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Interesting question. Are you suggesting a wind machine that is capable of
creating a wind that matches the conveyor? Let's start with no wind. The plane must achieve lift off speed relative to the stable air mass to take off. airspeed = Vlo Conveyor moving = - Plane motion relative to ground Conveyor moving = -xVlo (relative to ground) airspeed = Vlo = Plane motion relative ground + headwind = xVlo + 0Vlo; solve for x = 1 Wheels spinning = Plane motion - conveyor motion = xVlo - -x Vlo = 2 Vlo Plane will liftoff at an airspeed that matches its groundspeed of Vlo. The conveyor is moving backward also at Vlo. The wheels are spinning at twice that speed. Now with a headwind. The plane must still achieve lift off speed relative to the air mass which is now an accelerating headwind. airspeed = Vlo Conveyor moving = - Plane motion relative to ground Conveyor moving = -x Vlo (relative to ground) Headwind = Conveyor moving Headwind = - x Vlo (relative to ground) airspeed = Vlo = Plane motion relative ground - headwind = x Vlo + x Vlo; x = 1/2 Wheels spinning = Plane motion - conveyor motion = 1/2 Vlo - -1/2 Vlo = Vlo The plane will be able to lift off at 1/2 the ground speed than under normal circumstances. The wheels are spinning at twice that speed which is just Vlo. It would be feasible to construct both such a conveyor and the wind machine. Now with a tailwind. The plane must still achieve lift off speed relative to the air mass which is now an accelerating tailwind. airspeed = Vlo Conveyor moving = - Plane motion relative to ground Conveyor moving = -x Vlo Tailwind = - Converyor moving Tailwind = x Vlo (relative to ground) airspeed = Vlo = Plane motion relative ground - Tailwind = x Vlo - x Vlo; ******** No solution ******** With this simple formula, the plane will never take off but will continue to accelerate (until the wheels disintegrate) since the thrust of the engine is acting on the air mass which is accelerating as a tailwind. Very much the dog chasing his tail. Assumptions: As with most things in life, we need a point of reference. Almost any will do but I chose the ground upon which the conveyor belt is built and we are standing watching. It is from this reference that the conveyor belt's velocity (backwards) is derived. I arbitrarily chose the positive sign of velocity in the direction of the plane motion. -- ------------------------------- Travis "darthpup" wrote in message oups.com... Must consider the wind at time of experiment. If wind is same speed as conveyor then real problem?? |
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