Airmotive Engineering

AEC631397 Cylinder Assemblies

Development of an Operational 

Safety Program

FAA Review 6-1-2011
Discussion Topics

• Review and Identification of COS Groups

• Identify Essential Elements of COS Program

– Proposed MSB

• Weibull Statistical Analysis 

– Assess Usage Rates, Field Operation Influence, 

Maintenance Influence

• Summary & Observations of Weibull Analysis

• Recommendations

– Define MSB

– General Field Action

6/1/2011 D. Kenton 2
Review

• 33 Reported Separations of Cylinders

– August 2002 through July 2010

• Cylinder Head/Barrel Separations from Fatigue

– Head fillet radius – improper heat treatment

– Head fillet radius – inherent design deficiency

– First loaded thread – inherent & induced design 

deficiency

– Not confined to AE units (Sky Ranch Manual)

• Cylinder Wall Cracking 

– not causing separations

6/1/2011 D. Kenton 3
Review (ctd)

• Adjustments

– MSB4-1 to recall improperly heat treated units

– MSB6-2 to address wall cracks

– Revised head casting to (AEC65385 Rev. E) to 

increase wall thickness

– Increased head fillet radius to eliminate radius 

fatigue cracking

– Introduced intake valve seat with Allison back to 

increase intake side head wall thickness

– Increased interference fit to relieve thread loading

6/1/2011 D. Kenton 4
Review (ctd)

• Key Design Parameters

– Interference

• By measurement of TCM units

• Measured 0.01 to 0.012-inch at shrink band

• Minimal at threads

– Interface Temperature Design Point

• Test data from similar design

• Head temperature near barrel 405F at CHT = 460F

• Barrel temperature adjacent to head 360F at CHT = 

460F

• Assumed design point at 375F

6/1/2011 D. Kenton 5
Review (ctd)

• Previous Key Findings and Recommendations

– Significant influence of field servicing and operation

– Found Through Additional Review of Data

• AE Cylinders replicated OEM design

• AE replication and embodiment of design incorporated 

inherent deficiencies of the OEM 

6/1/2011 D. Kenton 6
Review (ctd)

• Previous Key Findings and Recommendations

– Group MSB6-2, SN1 – 33689-24 

• Date Range: 9/1/02 – 11/29/05

• A small number of units had elevated risk of radius 

fatigue

• Modify MSB6-1

– Include fins 4-7 & 9-10 for visual crack inspection

– Remove all 4-1 and 6-2 units at next teardown

– Scrap all removed cylinders

6/1/2011 D. Kenton 7
Review (ctd)

• Previous Key Findings and Recommendations

– Group Post MSB6-2, SN 33690-01 – 64016-27 

• Date Range: 12/1/05 – 10/12/09

• Small % of units at elevated risk thread fatigue

• Issue MSB similar to MSB6-2

– Begin repetitive inspections at within next 50 hours

– Include fins 4-7 & 17 for visual crack inspection

– Remove all Post 6-2 units at next teardown

– Scrap all removed cylinders

6/1/2011 D. Kenton 8
Cylinder Groups for COS Discussion

GROUP QUANTITY RETURNS SEPARATIONS NET

MSB6-2 16,187 756 25 15,406

PMSB6-2 20,937 40 8 20,890

TOTALS 43,767 796 33 42,938

Note: 4,501 PMSB6-2 produced with Allison Back Intake Valve Seats

6/1/2011 D. Kenton 9

MSB6-2: 

•AEC65385 rev. D - Cylinder head wall at fin 17

•0.030-inch fillet radius

PMSB6-2

•AEC65385 rev. E – Increase cylinder head wall at fin 17

•0.045-inch fillet radius
Essential Elements of a New MSB

• Identify groups by serial number range

• Inspect for problem cylinders

– Remove improperly operated or damaged units

• Mitigate field operation and servicing factors

– CHT systems

– EGT systems

– Cooling Baffles

– New Cylinder Installation and Break-in

6/1/2011 D. Kenton 10
Weibull Analysis

• Develop Bracketed range for risk assessment

– From Report 1102-13

• Actual to Standard Mean = 2.9

• Coefficient of Variation = 1.21

– For Comparative Analysis Use a Ratio of 2

• Standard use = 100 hr/yr

• Accelerated use = 200 hr/yr

– Basis

• All reported failures considered separations

• TIS is reported time in service (hours)

