Report 1102

- 13



# Airmotive Engineering Corp

.

2100 Mannix San Antonio, TX 78217
- 5994 Tel (210) 820
- 2450
Fax (210) 820
- 2451 

# REPORT 1102

- 13

Prepared By: D. Kenton, D onald J. Ken to n, Sc. D., LLC

4/30/2011 

# Analysis of AEC631397 Cylinder Assembly

Head

- Barrel Separations 

# Technical ReportReport 1102

- 13

Page 1 

## CONTENTS

ABSTRACT

................................ ................................ ................................ .................. 2

BACKGROUND

................................ ................................ ................................ ........... 3

TECHNICAL APPROACH

................................ ................................ ............................... 3 Design and Service Bulletin Data

................................ ................................ ...................... 3 Production and Warranty Data

................................ ................................ ........................ 4
Visu al Examination

................................ ................................ ................................ ........... 4 Summary Listing of Separated Cylinders

................................ ................................ .......... 4
Statistical Assessment

................................ ................................ ................................ ...... 4 Analysis o f Head

- Barrel Interface

................................ ................................ ..................... 6

RESULTS AND DISCUSSI ON

................................ ................................ ......................... 7 Design and Service Bulletin Data

................................ ................................ ...................... 7 Production and Warranty Data

................................ ................................ ...................... 11
Visual Examination

................................ ................................ ................................ ......... 13 Summary Listing of Separated Cylinders

................................ ................................ ........ 15
Statistical Assessment

................................ ................................ ................................ .... 22 Cylinder Population Group MSB4

- 1

................................ ................................ ............. 22 Population Group SB6

- 2

................................ ................................ ............................... 28 Population Group Post SB6

- 2

................................ ................................ ....................... 34 Repaired Cylinder Assemblies

................................ ................................ ...................... 38 Analysis of Head

- Barrel Interface

................................ ................................ ................... 39 Population Group Identification and Material Properties

................................ ........... 39 Coefficient of Sliding Frict ion

................................ ................................ ....................... 41 Interference Fit Estimates at Operating Temperature

................................ ................ 42
Removal Force Estimates

................................ ................................ ............................. 48

FINDINGS AND RECOMME NDATIONS

................................ ................................ ........ 62
Find ings

................................ ................................ ................................ ........................... 62
Recommendations

................................ ................................ ................................ .......... 64

ATTACHMENT 1. FAA M DR AS OF 1/13/04, AE C631397 SEPARATIONS

...................... 66

ATTACHMENT 2. TENSI LE STRENGTH

- TEMPER ATURE GRAPH FOR A242 .0

................ 67

ATTACHMENT 3. THERM AL EXPANSION COEFFIC IENT FOR SAE4140 STE EL

................ 68

ATTACHMENT 4. COMPU TATION OF THE EFFECT IVE FRICTION COEFFIC IENT

............. 69
Push

- Off Test Data Provided by Airmotive Engineering

................................ .............. 69
Calculations for Friction Coefficient

................................ ................................ ............. 69Report 1102

- 13

Page 2 ATTACHMENT 5. THERM AL EXPANSION COMPUTA TIONS

................................ ......... 72

ATTACHMENT 6. REMOV AL FORCE GRAPHICAL S UMMARY NOMINAL, MAXI MUM, AND MINIMUM FIT CONDITONS

................................ ................................ ................................ ......... 76

REFERENCES

................................ ................................ ................................ .............. 88


## ABSTRACT

A irmotive Engineering produced 43,767 replacement cylinder assemblies for TCM 520/550 series engines from 8/29/02 through 12/31/10. This analysis identified four separate populations, SB4

- 1, SB6

- 2, Post SB6

- 2, Post SB6

- 2

- INT

- A, defined by mandatory service bulletins and design adjustments. Visual inspection and analysis confirmed three failure modes:

1. Fatigue in the head shrink band to dome fillet radius

2. Fatigue in the first loaded head thread

3. Stripped threads in repaired cylinders
Weibull statistical analy sis for population group MSB4

- 1 projected risk of failures driven by thread fatigue. Head fillet radius fatigue failure dominated risk projection s of group MSB6

- 2

. Weibull stati sti cal analysis for group Post SB 6

- 2 revealed a cumulative distribution funct ion for thread fatigues failures with a shape characteristic similar to that of distributions observed for populations prone to fatigue failures in the head fillet radius. Risk projections for group Post SB6

- 2 suggested 5% of the in service population had a significant risk for thread fatigue failure.

Diametrical i nte r ference and press fit removal fo rce computations showed groups SB4

- 1, SB6

- 2,
and Post SB6

- 2 will transfer most , or all , of the combustion load into the thread below the maximum design interface temperature, if assembled at nominal or minimum interference fit. Current production cylinders, Post 6

- 2

- INT

- A, assembled at nominal or greater interference fit
will support more than 50% of combustion load to the thread s at maximum interface design
temperature of 375F

. At minimum interference fit, Post 6

- 2

- INT

- A cylinders will transfer about 85% of the combustion load to the threads at 375F interface temperature

. Increasing the interfe r ence fit of current production cy linders by 0.00 7

- inch should avert all transfer of load to
the threads at minimum interference up to 425F interface temperature.
For improved tracking and management of continued operational safety , we recommend installation of a sequential serial number a ssignment system for cylinder assemblies.
We recommend continuing repetitive inspections described in service bulletin MSB6

- 2 for groups SB4

- 1 and SB6

- 2 , and add ing an examination for cr a cks at fins 5

- 7 and 9

- 10 counting from the bottom of the head

. We recommend creating a service bulletin for group Post MSB6

- 2 calling for repetitive inspections beginning at 250

- hours culminating in permanent removal of these service at the next
scheduled overhaul

. We recommend testing to measure actual cylinder interface temperatures, and consideration of a service bulletin calling for removal and rework of cylinders consuming oil from improper break

- in.Report 1102

- 13

Page 3 

# Report 1102

- 13

A N A L Y S I S O F A E C 6 3 1 3 9 7 C Y L I N D E R A S S E M B L Y H E A D

-

B A R R E L S E P A R A T I O N S



## BACKGROUND

Airmotive E ngineering (AE) AEC631397 cylinder assemblies

, produced under parts manufacturing approval

, intend ed for use in Teledyne Continental (TCM) 520/550 series engines have experienced a
number of head

- barrel separation events attributable to manufacturing induced deficiencies, inherent design deficiencies , and in

- service operation beyond the design operating parameters. AE has issued mandatory service bulletins to address field service issue s , and has incorporated a number of design adjustments to mitigate inherent and induced deficiencies in the assembly. This report investigates head barrel separation events related to cylinders produced beginning in Septe mbe r 2002 through December 2010

. Our investigation will include review of relevant design drawings to identify cylinder assembly configurations, direct examination of available separated cylinder assemblies, assessment of failure frequency and projected risk through statistical methods, and use of material characteristics combined with mechanics to provide guidelines for continued operational safety as well as further design optimization.



## TECHNICAL APPROACH
Broadly speaking our technical approach will comprise a number of elements :

1. Use available data to determine cylinder assembly configuration.

2. Review production and warranty service data to determine the relevant cylinder assembly populations.
3. Conduct visual inspections of separated cylinder assemblies on site at AE facilities.

4. Compile a summary listing of separated cylinder assemblies.

5. Statistically assess the cylinder populations to project failure frequency and risk factors for the relevant populations.
6. Use design information, projected operating conditions, known material properties, and
mechanics to determine guidelines for assessing robustness of the head

- barrel interface cylinders and offer guidelines for potential interface design improvements.



## Design and Service Bulletin Data

This study focuses on those AEC631397 cylinders inte nded for use in TCM 520/550 series, identified as classes 71.2, 71.4, 76.0, and 76.3, and excludes the GTSIO520 series

. With emphasis on the head configuration and head

- barrel interface, this study examined the following drawings:

1. AEC631397, Cylinder As sembly for Classes 71.2, 71.4, 76.0, and 76.3

2. AEC65385, Cylinder HeadReport 1102

- 13

Page 4 3. AEC631399, T hread and Pilot diameters

4. AEC65415, Machining, Cylinder Head

5. AEC634501, Barrel, Cylinder 5.25

- inch Bore
6. AE65041, Choke Configurations

- Opposed Engines

Along with the design data, two service bulletins apply to the subject cylinder assemblies:

1. Mandatory Service Bulletin (MSB) 4

- 1 originally issued 3/4/04.

2. M SB 6

- 2 originally issued 8/25/06.

From this data, we identified the relevant cylinder assembly populations based that would correlate with the applicable MSB and relevant design configuration.



## Production and Warranty Data

AE queried its production database to provide tabular data of all cylinders shipped from 8/29/02 through 12/31/10. Based on the identified cylinder ass embly populations, we created individual databases for each population.



## Visual Examination

The AE quality assurance department retrieved from storage several TCM 520 cylinders that experienc ed a head

- barrel separation. A visual examination of these unit s identified the failure
location and confirm ed the cyclic propagation of the failure.


## Summary Listing of Separated Cylinders

Using FAA Maintenance Difficulty Reports (MDR) and AE data, we compiled a consolidated list of traceable cylinders experiencing a head

- barrel separation. For completeness, we compiled a second listing of those cylinders identified in the MDR's as separated, but not relevant to this study or not traceable. This group includes several repaired cylinders experiencing a head

- barr el separation.

Separately, the FAA provided a listing of cylinders belonging to the population addressed by MSB4

- 1 that had failed. Subsequently, we utilized the FAA provided data and data from repaired cylinders to
assist in estimation of failure rates associated with different failure modes.



## Statistical Assessment

Life limited populations generally conform to a cumulative distribution curve first proposed by Waloddi
Weibull 1 . These distributions are of the form

EQUATION 1

Where:

F(t) = Fraction failing up to time t (Cumulative Distribution Frequency)Report 1102

- 13

Page 5 t = Failure time

β = Shape parameter (slope of a straight line on a log

- log plot)

η = Characteristic life (63.2% of population will fail by characteristic life)

e = base for natural logarithms (2.718281828)

Best practice fitting data to these curves uses median ranked regression analysis rather than mean based rank because of the skew in the data to toward longer lives. Our analysis will rely on the same procedure and use software developed by Abernethy's group (Ref. 1) for this purpose.

Risk projection involves computation of the "Now Risk", which uses the cumulative distribution curve
to confirm the actual numbers of failed articles. Assumi ng actual reported failures generally agrees with the computed Now Risk , we can use the cumulative failure distribution function to project the risk
of failure for units in the field.

Now Risk is given by:

EQUATION 2

Where:

NowRiskRBA = Now Risk with reduced bias adjustment F(t i ) = Cumulative Failure Distribution curve for the population

r = number of failures

s = n um b er of units s till operating (suspensions)

Equation 3 mathematically describes the Failure Forecast:

EQUATION 3

Where:

F(t i ) = probability of failure of unit i in first t i hours F(t i +u) = probability of failure of unit I in the usage period, u

Using best practices, we fit a Weibull type cumulative damage function to each population. When the plots and engineering knowledge suggest multiple failure modes are in play, we will use best practices methodology to identify and group cylinders associated with each failure mode , which permit s creat ion
of separate cumulative damage functions for each failure mode

.

Our st atisti cal analysis will apply the Weibull distribution to the identified failures without field suspensions to assess the curve characteristics. We then assess ed the identifie d populationsReport 1102

- 13

Page 6 incorporating the in service suspensions. This will allow reasonable estimates of failure rate projection and failure forecasting.

Field failures use time in service (TIS), typically hours since installation. However, we do not know TIS
for the population in the field. For in service suspensions the general aviation industry commonly accepts an aircraft use rate of 100 hours per year. Therefore, based on the shipping date for each cylinder identified in the population still in service

, we used a service accumulation rate of 100 hours

per year to estimate TIS

. When warranty data indicates a cylinder returned to AE for consideration

, we considered that cylinder as permanently removed from service. Thus, our standard practice assumed all cyli nders on the production list, less failures and warranty returns

, remain in servic e

. 

## Analysis of Head

- Barrel Interface

Fatigue failure of the first loaded head thread is a known failure mode for these cylinders. Work performed on AEL65102 cylinder assemblies 2 has shown that insufficient interference will result in cyclic load transferred to the threads. Our assessment of the AEC631397 cylinder configuration will begin with estimation of interference fits at head

- barrel interface temperatures betwee n 350F and
425F
, based on known cylinder configurations and thermal expansion coefficients of the head and
barrel material for the following conditions:

1. Nominal

2. Condition 1

- Maximum interference at the shrink band and the threads
3. Condition 2

- Minimum int erference at the shrink band and the threads

4. Condition 3

- Maximum interference in the threads, minimum interference in the shrink band

5. Condition 4

- Minimum interference in the threads, maximum interference in the shrink band

These curves will provide dia metrical data necessary to compute removal force from press fit
assemblies.

Next, we estimate d removal force on press fit cylinder heads and barrels for the following conditions

1. Nominal

2. Condition 1

- Maximum interference at the shrink band and the threads

3. Condition 2

- Minimum interference at the shrink band and the threads

An Excelcals.com program based on press fit formulas found in standard texts on machine design 3 offered a convenient means to estimate press fit removal force. Assuming the threaded are a acts as a smooth wall cylinder at the thread pitch diameter we calculated separ at e removal forces for the shrink band and threaded areas, then added the separate forces to determine the total resistance to removal. These calculations require knowledge o f a number of mechanical and physical properties of the materials of construction including material tensile properties, Young ' s modulus, P oison ' s ratio, and
friction coefficient betwee n head and barrel. Besides shrink band and thread

- pitch diameters

, theReport 1102

- 13

Page 7 calculations require estimation of the following cylinder characteristics at the required operating temperature including:

1. Respective contact lengths of the shrink band and threaded sections

2. Outer radius of the cylinder head
3. Inner radius of the cylinder b arrel

4. Diameter of the piston at the interface temperature and knowledge of measured peak cylinder

pressures

The removal force calculations result in Force

- Temperature curves for each relevant cylinder interface geometry, assembly interference fit, and in terface operating temperature with reference to the
estimated maximum combustion pulse force experienced by the cylinder. A total removal force less than the computed combustion pulse force will indicate cyclic load transfer to the threads.



## RESULTS AND DISCUSSION

Design and Service Bulletin Data

As noted in the Technical Approach

, a number of subordinate drawings provide technical data input necessary to manufacture AEC631397 cylinder assemblies:

1. AEC65385, Cylinder Head

2. AEC65415, Machining, Cylinder Head

3. AEC631399, Thread and Pilot diameters

4. AEC634501, Barrel, Cylinder 5.25

- inch Bore

5. AE65041, Choke Configurations

- Opposed Engines

Table 1 provides a summary listing for relevant drawings and dimensional features supporting AEC631397 cylinder assemblies ap plicable to output classes 71.2, 71.4, 73.0, and 73.6, intend ed as replacement cylinder assemblies for TCM 520/550 series engines.

TABLE 1 . SUMMARY OF SUBORD INATE DRAWING DATA



### Table 1A. AEC65385 Head Casting

Dwg No. Rev Date Chang es/Adjustments Comments

AEC65385 C Bench mark 1. Effective drawing on 8/29/02

2. Combined casting and machining drawing Effective at start of SB4

- 1 Oberdorfer casting

D 3/7/03 Redrawn to separate head machining from

casting Effective through end of SB4

- 1 and through SB6

- 2

E 5/11/05 Added material to exterior wall contour on

exhaust side to minimize cracking Implemented 11/12/05 and covers post SB6

- 2 period through 2/06.

