IV. Basic Considerations 



The obvious and important factors to be considered in the design of a high-speed 

 water-based aircraft in the sense defined are listed in Figure 1. What is not so obvious 

 and depends greatly on current trends is their relative importance with regard to the 

 basic compromises that must be made in procurement specifications and major design 

 decisions. 



Flight 



In the first place, there can be little or no concession to established aerodynamic 

 principles that provide favorable drag levels near and above the speed of sound in 

 relation to currently available thrust levels. Once the desired speed is achieved, range 

 and payload remain critical so that various factors in the range equation must be 

 carefully balanced to attain useful mission radii. The characteristically low lift-drag 

 ratios at supersonic speeds and the large adverse effects of small weight increases on 

 range demand a great deal of design ingenuity to obtain useful performance, and more 

 than ever before place flight considerations first. 



Take-Off and Landing 



The wing geometries and areas associated with high-speed flight have led to 

 very high minimum flight speeds and the maximum water speeds with which the hydro- 

 dynamicist must deal. Contemporary landplanes are operated at runway speeds approch- 

 ing 250 knots, and unless STOL or VTOL techniques can be applied their water-based 

 counterparts will be required to take-off and land at twice or three times the water 

 speeds of post-war propeller-driven seaplanes. The questions of whether such speeds 



<\. FLIGHT 



SPEED 



RANGE AND PAYLOAD 



B. TAKE-OFF AND LANDING 



SPRAY CLEARANCES 

 STABILITY AND CONTROL 

 TAKE-OFF PERFORMANCE 

 ROUGH-WATER CAPABILITIES 



C. MANEUVERING AND HANDLING 



Figure J. Basic considerations. 



184 



