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Aviation History
1969
1969 - 0118.PDF
JET SAFETY but about 100 less than in 1966 (Fig 5). The trend of total losses on passenger services has been noticeably upward during the last five years; but. since the amount of jet flying increases each year (Fig 1), a true assessment of 1968 and prospects for the future can only be Obtained by considering the 1968 accident rates per 100,000 flying hours in relation to earlier years. Before discussing these rates a few explanatory remarks are necessary. i"' 345 353 59 60 61 62 63 64 65 66 67 fig 5 Passenger fatalities As mentioned earlier, three of last year's total losses occurred on the ground whilst the aircraft were not in operation. These accidents have therefore been excluded when calculating the total loss rate per 100,000 flying hours, and two previous "ground" total losses in earlier years have likewise not been counted. The total loss rate shown in Fig 6 might therefore be described as an "operational" total loss rate. On this basis of measurement, last year turns out to be almost the same as 1967. Both years had an operational total- loss rate of almost exactly 0.2 per 100,000 hours. Compared with 1966, in which the rate was 0.34, the results appears good; but, as the graph shows, 1966 was a comparatively bad year. Furthermore, the 1967 and 1968 figures are only very slightly below the 1964 and 1965 figures (0.21 and 0.22 respec tively) and there is no obvious sign of a downward trend during the last five years. The "operational" total loss rate for the last five years combined works out at 0.23 per 100.000 hours (i.e., one write-off per 430,000 hours). The total loss rate on revenue passenger services is shown in Fig 7. No obvious downward trend is noticeable during the last few years, and 1968 is not appreciably better than the Fig 6 Operational total-loss o-a rote per I00,000hr 0-8 0-7 0« 04 M M 0-1 /I / 1 / 1 4 » \ 1 \ *s. * A V J N V-* v- last four years with the exception of 1966. This graph is relevant because it depicts the "potential" fatal accident rate. Fortunately, not all total losses on passenger services involve fatalities; but such accidents are clearly of public concern and should therefore be recorded. At this point it is appropriate to point out that one of the accidents recorded in this category last year has subsequently turned out to be fatal (one passenger died several days after the accident as a result of it). The 1967 fatal-accident rate has therefore been amended accordingly and the new figure is shown in Fig 8. The figures for some earlier years have also been slightly adjusted, since jet flying hours in certain years are now known more accurately. As in previous articles, a fatal accident is defined as an accident in which a passenger is killed as a result of an aircraft crashing. The occasional turbulence accidents in which the aircraft suffers no damage but in which a passenger is unfortunately killed are therefore excluded. FLIGHT International, 16 January 1969 The fatal accident rate in recent years has clearly been a great deal better than during the first few years of jet opera tions (Fig 8) but the trend in recent years has not been an improving one. The rate of 0.12 fatal accidents per 100,000 hours for 1968 is much better than the rate for the three previous years, but there is no indication of a general down ward trend in recent years. However, since the amount of flying each year is increasing, it could be argued that the rate of 0.12 for 1968 is much more of an achievement than the similar figure in 1964, when only 2.8 million hours were flown compared to the 7.6 million flown last year. In view of this, the 30 million jet hours flown up to the end of November 1968 have been broken down into ten 3.000,000-hour periods and the various accident rates calculated and plotted in order to see how the accident rates are changing in relation to total flying time. The results of this analysis are discussed in later paragraphs. The inadequacy of the fatal accident rate on its own as an air safety indicator has been mentioned by many safety experts and this point is highlighted by the change in last year's fatal-accident rate as the result of a passenger dying some days after the accident. The fatal-accident rate provides a good indication of the frequency at which major accidents- are occurring, but it does not register how fatal they are. (This point may be particularly pertinent during the next few years in view of the forthcoming introduction of the large- capacity, wide-bodied jets.) This raises the all-important qties- Fig 7 Total-loss rote per 100,000 hr on revenue passenger services 0-7 0-6 0-5 0-4 0-3 0-2 o-i r A '\ i * i \ i \ ' V^ —i i i t i i—t i—i tion of the passenger fatality rate per 100,000 hours in recent years (Fig 9). From this angle 1968 was a comparatively good year, the rate of slightly less than five fatalities per 100,000 hours being the lowest jet figure recorded in any year. Nevertheless, there is no obvious downward trend over recent years. The average number of passenger fatalities per fatal accident in 1968 works out at 39. This is slightly higher than the figure of 34.5 for 1967 but considerably below the 1966 figure of 65. The average number of passengers killed per jet fatal accident during the last five years works out at 45 and the average number of survivors as 19. We turn now to the analysis toy three-million-hour periods which was mentioned earlier. The operational total-loss rate and the fatal accident rate are both shown in Fig 10. Both rates show considerable fluctuation, some three-million-hour periods clearly being twice as good (or bad) as adjacent periods. The last three million hours flown is shown to have been a good period, but in view of the fluctuation this can hardly be taken as significant. Three million hours are now being flown in about four months and this suggests that, although a particular year may show a reduction in the total-loss rate compared with previous years, there may well be "bad" periods in the course of the year, during which the short-term total-loss rate is very much above the yearly average. Unfortunately, it is these bad patches, rather than the end of the year facts and figures, which are likely to affect the public image of air transport Fig 8 Fatal-accident rate per lOO.OOOhr 02 0-1 - 60 62 \ V 64 "•" 66 i 68
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