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Landing distances

E=½mV2. So, the heavier the airplane, the more energy must be expended to get it stopped. Something about Newton's first law of motion - Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. The velocity is the big one because as it changes, it changes the energy needed to stop exponentially. And velocity on landing is effected by: The heavier the airplane, the faster it has to fly to create enough lift to counteract the weight (lift = weight in level flight) The headwinds make the groundspeed slower - slower landing velocities. If an airplane normally lands at 30 knots and it is flying into a 30 knot headwind, the landing roll would be zero. Aircraft carriers always want to be going into the wind so the velocity of the aircraft is reduced by the speed of the ship plus the speed of the wind. The higher an airplane flies, the higher its true airspeed for the same indicated airspeed. And it lands at about the same indicated airspeed (except for changes in weight). So higher field elevations causes faster velocities on landing - and longer landing rolls. Higher an outside temperatures, also cause higher true airspeeds and so temperatures are like higher elevations.

A couple of other factors effecting landing distances include: The higher you must be over the threshold of the runway (trees, power lines etc) also adds to the landing roll because you must descend that amount before landing and that is potential energy that has to be dissipated. One last thing I can think of that effects landing rolls is the condition of the runway surface. A wet runway can cause hydroplaning (9x?(Tire Pressure)=Hydroplaning Speed). Other factors are items like: dirt/mud, grass, slope, snow, ice etc.

 
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 Dick Fechter
(507) 775-7686
FPS@ 44RF.com)
139 13th St NE
Byron, MN 5592
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