Murthy 



DISCUSSION 



Lawrence J. Doctors 



University of New South Wales 

 Sydney a Australia 



I find this paper very interesting, because the response of 

 an aircushion vehicle to a seaway is an important factor in the opera- 

 tion of these craft. Violent motions are to be avoided from the points 

 of view of both the passengers, and of the craft structure, i. e. safety. 

 In addition, it is desirable to maintain a minimum operating speed, 

 which is not always possible in waves of a large amplitude. 



I would like to ask some questions about the analysis used by 

 the author. Firstly, I can see no place in the paper, where the fan 

 characteristics are involved. Surely, the interaction between fan pres- 

 sure and volume flow would affect the dynamics of the craft. In other 

 words, this is an additional parameter in the coupling between the 

 motion of the ACV and the response of the water surface. 



Secondly, one woujd expect the timewise varying air gap be- 

 tween the skirt hemline and the water to be an important factor. Has 

 this in fact been considered, for the air gap affects the pressure drop 

 under the skirt ? 



I am also interested in the way the pitch stability of the am- 

 phibious craft is modelled. For example, does the author compart- 

 ment the air cushion with a transverse skirt ? Incidentally, this would 

 introduce a nonlinearity under certain conditions. 



My final question is this : Has Dr. Murthy carried out any 

 numerical calculations, or does he consider that computer time would 

 be too excessive ? 



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