F 2/2/06 1. Minor changes to improve

m anufacturability and tracking

2. No changes to wall thickness Effective for SB6

- 2 through 11/09. No change in exhaust side exterior wall

contourReport 1102

- 13

Page 8 Dwg No. Rev Date Chang es/Adjustments Comments

J 12/03/09 Added material to fuel injector boss to

minimize cracking in this area 1. Rev. G, H not produced

2. No change in exhaust side exterior
wall contour

3. Introduced 1/10



### Table 1B. AEC6541 5 Head Machining

Dwg No. Rev Date Changes/Adjustments Comments

AEC65415 IR 3/7/03 R e drawn from AEC65385 Rev. C No effect on cylinder interface or head
cracks

A 5/3/05 Minor adjustments No effect on cylinder interface or head
cracks

B 3/3/06 Minor adjustments No effect on cylinder interface or head
cracks

C 3/ 19 /07 Minor adjustments No effect on cylinder interface or head
cracks

D 7/11 /08 Reinstated Allison style back intake valve seat

configuration 1. Increas e wall thickness on intake valve side of cylinder head.

2. Implemented in 10/08

E 9/ 23 /09 Minor change to notes No effect on cylinder interface or head
cracks



### Table 1C. AE65041 Choke Configuration

Dwg No. Rev Date Characteristic Cylinder ID (Dia F) (in) Changes/Adjustments Comments

AE65041 F Bench mark 5.2530
5.2510 1. Effective drawing on 8/29/02

2. Use for establishing nominal I D of barrel No effect on cylinder interface

G 9/27/02 5.2530

5.2510 Minor changes No effect on cylinder interface

H 8/1/05 5.2530

5.2510 Minor changes No effect on cylinder interface

J 11/30/06 5.2530

5.2510 Minor changes No effect on cylinder interface

K 2/28/07 5.2530

5.2510 Minor changes No effect on cylinder interface



### Table 1D. AEC631399 Cylinder Head Thread and Pilot Diameters

Dwg No. Rev Date Interference (in) Dome F illet

R ad. (in) J

- Head Pitch

Max . Dia. (in) J

- Head Pitch

Min . Dia. (in) H

- Head

Band Max

. Dia. (in) H

- Head

Band Min

. Dia. (in)

AEC63199 G 2/1 /200 1 >= 0.007 .025

- .035 5.554 5.552 5.459 5.457

H 1 2 / 2 /2003 >= 0.007 .025

- .035 5.554 5.552 5.459 5.457

J 3/ 1 7/2004 .009

- .014 .040

- .050 5.554 5.552 5.459 5.457Report 1102

- 13

Page 9 Dwg No. Rev Date Interference (in) Dome F illet

R ad. (in) J

- Head Pitch

Max . Dia. (in) J

- Head Pitch

Min . Dia. (in) H

- Head

Band Max

. Dia. (in) H

- Head

Band Min

. Dia. (in)

K 3/2 5 /2005 .009

- .014 .040

- .050 5.554 5.552 5.459 5.457

L 1/ 23 /2007 .009

- .014 .040

- .050 5.554 5.552 5.459 5.457

M 3 /1 1 /2009 Up to 0.020 .045

- .055 5.552 5.550 5.455 5.453

N 8/1 8 /2009 Up to 0.020 .045

- .055 5.552 5.550 5.453 5.451



### Notes to Table 1D:

1. Dome fillet radius in the clearance a r ea was set at 0.03

- inch nominal through 11/05.

2. Revision K implemented in 11/05 introduced a larger fillet radius.

3. Revision H through L retained same shrink band and thread diameters establishing the
interference levels shown.

4. Revision N implemented 10/13/09 adjusted the shrink band and thread diameters to increase
interference fit.



### Table 1E. AEC634501 Barrel, Cylinder 5.25

- inch Bore

Dwg No. Rev Date Interference (in) X

- Barrel Pitch

Max . Dia. (in) X

- Barrel Pitch

Min . Dia (in) Y

- Barrel Band

Max . Dia. (in) Y

- Barrel Band

Min . Dia. (in)

AEC634501 N 2 / 28 /2002 .009

- .014 5.566 5.563 5.471 5.468

P 1/ 22 /200 4 .009

- .014 5.566 5.563 5.471 5.468

R 4 / 28 /2004 .009

- .014 5.566 5.563 5.471 5.468

T 6/27/2005 .009

- .014 5.566 5.563 5.471 5.468

U 11/ 10 /2005 .009

- .014 5.566 5.563 5.471 5.468

V 3 / 23 /200 6 .009

- .014 5.566 5.563 5.471 5.468



### Notes to Table 1E:

1. Barrel thread pitch diameter and shrink band diameter have not changed throughout the production run from 8/29/2002 through 12/31/2010.

Examination of Table 1 shows AE addressed three significant issues affecting cylinder cracking. First

, AE introduced AEC65385 Revision E with increa sed wall thickness on the exhaus t port side to prevent thermal fatigue cracks associated with these areas identified by MSB6

- 2. Later AE introduced

AEC65385 Revision J to address observations of cracks in the fuel injector b oss found during overhaul of cylinders 4

.

Second AE adjusted AEC631399 thread and pilot dimensions to increase the shrink band to dome fillet
radius in the clearance area between the barrel shrink band and cylinder head, implemented in
November 2005.

Thir d, AE adjusted AEC631399 to increase the inter ference fit , implemented in October 2009 . As our analysis will demonstrate, the latter changes had significant effect on the integrity of the head

- barrel
interface area

.Report 1102

- 13

Page 10 Table 2 summarizes applicable mandatory service bulletins that resulted in service removals or warranty rework.

TABLE 2 . SUMMARY OF SERV I CE BULLETINS

Group From To SN Start SN End Description Issue

MSB4

- 1 9/1/2002 5/12/2003 1 7708 1. Sporadic deviation occurred from approved
heat treatment

2. Cracks could occur at fin 9 or 10 counting
from shrink band. Remove from service for inspection 3/1/2004

MSB6

- 2 5/13/2003 11/ 29 /2005 7709 33696 1. Inspect cylinders for cracks that may lead to loss of compression

2. Recurring inspections each 50 hours starting
at 500 hours

3. Cracks associated with 7th fin from bottom
of head on exhaust side 8/25/2006



### Notes to Table 2:

1. The FAA issued AD2004

- 08

- 10 to insure compliance with MSB4

- 1.

The se drawings and service bulletins form the basis for segregating the cylinder assembly population
into sub

- groups aligned with service bulletins and drawing configurations . Thus, we have:

1. G roup SB4

- 1 (4

- 1) , cylinders produced affected by the mandatory service bulletin to inspect or replace cylinders that did not receive proper heat treatment.

2. Group SB6

- 2 (6

- 2) , cylinders produced affected by the mandatory service bulletin of repetitive inspe ctions for wall cracks.

3. Group Post SB6

- 2 (P6

- 2) , cylinders produced from a head casting with greater wall thickness, including assemblies incorporating the Allison style back on the intake valve seat

4. Group Post SB6

- 2

- INT

- A (P6

- 2INT

- A) , cylinders produced w ith thicker walled head castings and incorporating improved interference fit with Allison style back ed intake valve seats

Table 3 summarizes pertinent identification and configuration information for each identified population group.

TABLE 3 . IDENTIFIED AEC631 397 CYLINDER POPULAT ION GROUPS

Group From To SN Start SN End AEC65385
Head AEC631399

Head

T hreads AEC634501

Barrel AEC6 5414

Head Machining

MSB4

- 1 9/1/2002 5/12/2003 1 7708 C G N IR, A

MSB6

- 2 5/13/2003 11/ 29 /2005 7709 33696 D H N, P, R, T, AReport 1102

- 13

Page 11 Post 6

- 2 10 / 26 /2005 10/12/2009 33745

- 01 64016

- 22 E, F K, L U , V C, D

P6

- 2INT

- A 10/13/2009 Current 64016

- 23 Current F, J N V E



### Notes to Table 3:

1. The shrink band diameter, shrink band length, thread pitch diameter, and thread pitch length
shown in AEC634501 remain constant over the production run

. 2. AEC65385 Rev. E introduced increased wall thickness on the exhaust side.
3. AEC631399 Rev. K introduced an in creased head shrink band to dome transition radius.

4. AEC631399 Rev. N introduced an increased interference fit.

5. Allison back ed intake valve seats to increase wall thickness were introduced with AEC65414

Rev. D.
6. Characteristic cylinder barrel inside diameter defined by AE65041 did not change over the production run.



## Production and Warranty Data

AE provided production run dat a that included ship date, class, and serial number. Separately

, AE provided a listing of warranty returns. We cross referenced the warranty returns against the production run

, and relocated warranty matched units to a separate listing for each for each identified cylinder population. S ubsequent statistical analysis included failed cylinders and all c ylinders not reported as failed or removed from service by warranty action

. Based on shipping date and a simple conversion from the recognized standard annual aircraft use rate of 100 hours/per year to hours per day, we c omputed days in service and accumulated hours for each cylinder in service. For known failures

, we used the reported time in service.

The size of the lists for each population necessitated placing this data into four supplements, 1 through 4, correspondin g to each of the identified population groups:

1. Group SB4

- 1 (4

- 1)

2. Group SB6

- 2 (6

- 2 )

3. Group Post SB6

- 2 (P6

- 2)

4. Group Post SB6

- 2

- INT

- A (P6

- 2INT

- A)

Certain policies and procedures in use by AE to manage production and traditional warranty claims
have introduced a degree of uncertainty into product tracking. AE and its Precision Machined Airparts
affiliate assign serial numbers to each cylinder head as well as the cylinder barrel. Field tracking uses
the cylinder head number. However, Airparts controls plant wo rkflow by work order , with component inventory withdrawals for assembly on a first in

- first out basis by lot and not by serial number. This
introduces an out of sequence serial number progression at assembly resulting in shipping dates not fully synchro nized with serial numbers. This mismatch adds a degree of complexity in determining
date ranges for design changes or service bulletins. Field technicians or quality personnel require both dates and serial numbers to determine the status of a particular unit.Report 1102

- 13

Page 12 Another issue stems from traditional tracking of repair station services , which affects utility of warranty data. Engine Components assigns a new serial number to all units returned for warranty work or repair station work. While this allows the re pair station to track its work, identifying the underlying originally manufactured unit is impractical unless the customer service staff specifically records incoming the serial number as part of a mandatory service bulletin or AD action. In this study

wa rranty data clearly identified cylinders affected by MSB6

- 2 and a smaller number of cylinders assigned to the Post MSB6

- 2 population. We found no alignment in the warranty data to the other groups. However, the warranty data did identify some cylinders i ncluded as failed units in the FAA's
MDR database.

With the exception of g roup SB6

- 2, we must recognize some degree of uncertainty on the remaining numbers of units in the field. This uncertainty causes a small overstatement of field suspensions (in

servi ce units) for groups Post SB6

- 2 and Post SB6

- 2

- INT

- A, but it creates a major uncertainty for those
units identified as belonging to g roup SB4

- 1. MSB4

- 1 addressed a heat treatment condition. All reported head

- barrel separations occurred in 2003. The pr oduction records show over 2,500 units still in service, which suggests a batch problem. However, the inherent design of cylinders in this population matches that of g roup MSB6

- 2 suggesting that head barrel separations should have occurred after year 2003 . In this case, we confront two possibilities:

1. MSB4

- 1 removed the cylinders prone to failure from the population.

2. MSB4

- 1 removed all cylinders from this population.

The author believes most, but not all of the cylinders associated with MSB4

- 1 have been wi thdrawn
from service because one cylinder associated with the MSB4

- 1 population appeared in AE files with a reported separation date of 12/2/2008. Based on design configuration, any remaining cylinders in this population will have characteristics similar to the SB6

- 2 population group. In fact, MSB6

- 2 includes those units covered by MSB4

- 1

. However, the degree of uncertainty associated with the SB4

- 1 population suspensions argue against adding these suspensions to the SB6

- 2 population suspensions.

With re spect to g roup Post MSB6

- 2 and g roup Post MSB6

- 2

- INT

- A
, we must assume all units not failed

, or identified specifically in warranty reports

, remain in the field. Given these issues, the author strongly recommends assigning a sequential serial number to each cylinder assembly

, and other products that directly affect operational safety

, at the point of shipping. E ach tracking serial number
would link to a product management database with complete information for each serialized unit on
the sub

- components used in manufacture, process records, and service information. This system would lead to prompt identification and resolution of continued operation safety issues as they may
arise.

Traceability issues notwithstanding , Table 4 summarizes pertinent inform ation relating to the population of each identified cylinder group.Report 1102

- 13

Page 13 TABLE 4 . CYLINDER GROUP PO PULATIONS

- SUMMARY OF DATA

Group Qty

Produced Basic

Configuration Base +

Allison Style
Intake Valve
Seat Back Improved

Interference + Allison Style
Intake Valve
Seat Back Failures Warranty
Removals Net in

Service

4

- 1 2,572 2,572 0 0 4 0 2,5 6 8

6

- 2 13,615 13,615 0 0 21 756 12,838

P6

- 2 20,93 7 16,43 6 4,501 0 8 40 20,8 8 9

P6

- 2

- INT

- A 6,643 0 0 6,643 0 0 6,643

Totals 43,76 7 32,62 3 4,501 6,643 3 3 796 42,9 3 8



## Visual Examination

We conducted a visual assessment of cylinders in storage at AE that experienced head

- barrel separation in parallel with the statistical evaluation. Visually, we observed three failure modes:

1. Fatigue failure of the first loaded head thread

2. Fatigue failure in the head clearance area for the barrel at fillet transition between the shrink
band and the dome
3. Stripped threads associated with some repaired cylinders

Knowing the existence of multiple failure modes, we would expect generally poor fits of consolidated separation data associated with each population. Indeed, the statistical assessment of consolidated separation data presented later shows a classical pattern of multiple failure modes.

Figure 1 illustrates the th read fatigue failure. Externally, the position of the first loaded thread falls between fins 5 through 7 counting from the bottom of the cylinder head. Cylinder SN33947

- 29 illustrated in Figure 1 shows the classic striation pattern for fatigue over about 40% of the cross section area before final failure occurred from overload. Notice the transition fillet radius is separated from the thread by the shrink band.Report 1102

- 13

Page 14 FIGURE 1 . CYLINDER ASSEMBLY SN33947

- 29 , THREAD FAILURE

Figure 2 illustrates the radius fatigue failure. Externally, the position of the fillet radius between fins 9 and 10 counting from the bottom of the cylinder head. MSB4

- 1 specifically instructs the aviation maintenance technician to examine this region of the head for cracks. Referring to Table 1D we find drawing AE631399 Rev. H calls out a 0.025

- 0.035

- inch radius. Based on production data, AE used this version of the cylinder thread and pilot diameter drawing for cylinders shipped from 8/29/02 through 11/29/05. Beginning with cylinder serial number 33745

- 01 shipped on 10/26/05, AE incorporate d at
least a 0.040

- inch radius in the fillet. Supported by visual observation, statistical review confirms that increasing the fillet radius eliminated this failure. Therefore, we conclude that population groups SB4

- 1 and SB6

- 2 would have exposure to thr ead fatigue and radius fatigue modes

. The head

- barrel interface in p opulation group Post SB6

- 2 has exposure only to the head thread fatigue failure mode

.
Qualitatively, failures in the head transition fillet show a smaller fatigue striation area with a much coarser striation pattern than the thread fatigue failure illustrated in Figure 1. This justifies statistically attempting to create separate cumulative failure distributions for each failure mode. FATIGU E ORIGIN

SHRINK BAND

FILLET RADIUSReport 1102

- 13

Page 15 FIGURE 2 . CYLINDER ASSEMBL Y SN23217

- 13 , RADIUS FAILURE

In stripped thread failures

, the threads incurred severe mechanical damage from the extensive relative
motion between the head and barrel. Other than gross thread damage, the head and barrel remain

intact . More subtlet y, this failure mode suggests the threads will not withstand the operational loads
in the absence of interference between the head and barrel.



