mainly the jet engines and the ramp-up of aircraft structure to accommodate those engines and the speed they allow.

2007-03-07 08:33:54 · answer #1 · answered by Anonymous · 2 0

Everything in aerodynamics is a trade-off. There is no ideal, because of the variety of missions possible. Want long range or endurance? Then go with a long wing and high aspect ratio. Want speed? Then you need lots of power, and a short, swept wing.
Do speed + glide = efficiency? Not necessarily. The power required to go faster is not proportional. There is, for every airframe, an optimal cruise speed. Any gains over that speed require a LOT more power, and the faster you want to go, it requires that much more. There is an optimal speed for efficiency in cruise; there is an optimal speed for glide, where you are trading off altitude for distance. Again, everything here is a compromise, and it all depends on your goals.

2007-03-07 18:17:04 · answer #2 · answered by lowflyer1 5 · 0 1

No, efficiency is Lift/Drag, and for extension is the same with coefficients of lift and drag: efficiency= Cl/Cd
And when you glide you can move horizontally of a distance that is efficiency times the loss of altitude......so if your efficiency is 10, and you glide from an altitude of 1000m, you can travel about 10000m

Efficiency is not influenced only(and mainly) from the aspect ratio of the wing, but also by the kind of airfoil and the taper ratio(in general the planform shape).
*the wingspan is not important, only the aspect ratio: a R/C glider has a bigger aspect ratio than a fighter(F-16 for example) but a smaller wingspan, and the R/C glider will probably have a bigger efficiency.

2007-03-07 22:07:10 · answer #3 · answered by sparviero 6 · 0 0

fedest.com, questions and answers