74 AEROPLANE PERFORMANCE CALCULATIONS 



should succeed in getting off the water in a calm is simply that 

 the P T curve has to lie above the P w curve all along. 



It will always be found that there is a pronounced hump on 

 the P w curve, which may cut into the P T curve : if this happens 

 the machine will not get off in a calm. In fact, it will be found 

 that a seaplane which has enough power to get off in a calm 

 always has quite a respectable margin of power for climbing, 

 once it is in the air. 