## Summary Listing of Separated Cylinders

Table 4 lists all traceable cylinder failures . When known, we listed the location of the failure and identified the applicable population group.

FATIGUE AREA FILLET RADIUSReport 1102

- 13

Page 16 TABLE 5 . CONSOLIDATED LIST ING OF AEC631397 HEA D BARREL SEPARATIONS

S/N Type Class Engine Shipped Reported/
Removed TIS

(hrs) Fa ilure
Location AEC631399

Rev. Level FAA MDR ID MSB

4464

- 24 TIST 71.2A IO

- 520F 1/20/2003 3/31/2003 87 d ome radius G

- H CY42003F00000 4

- 1

4360

- 32 TIST 71.2B TSIO

- 520 1/15/2003 12/2/2008 218.1 dome
radius G

- H 4

- 1

5482

- 19 TIST 71.2A 2/14/2003 9/3/2003 283 G

- H 4

- 1

7141

- 16 TIST 71.2A 4/14/2003 11/15/2003 269 G

- H 4

- 1

7819

- 23 TISN 71.2B TSIO

- 520NB 5/23/2003 4/23/2004 204 H BHA05RS 6

- 2

8013

- 28 TIS N 71.2B 5/19/2003 8/12/2009 960 dome
radius H MT2 6

- 2

12612

- 5 TISN 71.2B TSIO

- 520NB 10/10/2003 4/28/2004 200 H BIER200401060 6

- 2

13515

- 11 TISN 71.2B TSIO520

- NB 1/5/2004 6/15/2010 360 thread H 6

- 2

13515

- 26 TISN 76.0 IO

- 550D 2/5/2004 8/12/2008 338 thread H 6

- 2

13670

- 3 TISN 71.2C 1/22/2004 4/18/2006 1301 H 2006FA0000455 6

- 2

16757

- 6 TISN 71.2B TSIO

- 520NB 4/1/2004 3/18/2005 475 H 2005FA0000427 6

- 2

18700

- 1 TIS N 71.2A IO

- 55F 6/17/2004 5/1/2009 663 thread H MTPH

- 1 6

- 2

19441

- 28 TISN 71.2A IO

- 520D 7/23/2004 6/5/2007 290 H MTPH

- 10 6

- 2

20940

- 22 TISN 76.0 IO

- 550F 8/19/2004 12/12/2005 89 H AU510001488 6

- 2

21327

- 19 TISN 71.2B TSIO

- 520 9/10/2004 2/7/2005 721 H MTPH

- 7 6

- 2

21432

- 10 TISN 71.2C IO

- 550C 8/31/2004 10/14/2008 355 dome
radius H 2008FA0000681 6

- 2

21994

- 21 TISN 71.2B TSIO

- 520NB 9/16/2004 5/11/2006 330 H 2006FA0000498 6

- 2

21590

- 14 TISN 71.2C IO

- 550B 9/10/2004 4/27/2009 150 dome
radius H MTPH

- 2 6

- 2

22241

- 24 TISN 71.2B TSIO

- 520NB 10/11/2004 7/14/2010 264 H MTPH

- 11 6

- 2

22389

- 9 TISN 71.2B IO

- 550B 10/5/2004 5/3/2006 170.2 H MT1

- 2006FA0000489 6

- 2

22537

- 24 TISN 71.2B IO

- 550B 10/5/2004 5/3/2006 171.7 H 2006FA0000489 6

- 2

22838

- 19 TISN 71.2B TSIO

- 520WB 10/20/2004 3/11/2009 390 dome
radius H MTPH

- 5 6

- 2

23217

- 13 TISN 71.2B TSIO

- 520NB 10/19/2004 12/30/2008 257 dome
radius H 6

- 2

23343

- 15 TISN 71.2B 10/26/2004 8/1/2005 505 H MTPH

- 8 6

- 2

23258

- 14 TISN 71.2B TSIO

- 520 11/1/2004 5/18/2008 423.9 dome
radius H 6

- 2

33947

- 29 TISN 71.2C IO

- 550B 11/22/2005 11/20/2008 210 thread J

- K

- L p6

- 2Report 1102

- 13

Page 17 S/N Type Class Engine Shipped Reported/
Removed TIS

(hrs) Fa ilure
Location AEC631399

Rev. Level FAA MDR ID MSB

34684

- 13 TISN 71.2C IO

- 550A 11/6/2005 10/1/2010 1061 J

- K

- L MT5 p6

- 2

35955

- 22 TISN 71.2B TSIO

- 520NB 1/6/2006 5/20/2009 1163 thread J

- K

- L J7B2009F00000 p6

- 2

45312

- 15 TISN 71. 2 TSIO

- 520WB 3/2/2007 9/12/2009 1095 thread J

- K

- L p6

- 2

50785

- 26 TISN 71.3 B TSIO

- 520WB 11/20/2007 4/3/2009 196 thread J

- K

- L p6

- 2

51847

- 12 TISN 71.2B TSIO

- 520 1/23/2008 7/30/2010 71.2 thread J

- K

- L p6

- 2

51973

- 08 TISN 71.2B TSIO

- 520 1/28/2008 8/4/2009 835 J

- K

- L MT4 P6

- 2

52884

- 22 TISN 76.0 IO

- 550F 6/4/2008 11/13/2008 415.8 thread J

- K

- L p6

- 2

Total 3 3

MSB4

- 1 4

MSB6

- 2 21

Post MSB6

- 2 8

Examination of Table 5 leads to several observations relevant to head

- barrel separations:

1. No particular engine model has a pronounced tendency for incurring head

- barrel separations.

2. Direct visual observation confirmed two failure modes associated with the head

- barrel interface, fatigue failure in the first loaded thread and fatigue failure in the shrink band to
dom e transition radius.

3. Increasing the head shrink band to dome transition radius beginning with AEC631399 Rev. J eliminated fatigue failures in the head shrink band to dome transition radius.

4. Of the four head

- barrel separations associated with the serial num ber range covered by MSB4

- 1
, one failure occurred in December 2008, and confirmed as a dome radius failure.

With reference to separations associated with MSB4

- 1
, we recall that some portion of this population
did not receive the correct heat treatment afte r the casting process. The bulletin requires inspectors to pay particular attention to cracks located at fin 9 or 10 counting from the bottom of the head, which corresponds to cracks at the head shrink band to dome transition fillet. However, this instru ction does not preclude the possibility that other failure modes may be in operation. If so, improper heat treatment would exacerbate these tendencies and foreshorten the fatigue life of cylinder assemblies prone to any particular failure mode.

In an effort to provide a better basis for analysis, Mr. Pete Hakala, Propulsion Engineer, FAA ASW

- 190, forwarded failure information on cylinders associated with MSB4

- 1 5 . Table 6 extracts data from the information provided. Attachment 1 contains to complete c ontent of the information provided.Report 1102

- 13

Page 18 TABLE 6 . FAA MDR LISTING A EC631397 SEPARATIONS AS OF 1/13/04

Date A/C Model Engine Horsepower C yl No. TIS (hrs)

2/21/2003 C414A TSIO

- 520NB 335 6 45
4/3/2003 C340A TSIO

- 520NB 335 6 100
4/9/2003 C414 TSIO

- 520NB 335 2 100
4/14/2003 C310R TSIO

- 520EB 300 6 100
4/14/2003 C414 TSIO

- 520NB 335 6 80
4/15/2003 C340A TSIO

- 520NB 335 6 70
4/24/2003 C402C TSIO

- 520VB 325 6 193
5/2/2003 C414A TSIO

- 520NB 335 6 70
5/28/2003 C414A TSIO

- 520NB 335 6 100
6/10/2003 C340A TSIO

- 520NB 335 6 64.9
6/13/2003 C414A TSIO

- 520NB 335 6 177
6/20/2003 C414A TSIO

- 520NB 335 6 177
6/24/2003 C340A TSIO

- 520NB 335 6 113.7
6/29/2003 C340A TSIO

- 520NB 335 6 78
7/2/2003 C402C TSIO

- 520VB 325 6 348.7
7/5/2003 C414A TSIO

- 520NB 335 2 100
7/7/2003 C414 TSIO

- 520NB 335 6 107
7/14/2003 C340A TSIO

- 520NB 335 4 64.9
7/16/2003 C310R TSIO

- 520EB 300 6 200
7/17/2003 C414A TSIO

- 520NB 335 6 102
7/23/2003 C340A TSIO

- 520NB 335 2 116
7/25/2003 C414 TSIO

- 520NB 335 6 150
7/29/2003 C340A TSIO

- 520NB 335 6 125
8/20/2003 C402C TSIO

- 520VB 325 3 373
10/1/2003 C402C TSIO

- 520VB 325 1 580
10/30/2003 C340A TSIO

- 520NB 335 4 208.6
11/4/2003 C414A TSIO

- 520NB 325 2 120
11/7/2003 C340A TSIO

- 520NB 335 1 191.2
11/12/2003 A36 IO

- 550B 300 6 150.3
11/20/2003 C414 TSIO

- 520NB 335 2 100
11/24/2003 C340A TSIO

- 520NB 335 2 122

Total 31
Count Cyl. 6 20Report 1102

- 13

Page 19 Table 6 lists 31 additional failures, all with time in service less than 6 00 hours , which is consistent with
the four additional units listed in Table 5. This report suggests cylinder 6 as the most troublesome, which strongly indicates installation configuration, cooling baffles, and operational patterns will affect statistical results. The data infer that cylinders exp eriencing head

- barrel separations after 12/31/03
had the correct heat treatment

, or were not removed as part of the MSB4

- 1 program. The information available does not permit us to distinguish which condition holds. Therefore, our treatment will

assume MS B4

- 1 suspensions remain in the field and that 35 failures have occurred in this group, with one reported in late 2008. Unfortunately, this may distort the actual distribution because the late 2008 failure implies many late suspensions.

Population group SB 6

- 2 will require consideration for multiple failure modes. However, the correct heat treatment increased the fatigue resistance of the machined head, which reduced the frequency of premature failures. For population group Post SB6

- 2
, we need only consider one failure mode, fatigue
of the first loaded thread.

Table 7 summarizes reported cylinder separations not traceable to the production listings. Of the five reported with unknown serial numbers, one is associated with a TCM 470 seri es engine, which this study does not address. Four cylinders were confirmed or probable repaired units. Three experienced stripped threads. As with new production cylinders, we recommend establishing a post repair tracking system that retains reference to the original manufacturer's serial number . Statistically, we will create a cumulative failure distribution for the stripped thread failure mode to establish a baseline characterization. However, without information regarding the number of units servic ed or the numbers still in service after the last depot visit, we cannot adjust the base curve to reflect the active suspensions.

TABLE 7 . AEC631397 HEAD

- BARREL SEPARATIONS NOT TRACEABLE TO THE PRODUCTION LISTS

S/N Type Class Engine Shipped Reported/
Removed TIS Failure

Location AEC631399

Rev. Level FAA MDR ID/Notes MSB

8009

- 00 FRST 71.2C IO

- 550B 12/2/2003 1/11/2005 409 stripped
threads H 2005FA0000117/

Freedom cylinder NA

17029

- 28 CC CN 71.2B TSIO

- 520

- NB 4/19/2004 10/28/2009 267 stripped
threads H MTPH

- 4/Freedom NA

31265

- 20 TISN 71.2B IO

- 520C 7/27/2005 6/15/2009 417 stripped
threads H MTPH

- 3/Freedom NA

32803

- 1 TISN 71.2B TSIO

- 520M 9/12/2009 1095 H OW62009F00000/
Probable Freedom NA

47932

- 06 TISN 71.2B TSIO

- 520VB 7/27/2007 10/15/2010 1254 NA K MT

- 6/ Repaired NA

9138

- 00 TISN 71.2A IO

- 520 4/6/2005 1787 H MTPH

- 9 NA

UNK

- 1 TISN 71.2B TSIO

- 520NB 2/23/2010 421 ? 2010FA0000179 NAReport 1102

- 13

Page 20 S/N Type Class Engine Shipped Reported/
Removed TIS Failure

Location AEC631399

Rev. Level FAA MDR ID/Notes MSB

UNK

- 2 TISN 71.2B TSIO

- 520N 3/12/2008 105 ? CA080410009 NA

UNK

- 3 O

- 470R 2/18/2010 151 ? CA100218008 NA

UNK

-- 5 TISN 71.2A IO

- 520F 6/21/2005 489 H FXT2005F00000 NA

Total 10

The TCM 520/550 engines power aircraft used in charter, cargo, and contracted utility work. For these aircraft, the generally accepted use rate of 100 flight hours per year for general aviation aircraft may not be valid. Table 5 provides a sample basis t o test this assumption. Table 8 takes data from Table 5 and computes the standard use hours (STD Hrs) based on shipping and removal dates for each traceable cylinder with a confirmed head

- barrel separation. For the individual distributions of reported time in service hours and standard hours, the coefficient of variation (standard deviation/mean) suggests significant scatter in each. The relationship of time in service (TIS) to STD Hrs suggest a ratio of about 3/1, but the coefficient of variation exce eds 1, indicating an invalid correlation caused by widely scattered data as shown in Figure 3. The graph shows a weak positive relationship with extensive scatter, negating any value in using a modifier to adjust in service suspension times for each popul ation.

TABLE 8 . SAMPLE POPULATION USED FOR EVALUATING A POTENTIAL TIS/STD HRS RELATIONSHIP

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 0.68Report 1102

- 13

Page 21 S/N Group Shipped Removed TIS (Hrs) STD () Hrs TIS/STD

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

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 1.21Report 1102

- 13

Page 22 FIGURE 3

. PLOTTED TIS/STD HRS DATA



## Statistical Assessment

Cylinder Population Group MSB4

- 1
We begin our statistical analysis with the combined population group 4

- 1 separation data from Tables 5 and 6. The consolidated data illustrated in Figure 4 indicates multiple modes. Abernethy's software program (Ref. 1) suggested insufficient data to spl it the data into two curves. Subsequently, we manually split the data into three separate curves, and obtained good data fits as illustrated in Figure

5 . This suggests the reported failures include some or all of the previously identified failure modes:

1. Fatigue failure of the first loaded head thread

2. Fatigue failure in the fillet radius at the head shrink band to dome clearance transition

3. Stripped head threads of repaired cylinders. 

## 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 

# Time in Service

- Standard Hour RelationshipReport 1102

- 13

Page 23 FIGURE 4 . GROUP SB4

- 1 CONSOLIDATED DISTR IBUTION OF REPORTED SEPARATIONS

Segregating the reported separations into three distributions resulted in excellent data fits. If we assume the listing of separated cylinders do not include repaired cylinders with stripped threads

, we can explain the three cumulative distributions in terms of the incorrect heat treatment identified in

MSB4

- 1. At the time of MSB4

- 1 publication, customers would have returned very few cylinder
assemblies attributed to AE manufacture t o the EC Services repair station. This would make it highly unlikely that Mode 1 failure identified in Figure 5 would represent a cumulative failure distribution for stripped threads. Thus, we can deduce the Mode 1 failure mode most likely represents fat igue cracks in the dome transition radius of those cylinders identified in MSB4

- 1 that did not receive the correct
heat treatment.

