Military Aircraft

C-17 Wing Flap Requires Additional Testing Gao ID: NSIAD-92-160 July 8, 1992

The C-17 military transport aircraft being developed for the Air Force by McDonnell Douglas is designed to land in small or difficult airfields by approaching at much lower speeds and with steeper descents than conventional aircraft. Flap performance is vital to the C-17's unique capability, but testing an early flap design showed that the flap had a life expectancy of about 400 flight hours, far short of the contract performance requirement of 30,000 flight hours. The contractor has strengthened the flap design but has not retested it. GAO believes that the Air Force should establish test plans for the flap before the aircraft goes into production.

GAO found that: (1) the Air Force's review of the contractor's test results raised serious concerns about whether the current flap design could meet the contract performance requirement of 30,000 flight hours; (2) the Air Force and the contractor have begun to acquire flight test data from the developmental aircraft, which will result in assessments of aircraft performance, but will not yield flap life-expectancy estimates; (3) to obtain life-expectancy estimates, the acquired data would have to be used in an environment test that would account for the effects of sound and heat on the flap; and (4) the contractor believes that additional testing is unnecessary and plans to rely on analysis and extrapolation from the actual data.

Recommendations

Our recommendations from this work are listed below with a Contact for more information. Status will change from "In process" to "Open," "Closed - implemented," or "Closed - not implemented" based on our follow up work.

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