Cessna 208 Caravan PWC PT6A 114 Series Engines Oil Transfer
Fitting (elbow) Failures
AWB 72-004 Issue : 1
Date : 8 February 2010
Effectivity
All Cessna 208 Caravans powered by Pratt & Whitney Canada
(PWC) PT6A 114 Series engines.
Purpose
Advise operators and maintainers to consider undertaking specific
maintenance actions with regard to Engine Mount Bracket Assy
Attach. P/N 9910333-1 (vibration isolator) and P/N 310365501 oil
transfer fitting or “elbow”.
Background
A preliminary investigation by CASA and the ATSB into the recent
spate of PT6A in-flight engine shut-downs, indicates a possible
link between the incorrect installation of an Engine Mount Bracket
Assy Attach. P/N 9910333-1 (vibration isolator) and fatigue
cracking of the P/N 310365501 oil transfer fitting or
“elbow”.
Fatigue failure of the oil transfer fitting may allow engine oil
to be pumped overboard.
As far as can be determined at this point of the investigation,
the evidence suggests that there is a possibility that the fatigue
failure of this fitting may be caused by unusual vibration caused
by the incorrect installation of the upper vibration isolator, for
example, the aft portion installed inverted or up-side down.
Recommendation
As a precautionary measure, it is recommended that all operators
of the affected engines installed in Cessna 208 aircraft accomplish
the following before further flight:
All instances of incorrectly installed
vibration isolators and/or cracked elbows should be reported to
CASA via the SDR system to assist the on-going investigation.
Inspect all Engine Mount Bracket Assy Attach. P/N 9910333-1
vibration isolators to ensure correct installation and serviceable
in accordance with approved data.
Perform a close inspection on all P/N 310365501 elbows for any
signs of cracking.
Immediately remove from service any elbow with cracking
indications or that has been in service on an engine with an
incorrectly installed engine mount / vibration isolator.
Enquiries
Enquiries with regard to the content of this Airworthiness
Bulletin should be made via the direct link e-mail address: AirworthinessBulletin@casa.gov.au
Or in writing, to:
Airworthiness Engineering Branch
Civil Aviation Safety Authority
GPO Box 2005, Canberra, ACT, 2601
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