The Mode 2 failure distribution identified in Figure 5 would represent a cumulative failure distribution for those cylinder s correctly heat treated that manifest a fatigue crack in the dome fillet radius. The Mode 3 distribution would represent correc tly heat treated cylinders experiencing fatigue cracks in the first loaded thread. The slope of this distribution is consisten t with that identified in Ref. 2 for AEL65102 cylinders separating by propagation of a fatigue crack in the first loaded thread.

Table 9 provides the summary of data points used for each distribution. The small number of data points permitted manual estim ation of the groupings. Any effort to improve the fit of Mode 1 by distributing data points to the other modes resulted in severely degraded curve fit quality indicated by

a pve well below 10%. A s defined by Abernethy (Ref. 1)

, pve is the percentile rank of the correlationReport 1102

- 13

Page 24 coefficient against all possible correlation coefficients. By experience and demonstration, pve ranks of at least 10% indicate acceptable data fit.

FIGURE 5 . GROUP SB 4

- 1 SEGREGATED DISTRIB UTIONS FOR THE REPORT ED SEPARATIONS

TABLE 9 . DATA POINTS FROM FIGURE 4 ASSIGNED TO IDENTIFIED FAILURE M ODES

Time in Service (hours)

Mode 1 Mode 2 Mode 3

45 100 150 150.3

70 100 177 269

70 102 177 283

78 107 191.2 348.7

80 113.7 193 373

87 116 200 580

100 120 208.6

100 122 218.1

100 125

100Report 1102

- 13

Page 25 Building upon the analysis of the separation data of group 4

- 1 without the suspension, we examine the effect of suspension s on the cumulative failure distribution . For this analysis, we will present consolidated data including the FAA supplied information less the separations presumed associated
with head fillet failures attributable to incorrect heat treatment as noted in MSB4

- 1 . Next, we will segregate the sepa ration presumed associated with thread failures and failures in the head transition
radius.

Figure 6 presents the adjusted consolidated data for population group 4

- 1 using the suspension data given in Report 1102

- 13 Supplement 1 without any adjustment to the computed standard hours in

service . Notice the curve clearly shows a multiple failure mode pattern. Figure 7 presents g roup SB 4

- 1 cumulative distribution frequency curves for Mode 2 and Mode 3 failures by separately combining the presumed in

- service suspensions with Mode 2 and Mode 3 data points.

Table 10 offers a statistical summary of the data presented in Figure 7. Statistically, as indicated by pve
and the correlat ion coefficients

, the data has a good fit to the presented cumulative distributi on functions

. F atigue fractures in the dome fillet radius shown by the Mode 2 curve would normally represent a serious concern. However, nearly all reported failures for this population occurred in 2003. Figure 6 indicates a batch problem and an underly ing failure mode. In this case

, the batch problem would represent the fatigue fracture of the dome fillet radius. Further, w e can infer that cylinders produced at the low end of the established fillet radius tolerance of 0.035/0.025

- inch would have a gre ater propensity for initiation of a fatigue crack than those produced at the upper end of the
tolera nce band. By 12/31/2010, service bulletin action and field experience should have removed the cylinders in this population most likely to experience fatigu e cracking in the dome fillet radius. MSB4

- 1 require d removal of cylinders most likely to experience this failure mode, and given that the standard fleet hours accumulated by this population now exceed the characteristic life of about 485 hours for correctly heat treated cylinders exhibiting this failure mode, we can reasonably conclude nearly all of the cylinders that would have a tendency for fillet radius fatigue have been removed from the population. The 2003 dates for the vast majority of the r eported dates of head

- barrel separations for this population supports this conclusion. No further action for this failure mode in population group 4

- 1 is necessary.

The underlying failure mode distributed in the population would be the fatigue fracture of the first loaded thread. This makes sense from an engineering standpoint because the separation data shows
that incre a sing the fillet radius greatly reduces any propensity for fatigue fracture in the dome fillet
radius . Cylinders in the group SB4

- 1 popu lation produced with an interference fit set near the design
minimum would have an increased risk of thread failure in service depending on actual interference and engine operating conditions. The p opulation of group SB 4

- 1
, not affected by MSB4

- 1
, falls u nder
the requirements of MSB6

- 2 . This bulletin requires continuing inspections for head cracks. These inspections should provide some early warning detection of thread cracks in the remaining population.Report 1102

- 13

Page 26 FIGURE 6 . GROUP SB 4

- 1 WITH SUSPENSIONS ADJ SUTED TO REMOVE MODE 1 SEPARATIONS

FIGURE 7 . GROUP SB 4

- 1 WITH SUSPENSIONS, SEGREGATED MODESReport 1102

- 13

Page 27 TABLE 10 . STATISITCAL SUMAM RY OF WEIBULL DATA F OR CYLIDNER GROUP SB 4

- 1

Mode Points Susp. r r 2 ccc 2 pve % η (hrs) β B times (hrs)

1% 2% 5%

2 2576 2568 0.9798 0.960 0.8425 77.44 484.6 7.023 251.7 278 317.5

3 257 4 2568 0.9656 0.915 0.8203 44.23 13,724 1.816 1,090 1,601 2,674

Table 11 and Figure 8 presents results of the risk projection for thread fatigue separation (Mode 3) using software from Reference 1, assuming only half the suspensions remain in the field and a use rate of 8.333 hours per month. The analysis projects ten additional failures over the next sixty months

. We suggest reducing risk by removing these cylinders from service at the next engine tear down or
schedule d overhaul interval , whichever comes first.

TABLE 11 . RISK PROJECTION T HREA D FATIGUE FAILURES F OR CYLINDER GROUP SB 4

- 1Report 1102

- 13

Page 28 FIGURE 8 . GRPAHICAL PROJECT ION OF PROJECTED SEP ARATIONS FOR GROUP SB 4

- 1



### Population Group SB6

- 2
Figure 9 shows the consolidated Weibull plot derived from Table 5 for reported head

- barrel separations on cylinders with serial numbers associated with group SB6

- 2. Although the curve fit pve of about 24% suggests an adequate fit, we know f r om direct observation that two separation modes are active within this population, fatigue cracking at cylinder head shrink band to dome fillet radius and fatigue cracking in the first loaded thread.

Figure 10 displays the consolidated Weibull cumulative distributi on function (CDF) for the entire population based on the production data contained in Report 1102

- 13 Supplement 2. Adding the suspensions degrades the curve fit as shown by a pve below 1% and exacerbates the effect of the multiple failure modes in play. As expected the consolidated CDF for group SB6

- 2 with suspensions closely resembles the consolidated CDF for group SB4

- 1 with suspensions shown in Figure 6.Report 1102

- 13

Page 29 FIGURE 9 . GROUP SB6

- 2 CONSOLIDATED DISTR IBUTION OF REPORTED SEPARATIONS

FIGURE 10 . GROUP SB 6

- 2 WITH SUSPENSIONSReport 1102

- 13

Page 30 Figure 11 and Table 12 shows the results of splitting data points into two CDFs. These curves were created by manual iteration starting from Table 5 and assigning know n dome radius s eparations into a separate distribution from those separations as identified or presumed thread fatigue failures. We next added suspension data from Report 1102

- 13 Supplement 2 to each CDF obtaining preliminary

curves. B a sed on examination of the curves, we shifted cylinder serial number 13670

- 3 from the thread failure group to the radius failure group, obtaining the CDF's displayed. Mode 1 represents the
CDF for the dome radius, fatigue crack separation mode

, and Mode 2 represents the CDF for the
thread fatigue separation mode. As shown in Table 13, t he slope s of both curves are very consistent with the CDF's generated for g roup SB 4

- 1 , affirming the validity of the analysis

.

FIGURE 11 . GROUP SB 6

- 2 WITH SUSPENSIONS, SEGREGATED MODES

TABLE 12 . STATISITCAL SUMAM RY OF WEIBULL DATA F OR CYLIDNER GROUP SB 6

- 2

Mode Points Susp. r r 2 ccc 2 pve % η (hrs) β B times (hrs)

1% 2% 5%

1 1283 4 12827 0. 9418 0. 887 0.8 325 26.15 1,2 68 5. 853 578 651 763

2 1285 1 128 3 7 0.9 664 0. 934 0. 8829 35.31 35,947 1.6 0 4 2, 041 3, 155 5
, 640Report 1102

- 13

Page 31 TABLE 13 . CHARACTERISTIC VA LUE COMPARISON OF CD F PLOTS FOR GROUPS SB 4

- 1 AND SB 6

- 2

Group Dome Radius Failure Head Thread Failure

Beta Eta (hours) Beta Eta (hours)

4

- 1 7.023 484.6 1.816 13,724

6

- 2 5. 853 1,2 68 1.6 0 4 3 5
, 947

The potential for dome radius cracks complicates the assessment of risk. We must determine whether the potential for dome radius cracking represents a significant risk. Examining the data from Report

1102

- 3 Supplement 2 we find the for cylinders in this group manufactured in November 2005, the standard time in service projection of about 509 hours correspond to a cumulative failure of 0.48%. A B time of 2% corresponds to about 650 hours in service. However, using the Abernethy Risk Assessment (Ref. 1) we find that forcing the Now Risk agree ment with the number of failures assigned to this mode required removing 98% of the suspensions. This implies only about 2% of the remaining population, a batch, would have a propensity for service conditions to cause a fatigue crack in the transition fillet radius. On a numerical basis, approximately 250 to 260 units of the in service population may have exposure to fatigue crack formation in this transition radius. As the calculations and cumulative graphical plots indicate, the small number s of units in the SB6

- 2 population with exposure to cracking in this transition radius dominate the overall projected risk. The projection indicates about 7 separations due to transition radius cracks will occur in the next year, and nearly half
this small population of about 25 6 units will fail over the next five years. The 0.035/0.0025 transitio n radius is an inherent design defect present in OEM cylinders of the same generation. Population group

Post SB6

- 2 eliminated this deficiency. Most likely

, the projections overstate the risk based on the numbers of OEM cylinders operating, bu t we do not have a sound method to establish a risk reduction
factor. Table 14 presents the results of the risk projection calculations. Figure 12 presents the results graphically.

As with the dome transition radius, we forced the Now Risk computation to have reasonable agreement with the fourteen units assigned to the thread crack CDF. In this case, using 75% of the suspensions forced the Now Risk to agree with the actual recorded separations. The projection indicates seven thread failures in the year and twenty

- tow over the sixty month forecast period. Table 15 presents the risk assessment. Figure 12 presents the results graphically.Report 1102

- 13

Page 32 TABLE 14 . RISK PROJECTION DOME FILL ET RADIUS FAILURES F OR CYLINDER GROUP 6

- 2

TABLE 15 . RISK PROJECTION H EAD THREAD FAILURES FOR CYLINDER GROUP 6

- 2Report 1102

- 13

Page 33 As demonstrated in Figure 12, the projection for failure occurrence in the dome transition radi us dominates the cumulative projected total numbers of failures. Based on the adjusted number of suspension to force Now Risk agreement in group SB6

- 2 we find:

1. A small number of cylinders, about 2% (256 units) that have insufficient margin in the dome

tra nsition radius dominate the cumulative failure projections.

2. Seventy

- five percent of the population has measurable risk for thread failure.

3. Approximately twenty

- three per cent of the population has minimal risk for either failure mode.

Taking all of this in to consideration, we recommend the following continued operational safety actions:

1. Continue the MSB6

- 2 repetitive inspection program.

2. Amend MSB6

- 2 to include visual inspections at fins 9

- 10 and 5

- 7 in addition to fin 17.

3. Amend MSB6

- 2 to require removal of these cylinders at the next engine tear

- down o r published limits for time between overhauls, whichever is first.

4. Ensure MSB6

- 2 includes a clear statement that precludes repair and return of these cylinders to

service.

FIGURE 12 . PROJECTED SEPARAT IONS FOR GROUP SB 6

- 2Report 1102

- 13

Page 34 

### Population Group Post SB6

- 2
With group Post SB6

- 2, AE introduced a new head casting, AEC65385 Rev. D, providing increased wall thickness on the exhaust port side to reduce thermal fatigue cracking in the exhaust port area as identified in MSB6

- 2 . In addition, AE increased the transition fillet radius effectively eliminating the risk of a transition radius failure. Thus, in this population the first loaded thread cracking is the
d ominant failure mode as influenced by operational factors.

Figure 13 shows the Weibull plot derived from Table 5 for reported head

- barrel separations on cylinders with serial numbers associated with Post MSB6

- 2. A Beta close to 1 indicates extensive

ran domization, which suggests mixed failure modes are in operation

, or that operational factors strongly influence the observed performance. In this case, we have identified only one head

- barrel interface separation mode. Therefore, operational factors must have a strong influence on the Weibull
distribution.

FIGURE 13 . GROUP POST MSB6

- 2 DISTRIBUTION OF RE PORTED SEPA RATIONS

Figure 14 presents the cumulative distribution function combining suspensions from Report 1102

- 13 Supplement 3 with the separations listed in Table 5. Suspensions degraded the curve fit as measured by pve, but they tightened the distribution cha racterized by a Beta of 4.838. A large number of low suspensions relative to some of the failures caused this phenomenon. Based on the accepted standard of 100 hour/year in service, the longest in

- service unit has accumulated 518 hours in service as of

1 2/31/2010. Four reported separations had time in service of 835, 1061, 10 85, and 1163 hours,
exceed ing the standard by at least 60% to as much as 220%. As the fleet ages

, the beta value of theReport 1102

- 13

Page 35 distribution will drop and more closely resemble the thread s eparation distributions exhibited by the other population groups.

Without having direct observation identifying one active failure mode, t he point scatter shown in Figure 14 could justify employing a multiple mode data fitting procedure

. In this case, w e have
identified thread failure modes of the outlier points in Figure 14, negating any justification for splitting the data into two separate cumulative distribution functions

. Possible causes of data scatter include:

1. Incorrect reporting of the time in s ervice for separated cylinders

2. Revised cylinder head casting with altered wall configuration

3. Variable and unknown field operating conditions resulting in the head barrel interface temperature exceeding the maximum design temperature limit of 375F

While not likely, the improved cylinder head casting with increased exhaust side wall thickness introduced by AE may have influenced the rate of fatigue crack propagation, thereby altering the distribution shape factor.

The large number of short suspension s , based on an unreliable estimate of time in service

, associated with the eight recorded separations will result in a degraded fit quality found by regression analysis

. The short suspensions allow the higher time failures to bias the distribution as exhibited by the

increase in Beta.

Incorrect time in service reporting would account for some of the data scatter from the best fit curve. Undoubtedly, off

- specification and variable operating conditions

, c ombined with inaccurate cylinder head temperature measurements and improper break

, - in may result in some cylinders operating at
head

- barrel interface temperatures exceeding the maximum temperature design limit resulting in loss
of interference fit

.
Upon examination of Figure 14, we find four relatively short time f ailures and four relatively long

- time failures with no points between the extremes. From additional examination of separated cylinders at AE, we observed evidence of improper break

- in. This condition would allow hot gas to flow by the piston rings and ra is e the interface temperature. Considering the indentified factors, w e can explain
the observed distribution of the separated cylinder data points as follows:

1. The Post MSB6

- 2 cylinder population as designed has insufficient interference fit margin to

comp ensate effectively for non

- optimum field operating conditions.

2. The high time separation points probably represent cylinders operating with excessive cylinder head temperature.

3. The low time separation points probably represent cylinders not receiving a prop er break

- in.

