GROUND PERFORMANCE 65 



M(V - v w g 



_ KV 2 - from (I) 



Equation (/) gives the required length of deck for landing on 

 a ship. 



From this we can get the length of run for landing on an 

 aerodrome in still air, by putting v w = o. 



We see that it leads to / = co ; that is to say, that if there 

 was no ground friction, the air resistance would never quite stop 

 the machine moving. We must therefore investigate the length 

 of landing run, taking account of friction. 



Landing on the Ground. We suppose that brakes on the 

 wheels, the friction of the tail skid, or even simply the friction 

 of the ordinary wheel axles, have the effect that the machine 

 can be considered to have a coefficient of friction p with the 

 ground. 



Let M be the mass of the machine in pounds. 



Let x be the distance in feet from the point of contact with 

 the ground. 



Let v be the landing speed in feet per second. This is either 

 the "slowest flying speed," which has been found on page 50, or 

 the " landing speed on glide," which has been found on page 35, 

 according to whether the pilot lands with engine on or off. 



Let / be the time in seconds after touching the ground. 



Let KV 2 be the total resistance of wings and body at the 

 altitude at which the machine runs on the ground in poundals at 

 speed V feet per second. 



Let / be the length of run in feet. 



Then the air-borne weight = 



5 



