53

Same reason gliders keep their wings waxed. It wasn't the camo per se, it was the dull matte field-applied paint finish that included all sorts of imperfections, and to a small degree, the weight of the paint vs natural finish. At a microscopic level, the surface of the matte finish was much rougher than a gloss or unpainted metal surface. The ...


25

If you can forgive my limited Paint skills: It's the variable/constant speed that makes the difference. Weight changes endurance (time to ground) and not range (distance to ground) if speed is adjusted to match the new weight. Weight changes the speed for best L/D, but does not ever change the best L/D ratio (and thus best range) For gliders (which are ...


18

It's primarily all about matte vs glossy finish. Normally a camo paint scheme would not be finished in a glossy finish as this might flash in the sunlight. A matte finish is rougher and thus has more air resistance than a glossy finish. The roughness is on a scale that is much larger than microscopic, but not obvious to the naked eye.


14

Green Dot (GD) speed is a term used by Airbus. It is named after the symbol on the speed tape. It refers to the speed that results in the best climb gradient in case of an engine failure, but it is close the speed resulting in best L/D ratio with all engines operating. Airbus defines it as follows: Definition GD speed is the engine-out operating ...


8

It's an engine testbed aircraft. In this particular picture, the tested engine is probably one of the PW1X00G series (mainly used by Airbus A220, Airbus A320neo, Embraer E-Jets E2, Irkut MC-21, Mitsubishi SpaceJet) and the aircraft is one of two Boeing 747SP testbed aircraft owned by PW. Engine testbed aircraft test the engines in-flight, with parameters ...


5

It means the profile is based on descending at 0.78 Mach until the IAS increases to 280 knots, at which point that speed is maintained to 10,000', at which point the aircraft slows to 250 knots for the remainder of the descent until it's time to slow & configure for landing. That 0.78/280/250 is a very standard profile for descent planning in the 737, ...


5

Read the POH - it will show the conditions the speed was measured under. Cruise, 75% Power at 8500 Feet. . . . . . . . . . . . . . . . . . 122 KNOTS NOTE *Speed performance is shown for an airplane equipped with speed fairings which increase the speeds by approximately 2 knots. There is a corresponding difference in range, while all ...


4

First I have to say that XFOIL is not the right tool for such a high Mach number. Professor Drela has written ISES to address the shortcomings of XFOIL at transsonic speed. Next, the critical Mach number is well defined as $$c_{p_{crit}} = \frac{2}{\gamma\cdot Ma_{\infty}^2}\cdot\left(\left(\frac{2}{\gamma+1} + \frac{\gamma-1}{\gamma+1}\cdot Ma_{\infty}^2\...


3

The FAI's photo of Daedalus shows its height above the sea to be considerably more than its wingspan, putting it out of ground effect. (Wikipedia says that most of the flight was 15 to 30 feet high, well within ground effect because the wingspan was 112 feet.) I couldn't find any official FAI record for height achieved by a human-powered aircraft, though.


3

The 737 and A320 are certified under Part 25, and they meet the certification requirement in 14 CFR § 25.121. With the gear retracted and one engine out: ... The steady gradient of climb may not be less than 2.4 percent for two-engine airplanes ... Aircraft Flight Manuals (AFMs) don't typically include the all-engines gradients of climb as noted in AC ...


2

Of course not. The pilot needs to be able to command the maximum turn capability of the aircraft when it is necessary, for, among other things, to defend against a missile that has been launched at him/her, to maneuver the aircraft into a weapons launch envelope, or to slow the adversary line-of-sight-rate for a high angle-off (heading crossing angle) gun ...


2

Why does an airliner have a shallow descent when heavier, opposite to gliders with ballast? Actually, gliders share this characteristic with airliners, if we are talking about flight at some given high airspeed that is well above the airspeed for the best L/D ratio. First a few general observations about gliding flight, based on something borrowed from ...


2

It sounds like you're looking for a Supercritical section, so this NASA report on Supercritical Airfoils may be of use.


1

Can jet fighters be made to be 2 or 3 times bigger than they are today? Yes. Consider the Tupolev Tu-28 (or Tu-128) "Fiddler" interceptor. Also the Lockheed YF-12A.


1

In addition to all the good content in all the other good answers, one more point should be made: when the airmass is moving horizontally and/ or vertically, the glide ratio over the ground is different than the glide ratio through the airmass, and therefore the glide ratio over the ground is different than the L/D ratio. When gliding into a headwind, the ...


1

It's not a huge problem if the wind is not too strong and there is plenty of runway. Ignore perceptions of groundspeed and land normally according to airspeed. I've conducted some experiments that actually tend to result in smoother landings with a tailwind component than with a headwind component; the wind gradient (which tends to increase or maintain the ...


1

The major problem with landing light aircraft, especially tail draggers with no steerable nose wheel,and tailwind component,is the lack of control when roll-out speed drops to that component or below. In fact,below it,control actions reverse! This is often more important than the higher touch-down speed, due to uncontrollable lateral departure from the ...


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