ECi Cylinder Head Failures o

Continental IO 520 & 550 Eng

Briefing for Dorenda Baker

June 16, 2013

Chip Queitzsch CSTA

Wayne Maguire ANE
Cylinder Head Failures

• Cylinder head fatigue failure is

a

historical failure mode for GA

reciprocation engines

– Rates have improved significantly

with OEM design refinements

• Cylinder construction: Aluminum

head threaded/shrink fit to steel

cylinder barrel

• Fatigue life of cylinder head

controlled by installation shrink fit

and local feature geometry

• Typical failure site in top threads

• Operating conditions can have

adverse effect on head fatigue life

• OEM and PMA cylinders are

operated similarly

Bar

Cylin

He

Failure

Site
ECi PMA Design Deficiencie

• Concerns regarding rigor in reverse engineering of geome

and validation of design:

– Head shrink fit less than TC’d design

– Stress relevant features not copied precisely

(radii, wall thickness)

• ECi has incrementally increased shrink fit in recent years

• Field service indicates incremental reductions in failure rat

• Current shrink fit still allows assembly less than TC’d design

• AEC/ECi recently contracted for analysis support

– Analysis identifies shrink fit criticality

– Analysis also identifies operation temperature as a potenti

contributing factor

– If PMA cylinders accurately replicated the TC’d design and pilot e

root cause, then TC and PMA cylinders should have similar failure 

• Applicant claims original shrink fit can be established from

disassembled new or used parts

– But applicant does not acknowledge whether they have or 

measured TC’d parts to check TC’d design shrink fit
Cylinder Head Failure Rate

The ECi failure rate

is 32 times higher

than Continental’s

TCM = Conte
Propulsion System Structur

Failure and GA Accidents/Fata

Propulsion 

Failure is th

minor and sand #3 caus
ECi Rebuttals Placed in Perspe

• “Root cause is operator error” (over temperature)

– FALSE: ECi and TC cylinders are operated similarly

failure rate is 32x greater. (OT exacerbates inadequate shr

• ECi has fewer failures relative to Continental (

– MISREPRESENTS FACTS: ECi failure rate is 32x wor

current TC’d design

Old TCH designs

are retired (AD’d),

current design is

comparison basis
Risk Assessment

• Use of typical risk tools limited by incomplete 

data... primary issue is under‐reported event

• High reliance placed on event scatter plot an

rate in each population (only using reported events)

• Resulting AD decision consistent with recip e

risk policy (PS‐ANE‐100‐1999‐00006).

– Same result with and without consideration of Ba

fatal accident triggered by ECi cylinder failure.

(NOTE: Recip policy does not have a CAAM style statistical assessm

• Resulting AD is also consistent with earlier EC

other engine cylinder ADs issued since 2005.

– Examples: 2009‐26‐12, 2009‐19‐07, 2009‐16‐03
Recommendation

• The proposed AD of ECi cylinders produced p

the 2009 shrink fit change is warranted

• Field service shows ECi failure rate is 32x higher than the TC

• At least one foreign fatal accident associated with the ECi P

• FAA GA Safety Study shows Propulsion System structural fa

the #3 cause of fatalities and #2 cause for serious and mino

• Requirements in the Recip policy for issuing an AD are met

• Earlier TC and PMA designs with similar or gr

failure rates have been AD’d

• Main difference for this action is the greater number of eng

affected (larger fleet size and magnitude of ECi presence in 

• ECi argument against AD based on no failures in new produ

this ignores the threat to the in service fleet with pre

‐2009 

(engines subject to the AD)