The Australian Transport Safety Bureau (ATSB) is recommending that Transport Canada reviews the continued airworthiness of Pratt & Whitney Canada PT6A engines. The ATSB has acted because of the type's susceptibility to failure of the number one bearing due to electrical discharge damage from a starter-generator malfunction.
The recommendation is one of a number issued by the ATSB following release of its final report into a forced landing on to a lake in Tasmania last year of a Cessna 208 floatplane after engine failure due to a previous generator failure. During its investigation the ATSB found 43 similar events reported worldwide since 1992.
The ATSB has issued 10 recommendations to Cessna, Australia's Civil Aviation Safety Authority, P&WC, Transport Canada and the US Federal Aviation Administration, with the bureau expressing concern that safety issues need to be addressed to eliminate the possibility of electrical discharge damage leading to engine failure.
The formal release of recommendations follows the ATSB rejecting the views of P&WC, Cessna and Transport Canada in a number of areas following release of an earlier draft report into the incident.
The Australian single-engined Cessna 208 was on a commercial scenic flight in south-western Tasmania with a pilot and 10 passengers on board when an engine chip-detector warning light came on. Within minutes the engine failed and the pilot successfully made a forced landing. The ATSB found that a previous generator failure led to electrical discharge damage, which is a known problem with the PT6, resulting in its failure in-flight.
Among its recommendations, the ATSB says that PW&C consider requiring the removal of any PT6A series engine from service where there is evidence of electrical discharge damage.
Source: Flight International
