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in service is Figure 4, "Accidents Caused by In-Flight Fires." The importance of this plot may be shown by the fact that accidents from this cause are twice as apt to be fatal as those from all causes.

In this figure there are three periods of note. First is the tremendous improvement in the period from 1938 to 44. The abrupt drop to the almost perfect record of 1940 through 44 can be attributed to two factors, the mandatory introduction of feathering propellers and the extremely reliable Wright and Pratt and Whitney engines in common use during that period. Of these we believe the ability to stop rotation of a failed or failing engine was undoubtedly the dominant factor.

The second interesting period is the marked jump in the curve for 1945 through 48. This was the time when the modern four engine transports, with extremely high power engines, were first put into service. The record speaks for itself in showing that the in-flight fire situation was not what it should have been when these planes were in their early development stages.

The final period is the abrupt drop off from the peak year, 1948, showing that the previously hazardous conditions have been brought under reasonable control, through the close cooperation of the manufacturers, airlines, and CAA.

There have been, however, some instances of slow or ineffective corrective efforts which have upset the pilots and often tend to becloud the really excellent general efforts. Perhaps the most spectacular one is the high incidence of uncontrollable engine fires in a widely used modern transport. In 1945, in the military prototype, the first such incident occurred, resulting in a fortunate successful forced landing. In 1946 a similar incident occurred in commercial operation. The cause of these initial fires was determined and corrected, but apparently the extinguishing problem was not solved for we find in 1947 and again in 1950 fatal accidents caused by engine fires which the flight crews were unable to control. Again, last year, there was another such incident, but happily, as in the initial ones, a successful forced landing was made. In this unfortunate and lengthy history there have been several different causes for the initial fires which have been subsequently corrected in each case, but the underlying basic accident cause, uncontrollability, was dealt with inadequately with tragic results.

Another problem which undermined the confidence of pilots who know the details dealt with propellers. In this instance, after several vivid, but fortunately non-fatal, demonstrations of what happens when a blade snaps,a program was set up to replace the defective type with improved ones over a considerable