Output Number
Approval Date
Organisation
Federal Aviation Administration
Published Date Time
Recommendation type
Status
Mode
Date released

The Federal Aviation Administration should note the safety
deficiency identified in this document and take appropriate action
as considered necessary.



As a result of investigation into this occurrence, the Bureau
simultaneously issues the following interim recommendations and
safety advisory notice:





IR19990112



The Bureau of Air Safety Investigation recommends that the engine
manufacturer AlliedSignal audit the process employed to manufacture
TPE 331 turbine wheel knife-edged seals to determine those factors
that may lead to excessive variations in slot corner radii.





IR19990113



The Bureau of Air Safety Investigation recommends that the engine
manufacturer AlliedSignal determine the sensitivity of turbine
wheel seals to the initiation of fatigue cracks from slot corners,
as a function of slot corner radii.





IR19990114



The Bureau of Air Safety Investigation recommends that the engine
manufacturer AlliedSignal consider, during engine design and the
formulation of continuing airworthiness instructions, the
possibility that turbine wheel seal fatigue failure may result in
hazardous modes of engine failure.





IR19990115



The Bureau of Air Safety Investigation recommends that the Civil
Aviation Safety Authority Australia conduct an audit of that part
of the aviation safety system that establishes the operational
history of life-limited components, to establish why the
operational history of second-stage turbine wheel, p/n 868272-1,
s/n P03214C, could not be determined with certainty.

Organisation Response
Date Received
Organisation
Federal Aviation Administration (FAA)
Response Text

The office of accident investigation is in receipt of your
recommendations concerning "TPE 331 Turbine Wheel".



Your recommendations have been forwarded to the appropriate office
for response, which is normally 90 days. Your recommendations have
been identified as 99.333 through 99.335, and inquiries should
reference these numbers.



You will be kept informed as to the progress and final resolution
of your submission. If you have any questions, please contact this
office.