• Assume radius failure prone units removed

6/1/2011 D. Kenton 11
Actual/Standard Hours Correlation

6/1/2011 D. Kenton 12

0

200

400

600

800

1,000

1,200

1,400

0 200 400 600 800 1,000 1,200 1,400

Time in Service Hours

Standard Hours
Weibull Analysis (ctd)

• Consideration Factors Group MSB6-2

– Last failure date 7/14/10

– All failed units produced and shipped in 2004

– 18 of 21 failures occurred at less than 500 hours

– Maximum fleet time = 763 to 1546 hrs

– Minimum fleet time = 508 to 1016 hrs

– Characteristic life of radius failures about 1200 hr

– Explore field service and operation influence

6/1/2011 D. Kenton 13
Weibull Analysis (ctd)

• Consideration Factors Group Post MSB 6-2

– All observed failures were in first loaded thread

– Three failures exceeded fleet use rate by at least 

60% to as much as 220%

– Short time suspensions affect Weibull curve shape

– 4500 units produced with heads having increased 

intake side will thickness (use of intake seats with 

Allison style back)

– Explore field service and operation influence

6/1/2011 D. Kenton 14
Weibull Analysis (ctd)

Group MSB 6-2 Evaluation

MSB6-2 MSB6-2 thru 2004

100/yr 200/yr 100/yr 200/yr

Consol. Consol. Consol. Consol.

Var. A Var. A Var. A Var. A

Var. B Var. B Var. B Var. B

Group Post MSB6-2 Evaluation

P MSB6-2 P MSB6-2 + 2005

100/yr 200/yr 100/yr 200/yr

Consol. Consol. Consol. Consol.

Var. A Var. A Var. A Var. A

Var. B Var. B Var. B Var. B

6/1/2011 D. Kenton 15
6/1/2011 D. Kenton 16

Weibull Function





= Fraction failing up to time, t (CDF)

= Failure time

= Slope or shape parameter

=Characteristic life or scale parameter

F(t)



















 

t

F(t) 1 e

t
6/1/2011 D. Kenton 17

Weibull Analysis (ctd)
Weibull Analysis (ctd)

6/1/2011 D. Kenton 18
Weibull Analysis (ctd)

6/1/2011 D. Kenton 19
Weibull Analysis (ctd)

6/1/2011 D. Kenton 20
Weibull Analysis (ctd)

6/1/2011 D. Kenton 21
Weibull Analysis (ctd)

6/1/2011 D. Kenton 22
Weibull Analysis (ctd)

6/1/2011 D. Kenton 23
Weibull Analysis (ctd)

6/1/2011 D. Kenton 24
Weibull – Group 6-2 Summary

6/1/2011 D. Kenton 25

GROUP VAR. ETA BETA B = .1% B = .5%

6-2 (100/YR) A 12,537 1.998 396 886

B 4,839 3.803 787 1202

6-2 (200/YR) A 12,537 1.998 396 886

B 11,746 2.791 989 1762

6-2 THR. 2004 (100/YR) A 10,097 1.999 319 714

B 5,840 3.367 751 1211

6-2 THR. 2004 (200/YR) A 10,111 1.999 319 714

B 10,070 2.791 848 1510
Weibull – Group P6-2 Summary

6/1/2011 D. Kenton 26

GROUP VAR. ETA BETA B = .1% B = .5%

P6-2 (100/YR) A 147,796 1.361 924 3,021

B 1,087 8.903 500 600

P6-2 (200/YR) A 1,265,527 1.055 1,818 8,372

B 1,123 28.81 884 935

P6-2 + 2005 (100/YR) A 342,790 1.244 1,330 4,858

B 1,108 6.143 360 468

6-2 + 2005 (200/YR) A 1,613,961 1.049 2,228 10,354

B 2,380 9.332 1,121 1,332
Weibull Analysis Observations

6/1/2011 D. Kenton 27

• Splitting data points improves fit

• Higher baseline use identifies influence of field 

operation and maintenance

• Shifting MSB6-2 year 2005 to Post MSB6-2 isolates all 

MSB6-2 units that were prone to premature 

separation

• Proposed MSB should be structured to address high 

and low time MSB6-2 units produced through 2004

• Variant A probably represents improper cylinder 

conditioning
Weibull Analysis Observations

6/1/2011 D. Kenton 28

• Variant B probably represents over temperature 

operation

• Address Variant A by removing glazed cylinders

– Scrap MSB6-2 through 2004

– Remove and Hone PMSB6-2 with less than 75 hours

• Address Variant B by calibration and maintenance

– Calibrate CHT system and each 24 months thereafter

– Calibrate EGT system and each 24 months thereafter

– Check and reset all engine cooling devices
Recommendations for MSB

• Cylinder Serial No.

