of afterbody improves rough- water loads and motions (ref. [8]), but is detrimental with 

 regard to stability and resistance at high water speeds, as will be discussed later. 



Area rule application. — In addition to the features shown, the form may include 

 body indentations and bulges to minimize aerodynamic interference effects at transonic 

 speeds. Such distortions of the form will be located above the chines, and, except near 

 the after end, should not influence the hydrodynamic characteristics. In arriving at 

 the proper distribution of hull volume from area-rule considerations, the graphical 

 line-fairing methods of the naval architect have been employed to advantage to blend 

 the various aerodynamic and hydrodynamic features desired. Trial solutions in the 

 research laboratory for transonic and low supersonic configurations have indicated 

 the continued usefulness of the flying-boat hull for aircraft in this category. 



Hydro-Skis 



Probably the most significant of the post-war hydrodynamic developments has 

 been the so-called hydro-ski landing gear. This concept in its original form, stimu- 

 lated by the trend to jet power and the need to approach more closely an optimum 

 aerodynamic configuration, is illustrated in Figure 3. 



> 



BOTTOM VIEW 



FRONT VIEW 



LANDING W.L^ 5 ^^ 



PROFILE 



Figure 3. Typical high-speed fuselage with hydro-ski 



General. — Basically the hydro-ski is the hydrodynamic equivalent of the landing 

 wheel rather than the conventional seaplane float. As such, the floatation function is 

 dispensed with and it is deliberately made small enough for complete retraction in flight. 

 It then becomes comparable in weight and complexity with a wheel gear, and localizes 

 the landing loads near the airplane center of gravity. 



Stability. — Early investigations with free dynamic models indicated that simple 

 configurations like that shown may be expected to emerge (unport) stably, and to 

 operate under control of the pilot at high water speeds very much like a wheel gear. 

 They likewise may be made to land stably, and as the speed is reduced to the point 

 where the ski gear submerges, they settle gracefully into the water without uncom- 

 fortable motions or changes in course (refs. [9 to 11]). 



Resistance. — It was accepted at the start that the emergence water resistance 

 would be high, since the fuselage would preferably have a minimum of hydrodynamic 

 form and the necessary ski lift would be generated at a high angle of attack to make 



187 



