Chalk's Ocean Airways Flight 101 - Age of Fleet

Age of Fleet

The accident aircraft had been built in 1947 and the manufacturer, Grumman, had produced only 59 examples of this type. When Grumman ceased production of the aircraft in 1951 this eventually left operators with no source of new spare parts, and the airline operator of the accident aircraft, Chalk's Ocean Airways, had had to resort to acquiring several un-airworthy Mallards to cannibalise for spares. In addition, the sort of aircraft used for Chalk's operations, a passenger-carrying flying boat, is of a type no longer manufactured by aircraft companies, so the option of replacing the ageing Mallard fleet with newer designs was not available. At the time of the accident, the accident aircraft was 58 years old, had accumulated 31,226 total flight hours, and had completed 39,743 take-off/landing cycles.

When certificated in 1944 the Mallard design was required to satisfy a static strength analysis, but no fatigue requirement was yet in force as no satisfactory fatigue analysis method had been developed at that time. The Mallard therefore had not been designed with any 'safe life' figure, unlike most civil transport aircraft today which have designed fatigue lives of around 65,000-70,000hrs, or twenty years. In addition, no authorised repair manual for the aircraft type had been issued by the manufacturer, responsibility for authorising repair techniques having been acquired by an outside company after Grumman discontinued support for the type.

The accident aircraft had been acquired by Chalk's in 1980 and had been upgraded to a G-73T Turbo Mallard in July 1981 when its original Pratt & Whitney Wasp H piston engines had been replaced with Pratt & Whitney Canada PT6 turboprops.