– 1 through 25526-22 = Group A

– 25527-01 through 64016-27 = Group B

• Group A Actions

– Cylinders with less than 750 hours TIS 

• Initial inspection as defined in this MSB within next 50 hours

• Recurrent inspection each 50 hours as defined in this MSB

• Remove from service at 750 hours

– Cylinders with more than 750 hours TIS 

• Initial inspection as defined in this MSB within next 50 hours

• Recurrent inspection each 50 hours as defined in this MSB

• remove from service within next 250 hours or at next engine teardown 

whichever comes first

6/1/2011 D. Kenton 29
Recommendations for MSB (ctd)

• Group B Actions

– Cylinders with less than 1000 hours TIS 

• Initial inspection as defined in this MSB within next 50 hours

• Recurrent inspection each 50 hours as defined in this MSB

• Remove from service at 100 hours if CHT system is not calibrated as 

defined in this MSB

• With CHT calibration continue in service to TBO with repetitive 50 hour 

inspections

– Cylinders with more than 1000 hours TIS, 

• Initial inspection as defined in this MSB within next 50 hours

• Recurrent inspection each 50 hours as defined in this MSB

• Remove from service within next 50 hours if CHT system is not calibrated 

as defined in this MSB

• With CHT calibration continue in service to TBO with repetitive 50 hour 

inspections

6/1/2011 D. Kenton 30
Recommendations for MSB (ctd)

• Visual and operation inspection

– Confirm serial number and MSB applicability

– Cracks at head fins 17, 5-7, and 9-10 counting from bottom

– Remove cracked cylinders

– Check for excessive oil consumption

– Check if cylinder(s) has(have) not been installed and 

conditioned as part of a test cell break-in procedure

– Check for evidence abnormally high operating 

temperatures

– Check for proper configuration of cooling baffles

– Check for proper cowl flap operation if installed

6/1/2011 D. Kenton 31
Recommendations for MSB (ctd)

• Cylinder compression check 

– Check per ECi TN 10-4 

– Soap bubble leak check as needed (Ref, TCM SB 96-12)

– Remove cracked cylinders

• Crankcase Pressure Test

– If excessive oil consumption (1 qt/3 hour)

– If any of the installed cylinders have not been conditioned 

in a test cell

– Conduct test as defined by TCM Service Bulletin M89-9

6/1/2011 D. Kenton 32
Recommendations for MSB (ctd)

• Crankcase Pressure Test (ctd)

– Remove cylinders if crankcase pressure exceeds limit

– Group A cylinders

• remove from service

– Group B cylinders with less than 75 hours in service

• Remove, hone, install, and properly break-in

– Group B cylinders with more than 75 hours in service

• Remove from service

6/1/2011 D. Kenton 33
Recommendations for MSB (ctd)

• CHT System

– Calibrate instrument and thermal probe

– At initial inspection and each 24 months or 200 hours 

thereafter

– Standard ASTM calibration procedures

• EGT System

– Calibrate instrument and thermal probe

– At initial inspection and each 24 months or 200 hours 

thereafter

– Standard ASTM calibration procedures

6/1/2011 D. Kenton 34
Recommendations for MSB (ctd)

• Engine Cooling Devices

– Inspect all cooling baffles & restore to certificated 

condition as needed

– Inspect cowl flap system and reset to certificated 

condition as needed

6/1/2011 D. Kenton 35
General Recommendations

• SAIB from Engine Test 

– Measure Interface Temp

– Compare proper and improperly conditioned cylinders

• Fleet CHT System

– Calibrate instrument and thermal probe

– At initial inspection and each 24 months or 200 hours thereafter

– Standard ASTM calibration procedures

• Fleet EGT System

– Calibrate instrument and thermal probe

– At initial inspection and each 24 months or 200 hours thereafter

– Standard ASTM calibration procedures

• Fleet Break-in Procedures

– Publish standard

6/1/2011 D. Kenton 36
Supplemental Information
AEC631397 Cylinder Separations

S/N Type Class Engine Shipped Remvd TIS 

(hrs)

