|Quoting DfwRevolution (Reply 19):|
Do you know how an airplane flies? Ã‚Â Ã‚Â
The friction between the landing gear and runway is not the reaction that accelerates the airplane. The engines of an airplane are reacting with the surrounding air to apply force directly to the airframe. Wheels are just a convenient means to allow the aircraft to translate while on the ground. The friction forces involved with the landing gear are not sufficient to prevent the aircraft from accelerating if the conditions of the conveyor belt follow the guidelines of the experiment.
The aircraft accelerates, air flows over the wing, the airplane takes off. To quote a good friend of mine: the conveyor is moot
I assume they will use a GA
aircraft. Up until a certain (very low) airspeed, rolling resistance will be the main force to overcome. If you don't believe me, try a soft-field takeoff... you'll understand the impact of rolling resistance in getting airborne. At a certain point aerodynamic drag takes over but that should be pretty close to the point where lift starts and once that happens rolling resistance quickly gets negligible as the weight is lifted off the landing gear. There is, of course, also the impact of ground effect to consider, which is something we try to use in a soft-field takeoff, to get the plane out of the muck and accelerating quickly to flying speed
Bottom line though, the conveyor won't have any significant impact.
They may, however, want to have a look at the tire rotational speed limit on the sidewall if they want to avoid having a nasty (and expensive) experience, which will include pi$$ing off the owner of the aircraft.
|Quoting SKA380 (Reply 42):|
Anyone who knows a little about aerodynamics knows that an aircraft needs airflow over its wings to create positive lift.
So if we here are talking about (sorry, i haven't seen the previous discussion thread on this) a regular aircraft on a conveyor belt, doing basically 0 knots GROUND speed, then NO, the aircraft will not have liftoff..
I can make, oh say a Piper Cub, take off with zero knots ground speed.
It's air speed that matters, not ground speed. The Cub has a 33 knot stall speed. Turn it into a wind greater than 33 knots, cut it loose, and you'll be airborne with no forward ground speed (hint: for some reason, people like to tie down their aircraft when not flying). I have seen pilots amuse themselves in a Cub by flying with negative groundspeed. That is, airspeed was forward, but the wind strong enough that the plane moved backwards over the ground. The stronger the wind (assuming it's straight down the runway... if not, at some point it overcomes the aircraft-and pilot's-crosswind limitation), then the lower the ground speed needed for takeoff, including up to theoretical zero or negative. Wouldn't want to try that in my plane though: clean stall is 63 knots. If the wind is that strong, I should be at home waiting for the roof to blow off, not out flying!
However, in most cases you need forward ground speed to achieve enough airspeed to take off.
Now for landing the 747... in a simulator... coached... maybe. Otherwise, forget it. I'm sure even a good GA
pilot would be severely challenged. First of all, managing the momentum generated by 500,000 lbs of aircraft isn't the same as dealing with the momentum of 2450 lbs of aircraft (MGTOW of my bird). Secondly, sitting two stories up, the sight picture at the flare will be all wrong, you need to interpret radar altimeter readings, etc. Like I said, with coaching, maybe... but otherwise, a prang is likely.