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Aviation History
1961
1961 - 0178.PDF
178 FLIGHT, 10 February \% except the USSR, Red China and countries which are not member'sof ICAO.) This index, however, has a serious deficiency in that accider.tsin which, say, one person is killed do not affect the index any more than accidents in which 50 or 100 people lose their lives.Furthermore, serious accidents in which all the passengers escape —perhaps miraculously—are not reflected at all. Neverthek s.from the passengers' point of view, this index is probably m •« tangible thin any other, and some comparative figures are there-fore given later in this article. If we use as an index "accidents per 100,000 hours" we runinto the problem of quite minor accidents being treated in she same manner as total losses; furthermore, on a worldwide bs isit is difficult, although perhaps not impossible, to keep track of all accidents which occur. A system based on aircraft destroyed per 100,000 flying hoursis more valuable, since it cuts out all the trifling accidents. Also, it is a relatively straightforward matter to keep track of total lossesonly. This index is particularly useful when comparing the acci- dent experience of different airlines or the record of different typesof aircraft, and is one way of comparing the jet and non-jet air- liners. Unfortunately, no statistics are published on this basis,so far as is known, but the necessary raw material is available and has enabled some figures to be worked out. These are given later. NOW A MILLIONJET HOURS BY ALAN E. SMITH GradRAeS SOME time this month, perhaps this week, the Western World's fivejet airliners will have flown one million hours. This article examines the safety record and suggests some new methods of assessment.T HE five types of jet airliner in regular service with thewestern world have now amassed a total of approximately one million flying hours. Whilst this amount of experienceis Still relatively small compared, say, with the nearly nine million hours flown on the world's scheduled services (excluding Russiaand Communist China) last year, it is nevertheless perhaps suffi- cient to allow a quick first appraisal of the jets from an accidentpoint of view. But on what basis can the accident records of different types of aircraft be compared? The commonly quoted accident statistics, such as passengerfatalities per hundred million passenger miles flown, and pas- senger miles per passenger fatality, do not provide a particularlysuitable method of comparing the accident experience of jet aircraft with that of the conventional piston-engined or turboprop-poweredairliner. This is because the higher productivity of the jets is reflected in these indices, a change in which may not be due toa change in the frequency with which accidents are occurring. In order to establish this factor, accidents can be expressed withrespect to flying hours. TABLE 1: JET FLYING HOURS Estimated as at February 10, 1961 Figures rounded off Boeing 707 DC-8Comet 4 Caravelle ... Convair 880 550,000 215,000155,000 110,000 6,000 1,O36,OOOhr An advantage of using statistics based on hours flown is thatflying hours for both airlines and aircraft types are relatively easy to obtain. Nearly all the transport aircraft manufacturers releasefrom time to time the total flying hours for the types they have produced, whilst the total hours flown during each year by indi-vidual airlines can be obtained from IATA and ICAO published material. The only hourly based statistic produced by ICAO is"Fatal accidents per 100,000 aircraft hours flown." (This relates to passenger fatalities on scheduled services on a worldwide basis It can be argued that, on this basis of comparison, the short-range aircraft is at a disadvantage compared with the long-range type; since it will make a greater number of take-offs and landings,a higher accident rate per hundred thousand hours might reasonably be expected. This criticism may well be justified,and an index based on total losses or serious accidents "per sortie" might clarify this point. Unfortunately, however, the necessaryfacts and figures are not at present available. There is then, no perfect, all-embracing way of expressingaccident statistics. At least several indices are required to give overall trends, and the limitation of each system has to beunderstood and accepted. TABLE 2: JET AIRLINER ACCIDENTS INVOLVING PASSENGER FATALITIES Date 27. 8.59 19. 1.60 19. 5.60 16.12.60 Operator and Aircraft Aerolineas Argentina* Comet 4 SAS Caravelle Air Algerie Caravelle United Air Lines DC-8 Location Nr. Asuncion, Poraguay Nr. Essenborga Airport, Ankara Nr. Orly, Paris New York Passenger Fatalities 1 35 1 77 Circum- stances Approach Hit hill Collision Collision To turn now to the comparative figures. For the three-yearperiod 1956, 1957 and 1958 (almost entirely non-jet) the ICAO figure for fatal (passenger) accidents per 100,000hr was 0.34, 0.36and 0.35, so there was on average one fatal accident about every 300,000hr. Although, of course, pure chance can cause unpre-dictable variations in statistical trends, it is perhaps reasonable from the above figures to predict that in the million jet hoursflown so far, there might be, perhaps, three or four fatal accidents involving passengers. There have in fact been four, although (asTable 2 shows) only two of these accidents involved heavy loss of life. On this basis of comparison, therefore, there is no evidenceso far to suggest that the jets will turn out to be any different from the conventional airliners—particularly as not one of theaccidents can be attributed to a fault in the aircraft. As stated earlier, there are no worldwide published figures oftotal losses related to flying hours, but some figures have been arrived at by compiling lists of total losses from various sourcesand relating them to the hours published by IATA and ICAO. An examination of all the IATA carriers during the years 19:6,
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