Post-war Transport Aircraft
Post-war Transport Aircraft
Dr. Edward P. Warner's Wilbur Wright Memorial Lecture
From page 636 in FLIGHT June 17th, 1943: (Flight International Archive)
Loading Limitations
It appears that the necessary rate of climb can hardly be attained with a loading product of 500 in a twin-engine aircraft, for example, unless the wing loading is at least 50 lb. per square foot and the take-off power loading less than 10 lb. per horsepower.
Upon the assumptions used herein, the maximum wing loading that is allowable without undue increase in stalling speed becomes a limiting factor in seeking maximum economy of operation at speeds in excess of about 225 m ph. At speeds below that figure it is likely to be the take-off condition that is controlling.
Have we now carried elasticity in regulation, and the adaptation of regulatory requirements to particular operating conditions, too far? Or not yet far enough? Certainly the new code is far more complex than the old. In 1939 the specifications with respect to the landing and take-off performance of aircraft consumed only 16 lines of the American Civil Air Regulations. They now occupy 41/2 pages. Yet it seems impracticable to secure a sufficiently definite statement in less compass, and I believe that there are few if any of the American manufacturers or operators who would forgo the advantages of the flexi-bility of the new regulatory code in order to regain the simplicity of its predecessor.
I believe that we are on the right track in establishing correlation between the characteristics of the aircraft and the characterises of the route on which it is to be operated ; and I believe that we shall see much more of the same sort of thing.
In addition to the provisions relating to the determination of landing distance and take-off distance, the American regulations, unlike those drawn up under the I.C.A.N., provide for maximum limits on stalling speed. The general improvement in the smoothness and firmness of airport surfaces, and the steady increase in mechanical reliability and consequent decrease of the hazard of having to land elsewhere than on a regularly prepared airport surface, have diminished the direct importance of the speed at which the aircraft makes contact with the ground. The speed of approach to a landing, however, is still a serious consideration.
It seems to be the prevailing view among experienced airline pilots in the United States that they do not want to have to make approaches, under present conditions, at over 120 m.p.h. Good practice seems to require also that the speed maintained during the approach should be at least 40 per cent, in excess of the stalling speed. Combining the 120 m.p.h. with the 40 per cent, reserve indicates a stalling speed of 85 m.p.h., and that is the level at which American regulation currently sets the maximum allowable in the "approach condition."
The loss of one engine characteristically reduces the fullpower rate of climb by about "6ooft. per minute in a fourengine transport aircraft and 1,200ft. per minute in a twin-engine one.
There is a further limitation of maximum stalling speed in the landing condition, with full flap, to 80 m.p.h. I will not dwell on that, beyond saying that it becomes critical only for four-engine aircraft with a relatively low power loading.