I n the next section , we will estimate the resistance force to remove press fit units at temperature, allowing an assessment of the capability of the cylinder to withstand abnormal operation

.Report 1102

- 13

Page 36 FIGURE 14 . GROUP POST SB 6

- 2 WITH SUSPENSIONS

TABLE 16 . STATISITCAL SUM M ARY OF WEIBULL DATA FOR CYLIDNER GROUP P OST MSB6

- 2

Mode Points Susp. r r 2 ccc 2 pve % η (hrs) β B times (hrs)

1% 2% 5%

1 208 97 208 89 0.93 86 0.8 81 0.8 4 25 20.17 1,1 57 4.8 73 45 0 5 19 6 29

Not surprisingly, the abnormal distribution for cylinder head thread failures lead s to issues with risk projection. Using all the suspensions produced a Now Risk of 93 units failed against 8 reported. This is indicative of a batch problem, attributable to variations in the head

- barrel interference fit. Assuming only 5 % of the suspensions have a propensity for thread failure forced the Now risk to agree with the 8 recorded separations. This result suggests that 9 5 % of the suspended cylind ers have sufficient interference fit to remove at least some load from the threads, which will significant ly improve th read fatigue life allowing the se cylinder s to reach the published overhaul time limit for the engine. Table 17 and Figure 15 present the results of the risk assessment calculation. The risk assessment for group

Post SB6

- 2 projects 8 failures during the next twelve months and 2 6 failures over the next two years.Report 1102

- 13

Page 37 TABLE 17 . RISK PROJECTION H EAD THREAD FAILURES FOR CYLINDER GROUP P OST SB 6

- 2

FIGURE 15 . PROJECTED SEPARAT IONS FOR GROUP POST SB 6

- 2Report 1102

- 13

Page 38 Since this group has the same interface design as g roup SB 6

- 2, we would expect thread failures to

occu r. The tighter clustering of the Weibull distribution curve with a characteristic life of 1,1 57 hours
prompts a very conservative approach on how to treat this population group

. The best approach would be to find and remove cylinders that may have less t han sufficient interference fit , but complete production records are not available for these units. We base the following recommendations on
MSB6

- 2 and the foregoing statistical analysis :

1. Issue a mandatory service bulletin call ing for repetitive inspections of cylinders beginning at 250
hours.

2. Focus the inspection for cracks at fin 5

- 7 as well as fin 17.
3. Require r etire ment all cylinders in this population group at the engine mandatory overhaul
limit.

4. Require mandatory checks for oil consumption and examination of cylinders if oil consumption exceeds a predetermined limit.

5. Require removal of cylinders consuming excessive oil for rehoning, reinstallation, and break

- in to prevent excessive cylinder interface temperature.



### Repaired C ylinder Assemblies
Cylinders identified as repaired unit s in Table 7 that experienced a stripped thread separation. Figure 16 provides a preliminary Weibull curve for this failure mode in the interest of establishing a baseline for further investigation. The distribution presented in Figure 16 is characteristic of a typical fatigue
wear out failure. Lack of available data precludes any further analysis at this time.

AE issued repair station instructions in 2009 requiring repaired and reassembled cylinder s to have
head

- - barrel interference fits set at current standards

. As part of an overall COS program, we recommend establishing a serial number tracking system for repaired units. This would allow better
assessment of in

- service performance and identif y necessary improve activities as needed for the repaired products.Report 1102

- 13

Page 39 FIGURE 16 . PRELIMINARY DSITR UTION FOR REPAIRED C YLINDERS WITH STRIPP ED THREADS



## Analysis of Head

- Barrel Interface

Population Group Identification and Material Properties
For the purposes of assessing the effectiveness of the head

- barrel interference fit, two groups governed by the revision level of AEC631399 represent the entire cylinder population:

1. Group H

- J

- K

- L including Groups 4

- 1, 6

- 2, and Post 6

- 2

2. Group N representing Group Post 6

- 2

- INT

- A

Table 18 recasts Table 1D for base line fit dimensions at the interface.

TABLE 18 . BASELINE HEAD

- BARREL INTERFACE DIA METERS FROM AEC63139 9

Group Date

Start Date End J

- Head Pitch

Max . Dia. (in) J

- Head Pitch

Min . Dia. (in) H

- Head

Band Max

. Dia. (in) H

- Head

Band Min

. Dia. (in)

H

- J

- K

- L 8/29/02 10/12/09 5.554 5.552 5.459 5.457

N 10/13/09 Current 5.552 5.550 5.453 5.451

Calculation of interference fit and removal force require additional data. Table 19 lists dimensional data taken from published drawings or the type certificate 6 and Table 20 lists physical and mechanicalReport 1102

- 13

Page 40 property data for the materials of construction taken from published literature for Aluminum 242.0 7

, for Piston Alumin um Alloy A4032 8 and for SAE4140 steel 9

. The characteristics listed in Table 19 are common to all drawing revisions covering the production run. For convenience, we referred to the
latest revision level.

TABLE 19 . SUPPLEMENTAL DI MENSION DATA REQUIRE D FOR FORCE CALCULAT IONS

Location Characteristic Drawing Rev. Nominal (in)

Head Outside Diameter AEC65385 J 6.750

Head Thread Length AEC631399 N 0.6875

Head Estimated Shrink Band Engaged Length AEC631399 N 0.336

Barrel Inside Diameter AE65041 K 5.252

Barrel Thread Length AEC634501 V 0.6875

Barrel Estimated Shrink Band Engaged Length AEC634501 V 0.3360

Piston Diameter (From type certificate data) FAA E8CE 21 5.250

TABLE 20 . PHYSICAL AND MECA HNICAL PROPERTIES OF CYLIND ER HEAD AND BARREL M ATERIALS

A242 Material Properties T77 Temperature (F)

68 212 375 400 425 600 Ultimate Strength (psi) 30,000 30,000 21,500 20,000 18,700 8,000
Yield Strength (psi) 23,000 23,000 16,000 15,000 13,800 4,000
%El 2 2 3 20 Modulus (psi) 1.03E+07 1.03E+07 1.03E+07 1.03E+07 1.03E+07
Poison Ratio 0.33 0.33 0.33 0.33 0.33 Expansion Coefficient 1.360E

- 05 1.360E

- 05 1.360E

- 05 1.360E

- 05 A242 Head Geometry Temperature (F)

68 300 375 400 425
Head Outside Diameter (inch) 6.7500 6.7713 6.7782 6.7805 6.7828 Nominal Thread Length (inch) 0.7500 0.7531 0.7534 0.7536 Temperature (F) AISI 4140 Material Properties

- Austenize + Oil Quench + Temper 68 212 375 400 425

Ultimate Strength (psi) 158700 158700 158700 158700 158700
Yield Strength (psi) 142300 142300 142300 142300 142300
%El 14.8 14.8 14.8 14.8 14.8
%RA 48.9 48.9 48.9 48.9 48.9
Modulus (psi) 2.90E+07 2.90E+07 2.90E+07 2.90E+07 2.90E+07
Poison Ratio 0.3 0.3 0.3 0.3 0.3 Expansion Coefficient 7.120E

- 06 7.120E

- 06 7.170E

- 06 7.170E

- 06Report 1102

- 13

Page 41 AISI 4140 Barrel Geometry Temperature (F)

68 300 375 400 425
Barrel Inside Diameter (inch) 5.2520 5.2574 5.2635 5.2645 5.2654 Nominal Thread Length (inch) 0.7500 0.7508 0.7516 0.7518 0.7519

Est. Shrink Band Length (inch) 0.34800 0.34836 0.34876 0.34883 0.34889
Data to Calculate Combustion Force Alloy 4032 Temperature (F)

68 300 375 400 425
Piston Diameter 5.2500 5.2643 5.2689 5.2704 5.2719 Piston Alloy 4032 Exp. Coeff. 1.17E

- 05 1.17E

- 05 1.17E

- 05 1.17E

- 05 Peak Pressure (AEC data) psi 900 900 900 900 900

Force on P iston (lb) 19,483 19,589 19,623 19,634 19,646



### Notes to Table 19:

1. T77 Heat treatment: Solutionize at 960F

- 4Hr

- Still Air Quench, age at 650F

- 2Hr
2. Aluminum ultimate and yield strength at 375F was extrapolated from a graph constructed from the published data 212F, 400 , and 600. See Attachment 2

. 3. A242 coefficient of thermal expansion is valid to 512F

4. SAE 4140 Steel Heat Treatment: Normalize at 1625F

- 3Hr air cool, austenize at 1600F

- 1/2Hr oil quench, temper at 1100F

- 2Hr air cool

5. Thermal expansion coefficient s for steel from 68F to 400F and 425 F w ere extrapolated from a plot of maximum temperature vs. expansion coefficient. See Attachment 3.



### Coefficient of Slidi ng Friction
For cylinders, Equation 4 shows p ress fit removal force directly related to coefficient of friction, contact pressure, and the contact area :

EQUATION 4

.

Where:

F = Removal force

μ = coefficient of sliding friction

σ = Radial contact pressure

r = Common radius between inner and outer sleeves L = Length of contact area

Knowing the geometry, measured removal force, and contact pressure allows for direct computation
of the coefficient of friction. AE conducted push

- off tests and reported the results in terms of measured pressure and diametrical interference fit on AEC631397 cylinder geometry set at nominal
and maximum interference 10 . Using Equation 4 and the supplied data, the author c omputed the
friction coefficient.Report 1102

- 13

Page 42 Attachment 4 presents the raw data and details of the calculations giving an effective coefficient of friction at two interference fit levels. Figure 17 presents the computations from Attachment 4 as a plot
of the coeff icient of friction as a function of radial interference. Removal force calculations discussed later would incorporate the empirical relationship of coefficient of friction with radial interference shown on the plot

.

FIGURE 17 . R ELATIONSHIP OF COEFF ICIENT OF FRICTION T O RADIAL INTERFERENC E



### Interference Fit Estimates at Operating Temperature
Using data from Tables 18, 19 and 20, we calculated expanded thread pitch and shrink band diameters
and the related interference fits from 350F through 425F at 25F intervals using Equation 4 for the following assembly interference fit conditions:

1. Nominal

2. Condition 1

- Maximum interference at the shrink band and the threads
3. Condition 2

- Minimum interference at the shrink band and the th reads

4. Condition 3

- Maximum interference in the threads, minimum interference in the shrink band

5. Condition 4

- Minimum interference in the threads, maximum interference in the shrink band 

### y = 224.68x + 0.2311

0 1 2 3 4

0.0000 0.0020 0.0040 0.0060 0.0080 0.0100 0.0120 Coefficient of Friction



### Radial Interference (in)



## Estimated Friction CoefficientReport 1102

- 13

Page 43 EQUATION 5

.

Where:

D f = Diameter at temperature

D i = Diameter at 68F

α = Mean coefficient of thermal expansion between 68F and the operating temperature

T f = Operating temperature (F)

Attachment 5 presents the tabulated results of these computations for each indentifi ed cylinder interface configuration . Figures 1 8 through 2 2 show the graphical relationship of diametrical interference for each condition at each selected cylinder thread operating temperature including:

1. 350F, an operating condition 25F below design maximum thread temperature

2. 375F, design maximum thread temperature

3. 400F, an operating condition 25F above design maximum thread temperature

4. 425F, an operating condition 50F above design maximum thread temperature

Study of Figures 1 8 through 2 2 leads to a n umber of observations for the various assembled
interference fit conditions:

1. At nominal interference fit group H

- J

- K

- L, which includes all cylinder assemblies with reported head barrel separations, loses positive head

- barrel interference fit at about 385 F or just above design point maximum operating temperature of the interface.

2. At nominal interference fit

, group N retains positive interference fit through 425F.

3. At Condition 1 interference fit, group H

- J

- K

- L retains positive interference fit to 425F.

4. At C ondition 1 interference fit, group N retains positive interference fit through 425F.

5. At Condition 2, minimum interference fit, group H

- J

- K

- L loses positive interference fit at 325F.

6. At Condition 2, group N thread pitch diameter loses positive interference fit at 375F while the shrink band retains positive interference fit through 425F.

7. At Condition 3, maximum thread interference with minimum band interference, group H

- J

- K

- L retains positive interference fit of the thread pitch diameter to 425F, but the shri nk band loses positive interference fit at 325F.

8. At Condition 3, group N retains positive interference fit through 425F.

9. At condition 4, minimum thread interference with maximum band interference, group H

- J

- K

- L retains a positive shrink band interference f it through 425F, but the thread pitch diameter loses positive interference fit at 325F.

10. At Condition 4, g roup N retains a positive shrink band interference fit through 425F, but the thread pitch diameter loses positive interference fit at 375F.

F or g roup H

- J

- K

- L
, cylinders with Nominal or Condition 1 interference fits will withstand engine operating condition s better than cylinders assembled to the Condition 2, minimum, interference fit. At
fit Condition 2, the threads will carry the combustion pulse load at head

- barrel interfaceReport 1102

- 13

Page 44 temperatures above 325F. In fit Conditions 3 and 4 the thread pitch diameter or shrink band diameter retain a positive interference fit to about 425F. Interference fit removal force estimates will shed more light on the relati ve contributions of the shrink band and thread length to the overall load carry capacity of the assembly

, as well as providing more quantitative guidelines for targeting cylinders at greater risk of experiencing a head

- barrel separation.

Similarly, we fi nd g roup N retains positive interference fit through 425F at both the thread pitch diameter and the shrink band diameter for Nominal, Condition 1, or C ondition 3 interference fit. The thread pitch diameter loses positive interference fit at 375F for Condi tion 2 and Condition 4. This suggests the thread pitch diameter requires increase interference at assembly. Interference fit removal force calculations will provide quantitative guidelines for optimizing the interference fit settings of g roup N, current production cylinders.

FIGURE 18 . NOMINAL

- DIA. INTERFERENCE FI T AT INTEFACE OPERAT ING TEMPERATURES



### - 0.0040 - 0.0020 0.0000 0.0020 0.0040 0.0060 0.0080 0.0100 0.0120 0.0140 0.0160 0.0180 0.0200

0 50 100 150 200 250 300 350 400 450 Interference (in.)



## Interface Temperature (F)

Condition

- Nominal Interference Fit

HKL Shrink Band HKL Threads N Shrink Band N ThreadsReport 1102

- 13

Page 45 FIGURE 19 . CONDITION 1

- DIA. INTERFERENCE FI T AT INTEFACE OPERAT ING TEMPERATURES



### 0.0000 0.0020 0.0040 0.0060 0.0080 0.0100 0.0120 0.0140 0.0160 0.0180 0.0200 0.0220

0 50 100 150 200 250 300 350 400 450 Interference (in.)



## Interface Temperature (F) Condition 1

- Maximum Interference Fit

HKL Shrink Band HKL Threads N Shrink Band N ThreadsReport 1102

- 13

Page 46 FIGURE 20 . CONDITION 2

- DIA. INTERFERENCE FI T AT INTEFACE OPERAT ING TEMPERATURES



### - 0.0060 - 0.0040 - 0.0020 

### 0.0000 0.0020 0.0040 0.0060 0.0080 0.0100 0.0120 0.0140 0.0160

0 50 100 150 200 250 300 350 400 450 Interference (in.)



## Interface Temperature (F) Condition 2

- Minimum Interference Fit

HKL Shrink Band HKL Threads N Shrink Band N ThreadsReport 1102

- 13

Page 47 FIGURE 21 . CONDITION 3

- DIA. INTERFERENCE FI T AT INTEFACE OPERAT ING TEMPERATURES



### - 0.0060 - 0.0040 - 0.0020 0.0000 0.0020 0.0040 0.0060 0.0080 0.0100 0.0120 0.0140 0.0160 0.0180

0 50 100 150 200 250 300 350 400 450 Interference (in.)



