Blade off testing

Blade off testing is a specific form of air safety testing required by the Federal Aviation Administration and other safety agencies to certify safety performance of jet engines. The tests require engine manufacturers to carry out at least two tests of the engine, to make sure that the engine can survive a compressor or fan blade breaking off within the engine and a turbine blade breaking off within the engine, without fragments being thrown through the outside enclosure of the engine. The tests are specified by Title 14, Part 33 Subpart F, 33.94 of the US Code of Federal Regulations (CFR), Blade containment and rotor unbalance tests.[1]

The testing usually requires a specially prepared compressor or turbine blade with an embedded small explosive charge, to separate it on command during the test.

The containment requirement and testing requirement were imposed after review of the history of uncontained engine failures which caused serious damage to aircraft. The rule did not apply to engines which were already in service, and an uncontained engine failure of the Number 2 (tail) General Electric CF6 engine of United Airlines Flight 232 on July 19, 1989, caused the hydraulic failure and crash landing of that aircraft.

The tests and standard do not require that the engines continue to operate after the blade failures, only that no fragments penetrate the engine outer casing and that it does not vibrate badly enough during its shutdown that it will tear loose from the aircraft, barring other failures.

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References

  1. ↑ Blade containment and rotor unbalance tests. Archived June 12, 2011, at the Wayback Machine., 14 CFR 33.94, 1984
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