Behaviour of a Ground Effect Machine 



to a large extent proportional to the exciting force and moment for heave and 

 pitch respectively. So the largest pitch amplitudes were expected in waves of 

 about the air cushion length. The experiments showed that the largest ampli- 

 tudes occurred when the waves were slightly longer. 



With regard to the wave direction, it was found that pitch, resistance and 

 accelerations were the largest in head seas as appears from Fig. 11. Conceiv- 

 ably, the roll motion, lateral force and yawing moment were maximum in beam 

 seas. The worst condition for the model appeared therelore to be a bow sea 



HEAVE 

 DOUBLE AMPUTUDE 



ALL WAVE LENGTHS 



^^_^z5a_j/L, 



-MEAN RISE HEIGHT 



MOMENT OF YAW 

 DOUBLE AMPLITUDE 



FOR ALL WAVE LENGTHS 



PITCH 

 DOUBLE AMPLITUDE 



MEAN TRIM ANGLE 



FOR ALL WAVE ' LENGTHS 



LATERAL FORCE 

 DOUBLE AMPLITUDE 



ACCELERATION FORWARD 



-WAVE DIRECTION IN DEGREES 



-WAVE DIRECTION IN DEGREES 



Fig. 11 - Effect of wave direction at 30 knots, wave height 2 feet, 

 2580 fan revolutions per minute 



707 