Failure 

Location

MSB

4464-24 TIST 71.2A IO-520F 1/20/03 3/31/03 87 radius 4-1

4360-32 TIST 71.2B TSIO-520 1/15/03 12/2/08 218.1 radius 4-1

5482-19 TIST 71.2A 2/14/03 9/3/03 283 4-1

7141-16 TIST 71.2A 4/14/03 11/15/03 269 4-1

7819-23 TISN 71.2B TSIO-520NB 5/23/03 4/23/04 204 6-2

8013-28 TISN 71.2B 5/19/03 8/12/09 960 radius 6-2

12612-5 TISN 71.2B TSIO-520NB 10/10/03 4/28/04 200 6-2

13515-11 TISN 71.2B TSIO520-NB 1/5/04 6/15/10 360 thread 6-2

13515-26 TISN 76.0 IO-550D 2/5/04 8/12/08 338 thread 6-2

13670-3 TISN 71.2C 1/22/04 4/18/06 1301 6-2

6/1/2011 D. Kenton 38
AEC631397 Cylinder Separations (Ctd)

6/1/2011 D. Kenton 39

S/N Type Class Engine Shipped Remvd TIS 

(hrs)

Failure 

Location

MSB

16757-6 TISN 71.2B TSIO-520NB 4/1/04 3/18/05 475 6-2

18700-1 TISN 71.2A IO-55F 6/17/04 5/1/09 663 thread 6-2

19441-28 TISN 71.2A IO-520D 7/23/04 6/5/07 290 6-2

20940-22 TISN 76.0 IO-550F 8/19/04 12/12/05 89 6-2

21327-19 TISN 71.2B TSIO-520 9/10/04 2/7/05 721 6-2

21432-10 TISN 71.2C IO-550C 8/31/04 10/14/08 355 radius 6-2

21994-21 TISN 71.2B TSIO-520NB 9/16/04 5/11/06 330 6-2

21590-14 TISN 71.2C IO-550B 9/10/04 4/27/09 150 radius 6-2

22241-24 TISN 71.2B TSIO-520NB 10/11/04 7/14/10 264 6-2
AEC631397 Cylinder Separations (Ctd)

6/1/2011 D. Kenton 40

S/N Type Class Engine Shipped Remvd TIS 

(hrs)

Failure 

Location

MSB

22389-9 TISN 71.2B IO-550B 10/5/04 5/3/06 170.2 6-2

22537-24 TISN 71.2B IO-550B 10/5/04 5/3/06 171.7 6-2

22838-19 TISN 71.2B TSIO-520WB 10/20/04 3/11/09 390 radius 6-2

23217-13 TISN 71.2B TSIO-520NB 10/19/04 12/30/08 257 radius 6-2

23343-15 TISN 71.2B 10/26/04 8/1/05 505 6-2

23258-14 TISN 71.2B TSIO-520 11/1/04 5/18/08 423.9 radius 6-2

33947-29 TISN 71.2C IO-550B 11/22/05 11/20/08 210 thread p6-2

34684-13 TISN 71.2C IO-550A 11/6/05 10/1/10 1061 p6-2

35955-22 TISN 71.2B TSIO-520NB 1/6/06 5/20/09 1163 thread p6-2
AEC631397 Cylinder Separations (Ctd)

6/1/2011 D. Kenton 41

S/N Type Class Engine Shipped Remvd TIS 

(hrs)

Failure 

Location

MSB

45312-15 TISN 71. 2 TSIO-520WB 3/2/07 9/12/09 1095 thread p6-2

50785-26 TISN 71.3B TSIO-520WB 11/20/07 4/3/09 196 thread p6-2

51847-12 TISN 71.2B TSIO-520 1/23/08 7/30/10 71.2 thread p6-2

51973-08 TISN 71.2B TSIO-520 1/28/08 8/4/09 835 P6-2

52884-22 TISN 76.0 IO-550F 6/4/08 11/13/08 415.8 thread p6-2

Total 33

MSB4-1 4

MSB6-2 21

Post MSB6-2 8
AEC631397 Not Applicable or 

Untraceable Cylinder Separations

6/1/2011 D. Kenton 42

S/N Type Class Engine Ship Remvd TIS Failure 

Loc

Notes

8009-00 FRST 71.2C IO-550B 12/2/03 1/11/05 409 stripped Freedom

17029-28 CCCN 71.2B TSIO-520-NB 4/19/04 10/28/09 267 stripped Freedom

31265-20 TISN 71.2B IO-520C 7/27/05 6/15/09 417 stripped Freedom

32803-1 TISN 71.2B TSIO-520M 9/12/09 1095 Freedom?