## Interface Temperature (F) 

# Condition 3

- Max. Thread, Min. Band

Interference

HKL Shrink Band HKL Threads N Shrink Band N ThreadsReport 1102

- 13

Page 48 FIGURE 22 . CO NDITION 4

- DIA. INTERFERENCE FI T AT INTEFACE OPERAT ING TEMPERATURES



### Removal Force Estimates
Using the at

- temperature computed diameters and parameters listed in Tables 18 through 20 and the empirical formula for friction coefficient shown in Figure 17

, we applied standard formulations provided by Excelcalcs.com (ref. 3) to compute estimated press fit removal force contributions from the shrink band and thread pitch line for each nominal, maximum (C1), and minimum (C2) interface fit
condition s

. Additiona lly , we computed wall contact stress at the interface for each condition. The preceding review of the current production cylinder population

, identified for this analysis as g roup N
, suggested that current interference fit par ameters would result in the thread pitch line losing positive interference at the maximum design operating temperature. This prompted an evaluation of a potential modification of g roup N by increasing interference fit by 0.004

- inch and by 0.009

- inch from the current settings. We begin by considering the interface condition identified by HKL, which represents cylinders produced through 10/12/2009 and includes identified populations SB4

- 1, SB6

- 2
and Post SB6

- 2. 

### - 0.0060 - 0.0040 - 0.0020 0.0000 

### 0.0020 0.0040 0.0060 0.0080 0.0100 0.0120 0.0140 0.0160 0.0180 0.0200 0.0220

0 50 100 150 200 250 300 350 400 450 Interference (in.)



## Interface Temperature (F) 

# Condition 4

- Min. Thread, Max. Band

Interference

HKL Shrink Band HKL Threads N Shrink Band N ThreadsReport 1102

- 13

Page 49 GROUP HKL
Table 21 relates the computed room t emperature diametrical interference of the thread pitch and
shrink band diameter to each fit condition . Tables 22 and 23 summarize results of removal force computations for the thread and shrink band sections of the interface , computed at 68F, 300F, 375F
and 400F (Attachment 5)

. Refer to Report 1102

- 13 Supplement 5 for details of these computations.

TABLE 21 . SUMMARY OF INTEFE RENCE SETTINGS FOR G ROUP HKL

Fit Condition Description Shrink Band Interference (in.) Thread Pitch Diameter Interference (in.)

Nominal Nominal interference settings 0.0115 0.0115

1 Maximum interference 0.014 0.014

2 Minimum Interference 0.009 0.009

3 Minimum band, maximum thread

interference 0.009 0.014

4 Maximum band, minimum thread

interference 0.014 0.009

TABLE 22 . GROUP HKL REMOVAL FORCE ESTIMATES FOR PRESS FIT CONDITIONS

Interface Temperature (F) Force S hrink Band (lb) Force Threads (lb) Total F orce (lb)
Nominal

68 14
, 287 34,881 49,168

300 1
, 649 3,920 5,569

375 177 299 476

400
Condition 1 (maximum)

68 20,679 50,387 71,066

300 4,251 10,362 14,613

375 1,394 3,556 4,950

400 751 1,921 2,672
Condition 2 (minimum)

68 9,084 22,223 31,307

300 217 421 638

375 0 0

400 0 0
Condition 3

68 9,084 50,387 59,471

300 217 10,579Report 1102

- 13

Page 50 Interface Temperature (F) Force S hrink Band (lb) Force Threads (lb) Total F orce (lb)

375 0 3,556 3,556

400 0 1,921 1,921
Condition 4

68 20,679 22,223 42,902

3 00 4,251 421 4,672

375 1,394 0 1,394

400 751 0 751

Table 23 present s a consolidated summary of total removal force for press fit cylinder head

- barrel assemblies at various temperatures.

TABLE 23 . SUMMARY OF TOTAL PRESS FIT REMOVAL FO RCES FOR CYLINDER GROUP HKL

Interface Temperature (F) Total Estimated Removal Force (lb)

Nominal Condition 1

(maximum) Condition 2

(minimum) Condition 3 Condition 4

68 49,168 71,066 31,307 59,471 42,902

300 5,569 14,613 638 10,579 4,672

375 476 4,950 0 3,556 1,394

400 0 2,672 0 1,921 751

Using the 900 psi maximum peak pressure measured by AE 11 for the TCM 520/550 series engines and allowing for piston expansion, we computed estimated peak pressure load pulses for these cylinder
assemblies in Table 20

. The head

- barrel assembly must resist this computed peak load. If the total estimated press fit removal force does not match or exceed the peak cyclic force, then the threads will have to absorb the portion of the load not withsto o d by the interference fit. As more load transfers
into the thread s, the fatigue characteristics of aluminum 242 alloy at the interface temperature determines the operational life of the cylinder assembly . Experience has shown that cyclic loads in the threads cause failure in between 500 and 1,000 hours in service or ap proximately 8 x 10 6 to 3.2 x 10 7 fatigue cycles based on an engine operating at 2700 rpm and pro du cing peak power for 10% of the
total operating time. The cyclic stress

- cycles to failure relationship is quite flat in this region of the fatigue curve , im plying that small changes in cyclic load will have a significant impact on extending the longevity of cylinders 12

. Figure 23 graphically presents the results of these calculations. The shaded area in the figure represents the region in which threads to be gin absor bing cyclic loads. Attachment 6 contains graphical presentations of the individual components for the nominal, maximum , and
minimum interference fit conditions

.Report 1102

- 13

Page 51 FIGURE 23 . TOTAL REMOVAL FOR CE FOR GROUP HKL

At 900 psi peak combustion pressure, o ur removal force estimates suggest that cylinders assembled at
the minimum interference limit will begin transferring load to the threads at about 250F with the threads absorbing all the combustion force at 325F. Cylinders prod uced with the nominal interference fit will carry about 28% of the combustion force load at 300F and 10% of the combustion force load at

350F

. Similarly

, cylinders produced with maximum in t erference fit will carry about 75% of the
combustion force load at 300F and 25 % of the combustion force load at 375F. These interference fit load bearing estimates suggest actual operating interface temperatures and/or peak combustion

pressure for the majority of the cylinders must be below 375F because of the relativel y few reported separations.

Based on the Weibull plots with the implication of lower than estimated maximum interface
temperature and peak combustion pressure

, cylinders assembled with nominal or greater interference will perform in the field to the sched uled overhaul limit. For g roup SB6

- 2 , we have shown the major risk appears due to cylinders machined at the minimum limit of the shr ink band to dome transition radius, which is not related to the thread fatigue failure. Meanwhile, the removal force estim ates



### 0 10,000 20,000 30,000 

### 40,000 50,000 60,000 70,000

50 100 150 200 250 300 350 400 450 Total Removal Force (lb)



## Interface Temperature (F) HJKL Temperature

- Force Relationship

Nom. Total C1 Total C2 Total C3 Total C4 TotalReport 1102

- 13

Page 52 suggest that any cylinder assembled with near minimum interference fit will carry a higher risk of thread fatigue failure, yet the Weibull risk assessment suggests only a small fraction of this population is prone to the thread fatigue failure. There fore, we believe our previously stated recommendations to remove these cyli n ders from service at the next engine teardown require no modifications

.

As with the MSB6

- 2 population, t he Post SB6

- 2 population has risk of thread fatigue failure, which is

entire ly understandable based on removal force calculations. As previously stated, we recommend issuing a mandatory service bulletin requiring a number of actions:

1. Require repetitive inspections each 50

- hours for Post MSB6

- 2 cylinders beginning at 250 hours.

2. Fo cus the inspection for cracks at fin 5

- 7 as well as fin 17.
3. Require retirement all cylinders in this population group at the engine mandatory overhaul
limit.

4. Require mandatory checks for oil consumption and examination of cylinders if oil consumption

exc eeds a predetermined limit.

5. Require removal of cylinders consuming excessive oil for rehoning, reinstallation, and break

- in to prevent excessive cylinder interface temperature.

6. If records are available, we recommend identifying cylinders produced at the minimum interference fit and require their removal within the next 200

- hours.

GROUP N Report 11

- 02

- 13 Supplement 5 contains the detailed estimates of removal force for the nominal, maximum, and minimum interference fit conditions incorporating expanded thread pitch and shrink
ba n d diameters previously calculated as well as information presented in Tables 19 and 20. Tables 2 4
, 2 5 , and 2 6 present the removal force estimate and summary for g roup N, which represents the current production group identified as Post SB6

- 2

- INT

- A. Attachment 6 presents a graphical summary of the thread and shrink band contribution to removal force for the nominal, maximum, and minimum press
fit conditions.

The int e r face load carrying capacity of the current production units represent a significant improvement over the cylinder assemblies produced through October 2009. As illustrated in Figure 24, press fit conditions nominal, maximum, C3, and C4 will carry at leas t 50% of the combustion load through 375F. The minimum fit condition will carry 20% of the combustion force load at 350F and 10%
of the load at 375F. B ased on the statistical behavior shown in the HKL population group as well as
inference of lower than a nticipated head

- barrel interface temperature and peak combustion pressure

, we believe there is no immediate cause for concern.

Clearly, operating conditions, break

- in procedures, and cooling baffle configuration have a direct bearing on the service life of any cylinder because they influence the actual cylinder head

- barrel interface temperature. Lower interface temperatures will result in greater cylinder longevity with reduced risk of thread fatigue. Taken together, the statistical data, uncertainty of actual operating
conditions at the head

- barrel interface, the ambiguity of peak combustion pressure, and the push

- off resistance force calculations showing load transfer to the threads at interface temperatures well belowReport 1102

- 13

Page 53 design maximum strongly sugge st AE should conduct tests to directly measure the head

- barrel interface temperature and peak combustion pressure.

The press fit removal force estimates for current production cylinders produced at or above nominal
interference indicate these units will perform up to the maximu m design temperature of 375F. W ith respect to current production cylinders produced at minimum interference and considering the influence of operating conditions we recommend the following actions:

1. Review production records and ide ntify any current production cylinders produced with
minimum interference

. 2. Conduct tests to directly measure head

- barrel interface temperature and peak combustion

pressure of an operating TSIO

- 520NB at these suggested conditions:

a. Maximum manifold pressur e, rated maximum cylinder head temperature
b. Maximum manifold pressure, rated maximum cylinder head temperature plus 25F

c. Maximum manifold pressure, rated maximum cylinder head temperature plus 50 F
3. If head

- barrel interface temperature exceeds 300F at maximu m head temperature, c onsider issuing a service bulletin call for removal of cylinders produced at minimum interference after
84 months or 700

- hours in service , replacing them with cylinders having greater assembly
interference

. 4. Consider issuing a service g uideline bulletin to all ECi customers explaining the necessity for:

a. proper break

- in of cylinders
b. inspection for and removal of cylinders incorrectly broken in

c. Inspection and restoration of all cooling baffles and devices to their properly certified configuration to minimize heat stress on the cylinder joints

5. Adjust assembly interference fit requirements to avoid thread load transfer up at head

- barrel
interfac e temperature corresponding to rated maximum head temperature plus 50F

6. A s a precaution, AE should produce current production cylinders with interference fit levels set
at nominal or above.

7. Pending definitive determination of the head

- barrel interface tem perature corresponding to head temperatures 50F above maximum limit, AE should consider adjusting assembly
interference fit to avoid load transfer to the thread s up to 425F head

- barrel interface
temperature.

TABLE 24 . SUMMARY OF INTEFERENCE SETTINGS FOR GROUP N

Fit Condition Description Shrink Band Interference (in.) Thread Pitch Diameter Interference (in.)
Nominal Nominal interference settings 0.0175 0.0135

1 Maximum interference 0.020 0.016

2 Minimum Interference 0.015 0.011

3 Minimum band, maximum thread

interference 0.015 0.016

4 Maximum band, minimum thread 0.02 0.011Report 1102

- 13

Page 54 interference

TABLE 25 . GROUP N REMOVAL FORCE ESTIMA TES FOR PRESS FIT CO NDITIONS

Interface Temperature (F) Force Shrink Band (lb) Force

Threads (lb) Total Force (lb)

Nominal

68 8,407 15,804 24,211

375 3,208 2,913 6,121

400 2,802 1,882 4,684 Condition 1 (maximum)

68 9,645 18,765 28,410

375 4,842 5,835 10,677

400 4,025 4,832 8,857 Condition 2 (minimum)

68 7,179 12,853 20,032

375 2,003 0 2,003

400 1,588 0 1,588
Condition 3

68 7,179 18,765 25,944

375 2,003 5,835 7,838

400 1,588 4,832 6,420
Condition 4

68 9,645 12,853 22,498

375 4,421 0 4,421

400 4,025 0 4,025

TABLE 26

. SUMMARY OF TOTAL REM OVAL FORCES OF CYLIN DER GROUP N

Interface Temperature (F) Total Estimated Removal Force (lb)

Nominal Condition 1

(maximum) Condition 2

(minimum) Condition 3 Condition 4

68 24,211 28,411 20,032 25,944 22,498

375 6,121 10,256 2,003 7,838 4,421

400 4,684 8,857 1,588 6,420 4,025Report 1102

- 13

Page 55 FIGURE 24 . TOTAL REMOVAL FOR CE FOR GROUP N

GROUP N MODIFI CATIONS As a means of improving robustness of the cylinder interface, we next examine cylinders modified to
increase interference by 0.004

- inch, identified as N+004, and by 0.009

- inch, identified as N+009. From the resistance force estimates on these cylinders, we can construct an engineering curve to better
estimate the minimum increase in interference fit that will re sult in no load transfer to the threads at interface temperatures between 375F and 425F.

Table 27 provides the interference settings for both configuration s

. Report 11

- 0 2

- 13 Supplement 5 contains the detailed estimates of removal force for the nominal, maximum, and minimum interference fit conditions incorporating expanded thread pitch and shrink bad diameters previously calculated as well as information presented in Tables 19 and 20. Tab les 28 and 29 present results of
the removal force estimates for each condition. Table 3 0 summarizes the contact pressure estimates. Attachment 6 presents a graphical summary of the thread and shrink band contribution to removal force for the nominal, ma ximum, and minimum press fit conditions. Figure s 2 5 and 26 graphically
summarize these results . Modification N+004 at minimum fit condition will begin transferring



### 0 10,000 20,000 30,000 

### 40,000 50,000 60,000 70,000 80,000 90,000 100,000 

### 110,000

50 100 150 200 250 300 350 400 450 Removal Force (lb)



## Interface Temperature (F) 

# N Temperature

- Force Relationship

Nom. Total C1 Total C2 Total C3 Total C4 TotalReport 1102

- 13

Page 56 combustion load into the threads at 350F. Modification N+009 will not transfer load using any fit
condition through 425F interface temperature

.
Using minimum fit condition total resistance force for conditions N, N+004, and N+009 from Tables 26
and 28 we constructed Figure 27 to permit estimation of the adjustment necessary to avoid transfer of
load to the threads for various head

- barrel interface temperatures. Our estimates show that adjusting interference fit by 0.007

- inch will avoid combustion load transfer to the threads up to a head

- barrel interface temperature of 425F. Table 30 sho ws modification N+009 will result in contact pressures approximately 1 4 % of the published yield strength of the aluminum head alloy. Taking safety, operational, and mechanical factors into consideration, w e recommend AE consider implementing an adjustment to increase assembly interference fit by 0.007

- inch.

TABLE 27 . INTEFERENCE SETTI NGS FOR GROUP N +004 AND N+009

Fit Condition Description Shrink Band Interference (in.) Thread Pitch Diameter Interference (in.)

