Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
NE-20-05
April 6, 2020
This is information only. Recommendations
aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin (SAIB) alerts
registered owners, operators, and certified repair facilities of all
airplanes equipped with Continental Aerospace Technologies, Inc.
O-470-U, IO-470, IO-520, L/TSIO-520, LIO-520, IO-550, IOF-550,
TSIO-550, and TSIOL-550 series reciprocating aviation gasoline (AvGas)
engines of possible fatigue failure of camshaft gear teeth resulting in
loss of engine power in-flight and forced landings, and of available
service instructions that introduce improved camshaft gear, part number
(P/N) 656818. The service instructions also provide inspection,
removal, and installation procedures for replacing superseded camshaft
gear, P/N’s 631845, 655430, 655516 and 656031, with P/N 656818.
At this time, the airworthiness concern is not an unsafe condition that
would warrant airworthiness directive (AD) action under Title 14 of the
Code of Federal Regulations (14 CFR) part 39.
Background
This SAIB was prompted by reports of fractured camshaft gear teeth,
which resulted in the loss of engine power in flight and forced
landings. Continental performed a metallurgical analysis of an exemplar
camshaft gear, P/N 655516, and the results indicated evidence of
fatigue cracking initiating at the surface of the gear tooth root. The
cause of fatigue crack initiation is not known. The gear met hardness
requirements, and no material anomalies were identified. These findings
are consistent with findings from the metallurgical analysis of other
camshaft gear failures.
Continental introduced camshaft gear, P/N 656818, with an increased
thickness as a product improvement in Continental Service Bulletin
SB05-8, initial release, dated August 9, 2005, and recommended its
installation at the next engine overhaul or whenever camshaft gear
replacement was required. Continental also specified a repair for
Permold crankcases with its installation to eliminate potential
interference with the new, thicker camshaft gear.
Continental subsequently recommended replacement of camshaft gear P/N’s
631845, 655430, 655516 and 656031 with P/N 656818 at engine overhaul in
Continental SB97-6B, dated November 18, 2009. This information has been
incorporated into the Instruction for Continued Airworthiness,
Continental Standard Practice Maintenance Manual M-0.
With the publication of Continental Critical Service Bulletin CSB05-8D,
dated August 22, 2018, Continental specified a 100-hour or annual
inspection, depending on airplane operation or inspection program, or
at the next maintenance event when the camshaft gear is accessible,
whichever occurs first, for camshaft gear P/N’s 631845, 655430, 655516
and 656031 on the affected engine models. The recurring inspections,
for physical damage, fractures or cracks on all visible camshaft gear
surfaces, continue until the aforementioned camshaft gears are replaced
with P/N 656818, no later than the next engine overhaul.
There have been no reported failures of camshaft gear, P/N 656818.
Recommendations
The FAA recommends that repair stations, owners, operators and
maintenance personnel perform the inspections of camshaft gear P/Ns
631845, 655430, 655516 and 656031 until installation of the improved
superseding camshaft gear P/N 656818, as these inspections and
replacement as outlined in Continental CSB05-8D, dated August 22, 2018.
For Further Information, Contact
Boyce (Trey) Jones, Aerospace Engineer, Atlanta ACO, 1701 Columbia
Ave., College Park, GA 30337; phone: (404) 474-5535; fax: (404)
474-5606; email: Boyce.Jones@faa.gov
For Related Service Information Contact
Continental Aerospace Technologies, Inc. Customer Services, 2039 South Broad Street, Mobile, AL 36615; phone: (800) 326-0089