47932-06 TISN 71.2B TSIO-520VB 7/27/07 10/15/10 1254 NA Repaired

9138-00 TISN 71.2A IO-520 4/6/05 1787 No SN Match

UNK-1 TISN 71.2B TSIO-520NB 2/23/10 421

UNK-2 TISN 71.2B TSIO-520N 3/12/08 105

UNK-3 O-470R 2/18/10 151 Not Appl.

UNK--5 TISN 71.2A IO-520F 6/21/05 489
AEC631397 Cylinder Components

Group AEC65385

Head

AEC631399 

Head

Threads

AEC65414 

Head 

Machining

AEC634501 

Barrel

MSB4-1 C G IR, A N

MSB6-2 D H A N, P, R, T

PMSB6-2 E, F K, L C, D U, V

PMSB6-2-INT-A F, J N E V

6/1/2011 D. Kenton 43
Potential Actual/Standard Use Ratio

6/1/2011 D. Kenton 44

S/N Group Shipped Removed TIS (Hrs) STD ()Hrs TIS/STD 

4464-24 4-1 1/20/2003 3/31/2003 87 19.2 4.54

4360-32 4-1 1/15/2003 12/2/2008 218.1 588.5 0.37

5482-19 4-1 2/14/2003 9/3/2003 283 55.1 5.14

7141-16 4-1 4/14/2003 11/15/2003 269 58.9 4.57

7819-23 6-2 5/23/2003 4/23/2004 204 92.1 2.22

8013-28 6-2 5/19/2003 8/12/2009 960 623.8 1.54

12612-5 6-2 10/10/2003 4/28/2004 200 55.1 3.63

13515-11 6-2 1/5/2004 6/15/2010 360 644.7 0.56

13515-26 6-2 2/5/2004 8/12/2008 338 452.1 0.75

13670-3 6-2 1/22/2004 4/18/2006 1301 223.8 5.81

16757-6 6-2 4/1/2004 3/18/2005 475 96.2 4.94

18700-1 6-2 6/17/2004 5/1/2009 663 487.4 1.36

19441-28 6-2 7/23/2004 6/5/2007 290 286.8 1.01

20940-22 6-2 8/19/2004 12/12/2005 89 131.5 0.68

21327-19 6-2 9/10/2004 2/7/2005 721 41.1 17.54

21994-21 6-2 9/16/2004 5/11/2006 330 164.9 2.00
Potential Actual/Standard Use Ratio

6/1/2011 D. Kenton 45

21432-10 6-2 8/31/2004 10/14/2008 355 412.3 0.86

21590-14 6-2 9/10/2004 4/27/2009 150 463.0 0.32

22241-24 6-2 10/11/2004 7/14/2010 264 575.9 0.46

22389-9 6-2 10/5/2004 5/3/2006 171.7 157.5 1.09

22537-24 6-2 10/5/2004 5/3/2006 170.2 157.5 1.08

22838-19 6-2 10/20/2004 3/11/2009 390 439.2 0.89

23217-13 6-2 10/19/2004 12/30/2008 257 420.0 0.61

23343-15 6-2 10/26/2004 8/1/2005 505 76.4 6.61

23258-14 6-2 11/1/2004 5/18/2008 423.9 354.5 1.20

33947-29 p6-2 11/22/2005 11/20/2008 210 299.7 0.70

34684-13 p6-2 11/6/2005 10/1/2010 1061 490.4 2.16

35955-22 p6-2 1/6/2006 5/20/2009 1163 337.0 3.45

50785-26 p6-2 11/20/2007 4/3/2009 196 137.0 1.43

51847-12 p6-2 1/23/2008 7/30/2010 71.2 251.8 0.28

51973-08 P6-2 1/28/2008 8/4/2009 835 151.8 5.50

52884-22 p6-2 6/4/2008 11/13/2008 415.8 44.4 9.37

Mean 274.7 2.90

Standard Deviation 196.9 3.51

Coefficient of Variation 0.72 1.21