N+004
Nominal Nominal interference settings 0.0215 0.0175

1 Maximum interference 0.024 0.020

2 Minimum Interference 0.019 0.015
3 Minimum band, maximum thread

interference 0.019 0.020

4 Maximum band, minimum thread

interference 0.024 0.015

N+009
Nominal Nominal interference settings 0.02 6 5 0.0 22 2 5

1 Maximum interference 0.02 9 0.02 5

2 Minimum Interference 0.0 24 0.0 20

3 Minimum band, maximum thread

interference 0.0 24 0.0 25

4 Maximum band, minimum thread

interference 0.02 9 0.0 20

TABLE 28

. GROUP S N +004 AND N+009 REMOVAL FORCE ESTIMA TES

Interface Temperature (F) Force Shrink Band (lb) Force Threads (lb) Total Force (lb)

N+004 Nominal

68 46,838 81,202 128,040

375 12,275 12,664 24,939

400 10,707 10,451 21,158

425 9,553 7,785 17,338

N+004 Condition 1 (maximum)

68 57,526 103,719 161,245Report 1102

- 13

Page 57 Interface Temperature (F) Force Shrink Band (lb) Force Threads (lb) Total Force (lb)

375 18,501 23,329 41,830

400 16,586 19,917 36,503

425 14,666 15,649 30,315

N+004 Condition 2 (minimum)

68 35,262 59,933 26,620

375 7,668 5,754 8,609

400 6,423 3,850 7,248

425 5,249 2,366 6,191

N+004 Condition 3

68 35,262 59,933 138,981

375 7,668 5,754 30,997

400 6,423 3,850 26,340

425 5,249 2,366 20,898

N+004 Condition 4

68 57,526 59,933 117,459

375 18,501 5,754 24,255

400 16,586 3,850 20,436

425 14,666 2,366 17,032

N+009 Nominal

68 69,871 129,670 199,541

375 25,630 36,596 62,226

400 23,105 31,933 55,038

425 20,959 27,688 48,647

N+009 Condition 1 (maximum)

68 82,849 159,037 241,886

375 34,151 53,124 87,275

400 31,043 47,557 78,600

425 28,606 41,182 69,788

N+009 Condition 2 (minimum)

68 55,118 103,336 158,454

375 18,464 23,526 41,990

400 16,307 19,756 36,063

425 14,461 16,283 30,744

N+009 Condition 3

68 55,118 159,037 214,155

375 18,464 53,124 71,588

400 16,307 47,557 63,864

425 14,461 41,182 55,643

N+009 Condition 4

68 82,849 103,336 186,185

375 34,151 23,526 57,677Report 1102

- 13

Page 58 Interface Temperature (F) Force Shrink Band (lb) Force Threads (lb) Total Force (lb)

400 31,043 19,756 50,799

425 28,606 16,283 44,889

TABLE 29 . SUMMARY OF TOTAL REMOVAL FORCES FOR CYLINDER GROUP S N +004 AND N+009

Interface Temperature (F) Total Estimated Removal Force (lb)

Nominal Condition 1

(maximum) Condition 2

(minimum) Condition 3 Condition 4

N+004

68 128,040 161,245 95,195 138,981 117,459

375 24,939 41,830 13,422 30,997 24,255

400 21,158 36,503 10,273 26,340 20,436

425 17,338 30,315 7,615 20,898 17,032

N+009

68 199,541 241,886 158,454 214,155 186,185

375 62,226 87,275 41,990 71,588 57,677

400 55,038 78,600 36,063 63,864 50,799

425 48,647 69,788 30,744 55,643 44,889

TABLE 30 . CONTACT PRESSURE FOR N +004 AND N+009 AT MAXIMUM INTEFEREN CE FIT

Temperature (F) Shrink Band (psi) Thread Pitch Diameter (psi)

N+004

68F 3,286 3,192

375 1,797 1,426

400 1,699 1,312

425 1,590 1,143

N+009

68F 3,970 3,990

375 2,488 2,228

400 2,373 2,108

425 2,273 1,941Report 1102

- 13

Page 59 FIGURE 25 . TOTAL REMOVAL FOR CE FOR GROUP N +004



### 0 20,000 40,000 

### 60,000 80,000 100,000 120,000 140,000 160,000

50 100 150 200 250 300 350 400 450 Removal Force (lb)



## Interface Temperature (F) 

## N+004 Temperature Force Relationship

Nom. Total C1 Total C2 Total C3 Total C4 TotalReport 1102

- 13

Page 60 FIGURE 26 . TOTAL REMOVAL FOR CE FOR GROUP N+009



### 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000 

### 180,000 200,000 220,000 240,000 260,000

50 100 150 200 250 300 350 400 450 Removal Force (lb)



## Interface Temperature (F) 

## N+009 Temperature

- Force Relationship

Nom. Total C1 Total C2 Total C3 Total C4 TotalReport 1102

- 13

Page 61 FIGURE 27 . EFFECT OF IN TERFERENCE CHANGES ON TOTAL REMOVAL FOR CE FOR GROUP N



### 0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 45,000

- 0.002 0.000 0.002 0.004 0.006 0.008 0.010 Total Removal Force (lb)



## Assembly Interference Changes, Diametrical (in.) 

## Rev. N Modifications: Force

- Interference Change

375F

- Min. 400F

- Min. 425F

- min.

MINIMUM INTERFERNCE FIT

0.000 = Baseline AEC631399 Rev. NReport 1102

- 13

Page 62 

## FINDINGS AND RECOMMENDATIONS

Findings

1. The production run of AEC631397 replacement cylinders for TCM 520/550 series engines fall into population groups defined by two critical service bulletins:

a. Group SB4

- 1
b. Group SB6

- 2

c. Group Post SB6

- 2
d. Group Post SB6

- 2 with improved interference and intake valve seats with an Allison style back

2. AE has not implemented sequential serialization of cylinder shipments requiring use of both shipping dates and serial numbers to determine population groups. This introduces some

unc ertainty in determining configuration of cylinders in service, resulting in less than desirable precision in identifying cylinders subject to specific service bulletins.

3. Based on production and warranty return information

, w e established total production a nd recorded failures for each identified population group as follows:

a. Group SB4

- 1: 2,572 total, 4 recorded failures plus 31 failures reported to FAA
b. Group SB6

- 2: 13,615 total, 21 failures, 756 warranty removals

c. Group Post SB6

- 2: 20,937 total, 8 failures, 4 0 warranty removals
d. Group Post SB6

- 2

- INT

- A: 6,643 total, no failures

4. Service Bulletin MSB4

- 1 ma n dated inspection for cracks at fin 9

- 10 counting from the bottom and inspection by AE for proper heat treatment

5. Service Bulletin MSB6

- 2 mandated repetitive inspection for cracks each 50

- hours at fin 17 on
the exhaust side.
6. Introducing head casting AEC65385 Rev. D minimized exhaust port side cracks.

7. Critical features of barrel design AEC634501 affecting interference fit did not change significantly over the pr oduction run.
8. Critic al choke and barrel inside diameter dimensions defined by AE65041 did not change over the production run.

9. AEC631399 Rev. H set the s hrink band to dome transition fillet radius at 0.035/0.025

- inch

, which applied to cylinder groups SB4

- 1, SB6

- 2, and Post SB6

- 2.
10. Beginning with g roup Post SB6

- 2, AEC631399 Rev. J set the shrink band to dome transition radius at 0.050/0.040

- inch

. 11. Cylinder g roups SB4

- 1, SB6

- 2, and Post SB6

- 2 were produce d with diametrical interference fits defined by AEC631239 9 Rev. H through L at 0.014/0.009

- inch.

12. Cylinders produced from October 13, 2009 incorporated an increased diametrical interference
fit of 0.020

- inch nominal at the shrink band and 0.015

- inch nominal in the threads

. 13. Visual examination confirmed three fail ure modes:

a. Transition shrink band to dome fillet radius fatigue cracking
b. Fatigue cracking of the first loaded head thread

c. Thread stripping of repaired cylinder assembliesReport 1102

- 13

Page 63 14. We found no effective correlation between reported time in service and computed stand ard time in service for this population group.

15. Lack of correlation between actual and standard time in service will introduce statistical error in Weibull plots
16. Statistical analysis determined three failure modes within g roup SB4

- 1:

a. Shrink band to dome transition fillet radius failure on improperly heat treated cylinders
b. Shrink band to dome transition fillet radius failure on correctly heat treated cylinders

c. First load thread fatigue crack failures on correctly heat treated cylinders

17. Statistical analysis of g roup MSB4

- 1 strongly suggested fillet radius failure of the population remaining in service is unlikely.

18. Statistical analysis of Group MSB4

- 1 projected 10 addit i onal failures over the next five years.
19. Consolidated Weibull plot of Group MSB6

- 2 showed c lear evidence of multiple failure modes, which were confirmed by visual examination of units in storage at AE.

20. Risk projection calculations for Group MSB6

- 2 suggest only 250 to 260 cylinders remain at risk of fatigue cracking in the head shrink band to dom e transition fillet radius.

21. Projected risk for MSB6

- 2 indicates 19 failures will occur in the head fillet radius over the next
24 months for this population group. In the same period, only 8 failures are projected in the
first loaded head thread.

22. Populat ion G roup Post MSB6

- 2 has not exhibited transition radius fatigue cracks.
23. Several reported separation s in the Post MSB6

- 2 population exceed fleet standard time in
service by more than 60%, weighting the cumulative distribution function.

24. The consolidated We ibull plot for the Post MSB6

- 2 population showed a characteristic shape factor significantly greater that previously reported for the other populations experiences thread fatigue failures.

25. For Post MSB6

- 2 population, f actors contributing to the altered cum ulative distribution
function include:

a. Incorrect reporting of the time in service for separated cylinders
b. Revised cylinder head casting with altered wall configuration

c. Variable and unknown field operating conditions resulting in the head barrel interface temperature exceeding the maximum design temperature limit of 375F

26. Risk calculations for the Post M SB6

- 2 population suggest only 5 % of the population is at significant risk of fatigue cracking in the head threads.

27. Post MSB6

- 2 population r isk project ion s in dicate 2 6 cylinder assemblies c ould fail over the next
twenty

- four months
28. Cylinders shipped through October 2009 assembled at design nominal interference will experience loss of all interference at the design maximum temperature of 375F.

29. Cylinders shipped through October 2009 assembled at design minimum interference will experience loss of all interference at an interface temperature of 325F
30. Cylinders shipped through October 2009 assembled at design maximum interference will retain positive interference thr ough 425FReport 1102

- 13

Page 64 31. Current production cylinder assemblies assembled at design nominal or maximum will retain positive interference through 425F

32. Current production cylinder assemblies assembled at design minimum interference will experience loss of all interference at the design maximum temperature of 375F
33. Press fit removal force estimates for cylinders shipped through October 2009 show:

a. Cylinders produced with maximum interference fit will carry about 75% of the
combustion force load at 300F and 25% of the combustio n force load at 375F.
b. Cylinders produced with the nominal interference fit will carry about 28% of the
combustion force load at 300F and 10% of the combustion force load at 350F.

c. Cylinders produced with minimum interference fit will transfer most of the co mbustion
load to the threads at a head

- barrel interface temperature of 300F and peak pressure of 900 psi.
34. Press fit removal force estimates for current production cylinders show:

a. Press fit conditions nominal, maximum, C3, and C4 will carry at least 50% of the combustion load through 375F.
b. The minimum fit condition will carry 20% of the combustion force load at 350F and 10%
of the load at 375F.

35. A suggested increase of assembly interference fit by 0.00 7

- inch shows all maximum, nominal,
and minimum interferenc e fit will withstand combustion loads through 425F.
36. Maximum contact pressure at maximum interference fit for the modified interface design do not exceed 14% of the yield stress of aluminum for between room temperature and 425F.
37. The statistical data and mechanical force calculations suggest head

- barrel interface temperature is less than 375F and/or peak combustion pressure is below 900 psi.

38. The preliminary Weibull cumulative distribution function for the repaired cylinder stripped
thread failure mode re sembles the cumulative distribution function for fatigue failure in the shrink band to dome transition radius. An in depth study of repaired cylinders will be required to make risk projections.



## Recommendations

1. We recommend establishing a system that would assign a sequential serial number to each cylinder assembly and other products that directly affect operational safety at the point of shipping. Under this recommendation, each serialized component or assembly would link to a product management database holding complete information on materials, processes, and inspections, complete information on all sub

- components used, and complete service history
information.

2. For those cylinders in population g roup SB4

- 1 rem aining in s e rvice, continue repetitive inspections as mandated by MSB6

- 2.
3. Remove remaining group SB4

- 1 cylinder assemblies in service at the next engine tear down or scheduled overhaul interval, whichever comes first.

4. For cylinder group SB6

- 2 we recommend continuing the MSB6

- 2 inspection program.Report 1102

- 13

Page 65 5. We suggest amending MSB6

- 2 to include visual inspections at fins 9

- 10 and 5

- 7 in addition to
fin 17.

6. We suggest amending MSB6

- 2 to require removal of these cylinders at the next engine tear

down or published li mits for time between overhauls, whichever is first.

7. We recommend including a clear statement in MSB6

- 2 precluding any repair and return to

service of cylinders affected by this service bulletin

. 8. For population g roup Post SB6

- 2 we suggest Issuing a mandato ry service bulleting calling for repetitive inspections of cylinders beginning at 250 hours.
9. We recommend issu ing a service bulletin for the Post SB6

- 2 group to include inspection for
cracks at fin 5

- 7 as well as fin 17.
10. We recommend removal all Pot MSB6

- 2 cylinders at the next engine teardown.

11. If records are available, we recommend identifying those Post MSB6

- 2 cylinders produced at the minimum interference fit and require their removal within the next 200

- hours.

12. Require removal of Post MSB6

- 2 cylinders consuming excessive oil for rehoning, reinstallation,
and break

- in to prevent excessive cylinder interface temperature.
13. .Conduct tests to directly measure head

- barrel interface temperature and peak combustion pressure of an operating TSIO

- 520NB at these suggested conditions:

a. Maximum manifold pressure, rated maximum cylinder head temperature
b. Maximum manifold pressure, rated maximum cylinder head temperature plus 25F

c. Maximum manifold pressure, rated maximum cylinder head temperature plus 50F

14. If measure d he ad

- barrel interface temperature exceeds 300F at maximum head temperature, consider issuing a service bulletin call for removal of current production cylinders produced at
minimum interference after 84 months or 700

- hours in service, replacing them with c ylinders having greater assembly interference.

15. Adjust assembly interference fit requirements to avoid transferring cyclic load into the threads

at a head

- barrel interface temperature corresponding to rated maximum head temperature plus 50F
16. As a precautio n, AE should produce current production cylinders with interference fit levels set
at nominal or above.

17. Pending definitive determination of the head

- barrel interface temperature corresponding to head temperatures up to 50F above maximum limit, AE should consider the feasibility of increasing assembly interference fit , preferably by 0.007

- inch

, to avoid load transfer to the threads up to 425F head

- barrel interface temperature.

