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Aviation History
1943
1943 - 1579.PDF
JUNE 17TH, 1943 FLIGHT 637 RATIO OF TRIPS COMPLETEO TO TRIPS SCHEDULED IN DOMESTIC AIR TRANSPORT OPERATION Ratio of trips completed to trips scheduled in domestic air carrier operation. I turn now to the problem of future airport size, which is intimately related to the questions of economy of opera- tion, of the prospective size and design characteristics of transport aircraft, and of the regulatory standards that are to be imposed, and to the degree of safety that is to ,be attainable. . Airport Size No matter how large airports may be made, one may confidently anticipate that there will come a time when some particular airport will not have been large enough for a particular emergency, and when a pilot will feel that if the runways had only given him a few hundred feet more in which to bring the aircraft to rest the crash would have been averted. Fig. 20 has shown how the length of runway that is profitably usable under existing American requirements with respect to the effects of an engine failure during take-ofi is primarily a function of wing loading. Within the range of wing loading of from 20 to 45 lb. per square foot, the lerfgth of runway required for getting off in accordance with the regulatory requirements, while carry- ing the largest power loading that is compatible with secur- ing the required climb with one engine inoperative, is approximately: L= 1,000+150 (W/S). The maximum usable length of runway ranges from a little over 3,000ft. with a 15 lb. wing loading to nearly 8,000ft. with a loading of 45 lb. per square foot. The distance so determined seems to be very nearly the same for twin-engine and four-engine aircraft. Assuming the use of highly efficient flaps, but without variable-area devices, the existing stalling-speed requirements may permit maximum wing loadings at the time of landing of approxi- mately 32 lb. per square foot for twin-engine and 38 lb. per square foot for four-engine aircraft. The take-off loading may be increased above that figure by the amount of fuel that is to be used in flight. With a given wing loading and span loading, the maximum power loading with which a rate of climb of 0.02 Vj^,, with one engine operative can be attained at a height of 5,000ft. should be about 20 per cent, greater than the maxi- mum power loading with which the condition relating to climb imme- diately after take-off can be met. That, in effect, is the nature of the benefit derived from assisted take-off or refuelling in flight. It RATIO OF MILEAGE FLOWN TO MILEASE SCHEDULEO IN AIR TRANSPORT Ratio of mileage flown to mileage schedule in air transport. makes it possible to eliminate from the aircraft the weight of a certain portion of the power-plant, that would other- wise be required to get the aircraft safely into the air and for no purpose thereafter. No discussion of air transport developments could be complete without some mention of the notable improve ments in the safety record that have been made in receni years, and of the means whereby the improvement may be continued. So far as the past is concerned, Fig. 21. which shows the passenger safety record of the airlines operating within the continental United States during the past 14 years, speaks for itself. I have departed from the common practice of using the number of passenger miles per passenger fatality as the criterion of safety, substituting the reciprocal of that ratio, since a function that gradually approaches zero lends itself more readily to graphical repre- sentation ihan does one that gradually approaches infinity. Tn appraising the chances of a further substantial reduc- tion and the means of attaining it, it is useful to consider the circumstances of the accidents of the recent past and to see how far they could have been averted by measures which may be standard practice in future. Obviously no examination on that basis can be conclusive; for the future will bring new problems, and may bring new troubles and causes of accidents for which nothing in the past has pre- pared us. Still it is true that accidents do repeat them- selves in general character, and present a recurrence of Common factors to a greater extent than is olten realised. In the past four years there have been 12 fatal accidents on airlines within the United States, in 430,000,000 miles ol flying. Seven of that number occurred while making approaches for landings. In two of the seven cases the pilots were confused about their location; in two more they were landing on comparatively short Tunways; in two cases the pilots were either approaching the field or circling it under a low ceiling; and in the final instance there appears to have been an error in setting the altimeter, with resultant collision with the ground during an approach at night. The Human Factor In two instances, including one of the seven cases of landing approach previously mentioned, the pilots appear to have made errors, despite generally favourable con- ditions, which should have been wholly unnecessary. In one of the four remaining cases, a transport was run down from behind by another aircraft. In only one instance in the four years does any mechanical failure of airframe, engine, or any accessory appear to have played a part. One of the accidents was attributed, although somewhat speculatively, to lightning, and one remains a complete mystery. In only two of the twelve cases was ice on the aircraft involved, and in neither of those instances was the icing so severe as to have made the accident inevitable if the airport conditions had been as good and the navigational aids as highly developed as we may reasonably •hope that they typically will be after the war. In no instance was there fire in the air. &ot a single fafal accident involved a break- down ot radio communication or the failure to understand a spoken message correctly; and it is a high tribute to the efficiency of the organisations controlling air traffic that no fatal accident in air trans- port has involved any error in traffic control. Air transport has had many ad- vantages over the older-established surface forms, bat it has laboured under the disadvantage of a sub- stantially greater liability to cancel- lation of schedule than characterises its slower competitors. Regularity, like safety, must be *examined in JUHC JULY «UC SEPT OCT NOV OEC.
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