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Aviation History
1969
1969 - 0117.PDF
H.IGHT Internotiona/, 16 January 1969 Air safety: a "Flight" special feature Jet safety TEN YEARS OF OPERATIONS ANALYSED By ALAN A. SMITH, C6i.g, AFRA.S Some 700 jet airliners were delivered to the Western World's airlines in 1968, bringing total deliveries to around 3,000. Jet flying hours during last year amounted to a record 7.6 million, an increase of 1.7 million over 1967, and equal to the total of jet hours flown during the first five-and-a-half years of jet operations starting in September 1958. Total jet hours rose to 31 million by the end of 1968. This article re-examines the jet accident record so far, with particular reference to last year's figures and their significance to future operations. DURING THE FIRST six MONTHS of 1968 jet airliner accidents occured at an unprecedented rate and with surprising regularity. By mid-year 11 jets had been written off and it looked as if the end of the year figures would be alarmingly high, with perhaps more than 20 total losses chalked up. Fortunately the second half of the year was better. Neverthe less, The number of total losses during the year amounted to 19. (This figure does not include the jet aircraft destroyed at Bei*ut on December 28 by an Israeli Commando Unit, and these are not included in the analysis which follows.) This is the highest number of jet total losses recorded in any calendar year, the previous highest being 15 in 1966. Twelve of these 19 write-offs occurred on passenger services and four on freight flights; two aircraft were destroyed by fire while they were undergoing maintenance; and one was damaged beyond repair when a piston-engined aircraft crashed into it on the ground. By the end of 1968 the overall total of jets written off had reached 98. So at first glance the 1968 jet record does not look encour aging. However, to obtain a clearer picture it is essential to relate the number of accidents to the amount of flying per formed. It seems to be generally recognised that there is no perfect way of expressing accident/safety statistics in air transportation but accident and fatality rates related to flying hours are generally more understandable than rates based on passenger-miles or aircraft miles. The analysis which follows is therefore based mainly on various accident rates per 100,000 flying hours. The relatively poor safety performance of jet airliners during their first three or four years of operations has been discussed in previous articles, and there is no need to comment on it in detail. But a quick look back is of interest because it high lights the point made by many safety experts, viz, that air transport safety must steadily improve each year if the number of accidents in future years is not to reach very high numbers. During the first 7.5 million hours flown by the jets (September 1958 to April 1964) there were 41 total losses. This implies that if there had been no improvement whatsoever in jet safety during the course of the last ten years there would have been around 40 total losses during the 7.5 million hours flown in 1968. From this quick glance it is clear that substantial pro gress in jet safety has been achieved during the last ten years. However, from the point of view of the future, it is the changes during the last few years which are significant. So it is pertinent to take a close look at the figures for these last few years. Jet total losses from all causes and under all circumstances are shown on a calendar-year basis for the last ten years in Fig 2. A rising trend is clearly discernible which gives cause for concern. If this trend continues, the number of total losses per year in the mid-1970s looks like reaching 40. Furthermore, as accidents are often spread unevenly throughout the year, there might well be periods of several months at a time in which jet total losses occur more frequently than one per week. If this were to happen, the public image of air safety might well be in jeopardy (not because jet safety was any less than it is now but because it appeared to be so). Total losses on passenger services are shown in Fig 3 and fatal accidents in Fig 4. A quick look at the block diagrams shows that, from the passengers' point of view, 1968 was much the same as 1967. Although the number of total losses on passenger services in 1968 was two higher than the previous year, the number of fatal accidents was one less. The number of passengers killed (353) was slightly higher than in 1967 (345) Fig I let airliner flying hours per year (millions) w IS F/g 2 Total losses, all circum stances. *The 1968 figure does not include the aircraft destroyed at Beirut by the Israelis on December 28 3 I 59 60 61 62 I I Fig 3 Total losses on revenue passenger services 59 eo Fig 4 Fatal (passenger) accidents 1 3 6 R~ 8 5 5 li ..?,. I « | 59 60 61 62 63 64 65 66 67 68
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