Engineer Describes Fatigue Tests Made On Comet IV

Press, Volume XCVIII, Issue 28824, 19 February 1959, Page 14

Engineer Describes Fatigue Tests Made On Comet IV

The Comet IV airliner was the most tested aircraft in the world, and the only one in which an extensive series of destructive tests had been carried out, said Mr R. Shepherd, who has been appointed as a lecturer in civil engineering at the University of Canterbury, in Christchurch yesterday. Mr Shepherd worked for two years and a half with the de Havilland Aircraft Company, on the metal fatigue tests on the airliner.

Born in York, England, Mr Shepherd graduated B.Sc. in engineering, with honours, at the University of Leeds. From there he went to the de Havilland works, at a time when extensive investigations were being carried out to determine the cause of the break-down of Comet airframes, which had caused several disastrous crashes. For some time, Mr Shepberd worked on the structural pressure tank, in which the fuselage and . wings of a Comet were

“taken up” to a simulated 40,000 ft and back again, and tbs stresses encountered In high-level flight were applied. Massive pumps in a huge test tank simulated the pressure variaticoi by the use of water. The normal cabin pressure In the Comet is Bilb per square inch, and the pressure differential was adjusted accordingly, to allow for the effects of a rapid elimb and descent, said Mr Shepherd. Iks cycle, the equivalent of a threehour flight, was repeated every 4 minutes, 24 hours a day, for about four months. "In the process we broke two aircraft, costing about £300,000 each,’’ said Mr Shepherd. "AS I result of the tests, however, the Comet rv is one of the safest

planes flying today.” The fuselage "skin” of the Comet was about the thickness of cardboard, said Mr Shepherd. And an Increase of a mere tenth of an inch had the effect of doubling the possible fatigue life. “The structural testing wea mainly of an ad hoc nature,” he said. “We made the modifications and then saw what effort, they would have by using the Mr Shepherd caipe to New S&i*-'’ land about a year ago, to work for the- district office of structural design of the Ministry of Works in. Auckland. While in Christchurch, he will carry out ' search on the vibrations fiC working structures, with particular application to seismic work and the designing of buildings and structures to withstand earthquakes.