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Will a plane traveling faster glide farther than a plane traveling slower once the engines shut down?

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Aerodynamics

All other things being equal, if there was complete engine failure in a passenger jet, would a plane traveling 500 mph glide farther than a plane traveling 400 mph?

There is logic to assuming the greater momentum of the 500 mph plane would carry it farther.

However optimum glide is affected by speed, and too much speed has a negative effect on overall distance.  Since the 600 mph plane has to spend more time slowing down to optimum glide speed, I guess there is some possibility that the slower flying plane would have a longer glide distance.

What say you, oh wise internet. 

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2 Answers



  1. Bob Watson on Apr 11, 2014

    Yes, the faster plane will go further.

    After the engines stop the only sources of energy available to the plane will be kinetic (momentum) and potential (altitude). If the two planes lose their power at the same spot at the same time, the faster one will have more kinetic energy enabling it to hold altitude (preserving its potential energy) longer. As it holds altitude while losing kinetic energy (slowing down), it’ll eventually reach a speed at which going slower (or faster) will increase drag (L/Dmax) and so you’ll want to keep that speed until you land going faster or slower than that speed will cause a steeper descent (with a lower or higher pitch attitude accordingly). If both planes are the same, this glide angle and speed will be the same, so the descent angle will be the same for each, but the faster plane will start descending after traveling further than the slower one.

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  2. Lucas on Apr 12, 2014

    Keep in mind though, that if the speed is faster than Best Glide Speed and is maintained through the glide than the distance travelled will become less because of the exponential increase in induced drag.
    If you are faster than Best Glide Speed you should immediately pitch for Best glide and this will cause you to gain altitude which in turn will give you more distance.
    If the higher speed is maintained than you will loose altitude faster to maintain it and travel a shorter distance.

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