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corrective action for certain new ECi
cylinders used on TCM engines.”
NTSB and FAA representatives
formed a task force in 2005 to study
fatigue failures of cylinder heads, which
at that point included domestic and
foreign failures. In 2006, the task force
visited several facilities, including ECi,
and observed the entire manufacturing
process, from casting of the cylinder
heads to cylinder assembly. The NTSB
continued examining failed cylinders
and updating the FAA’s aircraft certification
office responsible for oversight
of ECi. Following a meeting of NTSB,
FAA, and ECi representatives in October
2006 to discuss the cylinder head fa tigue
failure issue, ECi designed and manufac
tured a fatigue test fixture that simu
lates the cylinder head temperature
and pres sure cycles experienced by a
cylin der on an operating engine. After
run ning numerous tests, ECi changed
the manu acturing process for its
cylinder assem blies in October 2009
to pro vide an increased interference
fit at the shrink band and between the
cylinder head and the cylinder barrel
threads but remaining within the limits
of the approved design.
During a meeting in January 2011
between ECi, the FAA, and the NTSB,
ECi produced data on the cylinder
assem bly failures and recommended
that the FAA issue an AD to mandate
inspection and replacement of any
discrepant cylinders; however, the FAA
has not taken the recommended action
for those cylinders not currently covered
by an AD. Since the design improvement
in October 2009, there were no reported
cylinder head fatigue fail ures on ECi
cylinder assemblies installed on model
520 and 550 engines before the January
2011 meeting. Although ECi’s changes
to the manu facturing process may increase
the fatigue strength of new production
cylinder heads, a large population
of potentially discrepant cylinder
assem blies remains in service without
any required corrective action.
Volume 13 • Number 1 AMERICAN BONANZA SOCIETY 27