FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1943
1943 - 1578.PDF
636 FLIGHT JUNE 17TH, 1943 POST-WAR TRANSPORT AIRCRAFT wing loading must not be more than about 72 if the machine is to comply with the American regulations. Except for twin-engine aircraft with a take-off power loading in excess of 14, this restriction is less severe than the restriction that the product of power loading and wing loading shall not be in excess of 300, which has been accepted as a rough criterion of margin of power in most of the preceding analyses of costs. The product of wing loading and power loading is some- what less satisfactory as a criterion of distance required for take-off when one engine fails during the take-off run than it is in gauging take-off distance with full power. It still serves the purpose to a fair degree of approximation, however; and in Fig. 20 the minimum length of take-off runway likely to be required under the present American regulations is plotted against the value of the product of wing loading and take-off power loading for twin-engine and four-engine aircraft. On the same chart there are included curves of the maximum power loading and mini- mum wing loading with which the several values of the product of wing loading and power loading can be realised without being liable to fall below the rate of climb with one engine inoperative that is required by the American regulations. 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 operat- ing conditions, too far? Or not yet far enough? Cer- tainly the new code is far more complex than the old. In 10,39 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 4J pages. Yet it seems impracticable- to secure a suffi- ciently 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- — I&TAN SO •£ r k\\ 4. / I f i, * ^ A — FIG 20 <•/ 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 determina- tion 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 con- sideration. * 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. Com- bining 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 full- power rate of climb by about "6ooft. per minute in a four- engine 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, t» 80 m.p.h. 1 will not dwell on that, beyond saying that it becomes critical only for four-engine aircraft with a relatively low power loading. More Exact Specifications The regulatory specification of flying qualities, and ^especially of stalling characteristics, is closely related to the regulation of performance. American ideas on that subject, too, -have undergone rapid development in the past few years, in the direction of making specifications more exact, of increasing the use of numerically determin- ' able standards, and of reducing the emphasis on dynamic stability requirements and replacing them with static stability criteria. It will be a problem of post-war planning to discover how far it may be possible to secure international uniformity in sueh matters as these. Obviously it is intrinsically desir- able that airworthiness standards should be common to all the air- craft - manufacturing and aircraft-operating countries of the world. Agreement on such matters will enor- mously facilitate inter- national trade in air-. craft and international air commerce. Regulatory authori-; ties in all countries will\ have to face in future the question of the rigour with which the standards developed primarily for services carrying large num- bers of passengers over fairly long distances should be maintained s K z JJO 316 \ —_n i _.J_ A.~——\ I / t... J.._ I \- r ENDI \ \ MONTHS MG 5/5/43 ! tMO I93» »32 t93« 1935 IS36 191 1958 .939 »*C American passenger safety record. port operations with necessarily light loads.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