18. Consider issuing a service guideline bulletin to all ECi customers explaining the necessity for:

a. proper break

- in of cylinders
b. inspection for and removal of cylinders incorrectly broken in

c. Inspection and restoration of all cooling baffles and devices to their properly certified configuration to minimize heat stress on the cylinder jointsReport 1102

- 13

Page 66 

## ATTACHMENT 1. FAA MDR AS OF 1/13/0 4, AEC631397 SEPARAT IONSReport 1102

- 13

Page 67 

## ATTACHMENT 2. TENSI LE STRENGTH

- TEMPERATURE GRAPH FO R A242.0

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000

50 100 150 200 250 300 350 400 450 500 550 600 650 Strength (psi)



## Temperature (F) Cast Alloy A242 T77 Tensile and Yield Strength

Ultimate

YieldReport 1102

- 13

Page 68 

## ATTACHMENT 3. THERM AL EXPANSION COEFFIC IENT FOR SAE4140 STE EL

7.05 7.10 7.15 

## 7.20 7.25 7.30 7.35 7.40 7.45 7.50 7.55 7.60 7.65 7.70

200 250 300 350 400 450 500 550 600 650 700 750 800 Expansion Coefficient E - 06 (in/in/F)



## Temperature Limit (F) SAE 4140 Average Thermal Expansion Coefficient from 68FReport 1102

- 13

Page 69 

## ATTACHMENT 4. COMPU TATION OF THE EFFECT IVE FRICTION COEFFICIENT

Push

- Off Test Data Provided by Airmotive Engineering

Characteristic Data Input

Head Configuration AEC631399 Rev. L

Barrel Configuration AEC634501 Rev. V

Machined Head Shrink Band Diameter Nominal Interference (in.) 5.458

Machined Head Shrink Band Diameter Maximum Interference (in.) 5.457

Machined Barrel Shrink Band Diameter Nominal Interference (in.) 5.4695

Machined Barrel Shrink Band Diameter Maximum Interference (in.) 5.472

Shrink Band contact Length (in.) 0.348

Interference, Diametrical (in) Interference, Radial (in.) Push

- Off Pressure (psi)

0.0115 0.0575 660

0.015 0.0075 1090



### Calculations for Friction Coefficient

HKL Nominal Interference Test

- Contact Pressure Calculation

Inner Modulus

- psi E 1 = 29000000

Inner Tensile Strength

- psi T S = 158700
Inner Yield Strength

- psi Y S1 = 142300

Inner Poisson's Ratio ν 1 = 0.3

Outer Modulus

- psi E 2 = 10300000
Outer Tensile Strength

- psi T S2 = 30000
Outer Yield Strength

- psi T S2 = 23000

Outer Poisson's Ratio ν 2 = 0.33
Contact Length

- in L = 0.348

Nominal Radius

- in r = 2.73475 Common Radius

Outer Radius

- in r o = 3.375 Outer Radius of Outer Tube

Outer Opening

- in r h = 2.729 Inner Radius of Outer TubeReport 1102

- 13

Page 70 Inner Surface

- in r s = 2.73475 Outer Radius of Inner Tube

Inner Opening

- in r i = 2.626 Inner Radius of Inner Tube

Radial Interference

- in δ = 0.00575

Contact Pressure

- lbs / sq in σ = 1
, 569



### HKL Maximum Interference Test

- Contact Pressure Calculation

Inner Modulus

- psi E 1 = 29000000
Inner Tensile Strength

- psi T S1 = 158700
Inner Yield Strength

- psi Y S1 = 142300

Inner Poisson's Ratio ν 1 = 0.3

Outer Modulus

- psi E 2 = 10300000
Outer Tensile Strength

- psi T S2 = 30000
Outer Yield Strength

- psi T S2 = 23000

Outer Poisson's Ratio ν 2 = 0.33
Contact Length

- in L = 0.348

Nominal Radius

- in r = 2.736

Outer Radius

- in r o = 3.375

Outer Opening

- in r h = 2.7285

Inner Surface

- in r s = 2.736

Inner Opening

- in r i = 2.626

Radial Interference

- in δ = 0.0075

Contact Pressure

- lbs / sq in σ = 2058



### Convert Push

- Off Pressure to Force

Nominal D iam e t ri

cal Interference (0.011 in.) Piston diameter (in) D = 5.25

Piston Area (sq. in.) A = 21.6754 Pressure (0.0115

- inch) P = 660 Force (lb) F = 14,287

Maximum Diamet r

ical Interference (0.015 in.) Piston diameter (in) D = 5.25

Piston Area (sq. in.) A = 21.64754 0 Pressure (0.0115

- inch) P = 1090 Force (lb) F = 23,596Report 1102

- 13

Page 71 

### Friction Coefficient Calculation

Nominal Diametrical Interference (0.0115

- inch) Contact Pressure (psi) σ = 1,569 From contact pressure calc's Engaged Length (inch) L = 0.3480 Insertion/Removal Force (lbs) F= 14,287 Nominal Radius (inch) r = 2.73475.
Friction Coefficient μ = 1.523065 Radial Interference (inch) δ = 0.00575 Maximum Diametrical Interference (0.015

- inch) Contact Pressure (psi) σ = 2,058 Engaged Length (inch) L = 0.3480 Insertion/Removal Force (lbs) F= 23,596 Nominal Radius (inch) r = 2.73600
Friction Coefficient μ = 1.916263
Radial Interference (inch) δ = 0.00750Report 1102

- 13

Page 72 

## ATTACHMENT 5 . THERMAL EXPANSION COMPUTATIONS

Note: All dimensions in inches.

Group Characteristic Temperature (F

68 300 350 375 400 425

H

- J

- K

- L Nominal: Nominal Interference Fit Thread Pitch and Shrink Band Diameters

Jnom 5.5530 5.5715 5.5743 5.5762 5.5781 5.5800

Jnom 5.5530 5.5715 5.5743 5.5762 5.5781 5.5800

Xnom 5.5645 5.5722 5.5757 5.5767 5.5777 5.5787
Ith 0.0115 0.0007 0.0014 0.0005

- 0.0004

- 0.0012

Hnom 5.4580 5.4742 5.4789 5.4808 5.4826 5.4845

Ynom 5.4695 5.4800 5.4805 5.4815 5.4824 5.4835
Isb 0.0115 0.0058 0.0015 0.0007

- 0.0002

- 0.0010

Δ 0.0000 0.0052 0.0002 0.0002 0.0002 0.0002

H

- J

- K

- L Condition 1: Maximum Interference Fit Thread Pitch and Shrink Band Diameters

Jmin 5.5520 5.5695 5.5733 5.5752 5.5771 5.5790

Xmax 5.5660 5.5752 5.5772 5.5782 5.5792 5.5801
Ith 0.0140 0.0057 0.0039 0.0030 0.0021 0.0012

Hmin 5.4570 5.4742 5.4779 5.4798 5.4816 5.4835

Ymax 5.4710 5.4800 5.4820 5.4830 5.4839 5.4850
Isb 0.0140 0.0058 0.0041 0.0032 0.0023 0.0015

Δ 0.0000 0.0001 0.0002 0.0002 0.0002 0.0003

H

- J

- K

- L Condition 2: Minimum Interference Fit thread Pitch and Shrink Band Diameters

Jmax 5.5540 5.5715 5.5753 5.5772 5.5791 5.5810

Xmin 5.5630 5.5722 5.5742 5.5752 5.5762 5.5772
Ith 0.0090 0.0007

- 0.0011

- 0.0020

- 0.0029

- 0.0037

Hmax 5.4590 5.4762 5.4799 5.4818 5.4836 5.4855

Ymin 5.4680 5.4770 5.4790 5.4800 5.4809 5.4820
Isb 0.0090 0.0008

- 0.0010

- 0.0018

- 0.0027

- 0.0035

Δ 0.0000 0.0001 0.0002 0.0002 0.0002 0.0002

Group Characteristic Temperature (F)

68 350 375 400 425

H

- J

- K

- L Condition 3: Max. Interference Fit Thread Pitch Dia. With Min. Interference Fit Shrink Band Dia

Jmin 5.5520 5.5733 5.5752 5.5771 5.5790

Xmax 5.5660 5.5772 5.5782 5.5792 5.5802
Ith 0.0140 0.0039 0.0030 0.0021 0.0013

Hmax 5.4590 5.4799 5.4818 5.4836 5.4855
Ymin 5.4680 5.4790 5.4800 5.4809 5.4820
Isb 0.0090

- 0.0010

- 0.0018

- 0.0027

- 0.0035

Δ

- 0.0050

- 0.0048

- 0.0048

- 0.0048

- 0.0048

H

- J

- K

- L Condition 4: Min. Interference Fit Thread Pitch Dia. with Max

. Interference Shrink Band Dia

Jmax 5.5540 5.5753 5.5772 5.5791 5.5810Report 1102

- 13

Page 73 Xmin 5.5630 5.5742 5.5752 5.5762 5.5772
Ith 0.0090

- 0.0011

- 0.0020

- 0.0029

- 0.0037
Hmin 5.4570 5.4779 5.4798 5.4816 5.4835

Ymax 5.4710 5.4820 5.4830 5.4839 5.4850
Isb 0.0140 0.0041 0.0032 0.0023 0.0015

Δ 0.0050 0.0052 0.0052 0.0052 0.0052

Group Characteristic Temperature (F)

68 350 375 400 425 Group N Nominal: Nominal Interference Fit Thread Pitch and Shrink Band Diameters

Jnom 5.5510 5.5723 5.5742 5.5761 5.5780

Xnom 5.5645 5.5757 5.5767 5.5777 5.5787
Ith 0.0135 0.0034 0.0025 0.0016 0.0008

Hnom 5.4520 5.4729 5.4748 5.4766 5.4785

Ynom 5.4695 5.4805 5.4815 5.4824 5.4835
Isb 0.0175 0.0076 0.0067 0.0058 0.0050

Δ 0.0040 0.0042 0.0042 0.0042 0.0042 Group N Condition 1: Maximum Interference Fit Thread Pitch and Shrink Band Diameters

Jmin 5.5500 5.5713 5.5732 5.5751 5.5769

Xmax 5.5660 5.5772 5.5782 5.5792 5.5802
Ith 0.0160 0.0059 0.0050 0.0041 0.0033
Hmin 5.4510 5.4719 5.4738 5.4756 5.4775

Ymax 5.4710 5.4820 5.4830 5.4839 5.4850
Isb 0.0200 0.0101 0.0092 0.0083 0.0075

Δ 0.0040 0.0042 0.0042 0.0042 0.0042 Group N Condition 2: Minimum Interference Fit thread Pitch and Shrink Band Diameters

Jmax 5.5520 5.5733 5.5752 5.5771 5.5790
Xmin 5.5630 5.5742 5.5752 5.5762 5.5772
Ith 0.0110 0.0009 0.0000

- 0.0009

- 0.0017

Hmax 5.4530 5.4739 5.4758 5.4776 5.4795

Ymin 5.4680 5.4790 5.4800 5.4809 5.4820
Isb 0.0150 0.0051 0.0042 0.0033 0.0025

Δ 0.0040 0.0042 0.0042 0.0042 0.0042 Group N Condition 3: Max. Interference Fit Thread Pitch Dia. With Min. Interference Fit Shrink Band Dia

Jmin 5.5500 5.5713 5.5732 5.5751 5.5769

Xmax 5.5660 5.5772 5.5782 5.5792 5.5802
Ith 0.0160 0.0059 0.0050 0.0041 0.0033

Hmax 5.4530 5.4739 5.4758 5.4776 5.4795

Ymin 5.4680 5.4790 5.4800 5.4809 5.4820
Isb 0.0150 0.0051 0.0042 0.0033 0.0025

Δ

- 0.0010

- 0.0008

- 0.0008

- 0.0008

- 0.0008 Group N Condition 4: Min. Interference Fit Thread Pitch Dia. with Max

. Interference Shrink Band Dia

Jmax 5.5520 5.5733 5.5752 5.5771 5.5790Report 1102

- 13

Page 74 Xmin 5.5630 5.5742 5.5752 5.5762 5.5772
Ith 0.0110 0.0009 0.0000

- 0.0009

- 0.0017

Hmin 5.4510 5.4719 5.4738 5.4756 5.4775

Ymax 5.4710 5.4820 5.4830 5.4839 5.4850
Isb 0.0200 0.0101 0.0092 0.0083 0.0075

Δ 0.0090 0.0092 0.0092 0.0092 0.0093 Group Characteristic Temperature (F)

68 350 375 400 425

N+004 Nominal: Nominal Interference Fit Thread Pitch and Shrink Band Diameters

Jnom 5.54700 5.57016 5.57205 5.57393

Xnom 5.56450 5.57666 5.57765 5.5787
Ith 0.01750 0.00650 0.00561 0.00481

Hnom 5.44800 5.47075 5.47260 5.47445

Ynom 5.46950 5.48146 5.48243 5.4835
Isb 0.02150 0.01071 0.00983 0.00905

Δ 0.00400 0.00421 0.00422 0.00424
N+004 Condition 1: Maximum Interference Fit Thread Pitch and Shrink Band Diameters

Jmin 5.54600 5.56916 5.57104 5.57293

Xmax 5.56600 5.57820 5.57920 5.5802
Ith 0.02000 0.00904 0.00816 0.00727
Hmin 5.44700 5.46974 5.47159 5.47345

Ymax 5.47100 5.48296 5.48393 5.48500
Isb 0.02400 0.01322 0.01234 0.01156

Δ 0.00400 0.00417 0.00418 0.00428
N+004 Condition 2: Minimum Interference Fit thread Pitch and Shrink Band Diameters

Jmax 5.54800 5.57116 5.57305 5.57494
Xmin 5.56300 5.57520 5.57620 5.57724
Ith 0.01500 0.00404 0.00315 0.00230

Hmax 5.44900 5.47175 5.47360 5.47546
Ymin 5.46800 5.47995 5.48093 5.481996
Isb 0.01900 0.00820 0.00732 0.00654

Δ 0.00417 0.00417 0.00424 Group Characteristic Temperature (F)

68 350 375 400 425

N +009 Nominal: Nominal Interference Fit Thread Pitch and Shrink Band Diameters

Jnom 5.54200 5.56514 5.56702 5.56891

Xnom 5.56450 5.57666 5.57765 5.57874
Ith 0.02250 0.01152 0.01063 0.00984

Hnom 5.44300 5.46573 5.46758 5.46943

Ynom 5.46950 5.48146 5.48243 5.48350
Isb 0.02650 0.01573 0.01485 0.01407

Δ 0.00400 0.00421 0.00422 0.00424

N+009 Condition 1: Maximum Interference Fit Thread Pitch and Shrink Band DiametersReport 1102

- 13

Page 75 Jmin 5.54100 5.56413 5.56602 5.56790

Xmax 5.56600 5.57820 5.57920 5.5802
Ith 0.02500 0.01407 0.01318 0.01230
Hmin 5.44200 5.46472 5.46657 5.46842

Ymax 5.47100 5.48300 5.48390 5.485
Isb 0.02900 0.01828 0.01733 0.01658

Δ 0.00400 0.00421 0.00415 0.00428
N+009 Condition 2: Minimum Interference Fit thread Pitch and Shrink Band Diameters

Jmax 5.54300 5.56614 5.56803 5.56991
Xmin 5.56300 5.57520 5.57620 5.57724
Ith 0.02000 0.00906 0.00817 0.00733

Hmax 5.44400 5.46673 5.46858 5.47043
Ymin 5.46800 5.47995 5.48093 5.481996
Isb 0.02400 0.01322 0.01234 0.01156

Δ 0.00400 0.00417 0.00417 0.00424Report 1102

- 13

Page 76 

## ATTACHMENT 6

. REMOVAL FORCE GRAPHI CAL SUMMARY NOMINAL,

MAXIMUM, AND MINIMUM FIT CONDITONS

0 5,000 10,000 15,000 20,000 25,000 30,000 

### 35,000 40,000 45,000 50,000

50 100 150 200 250 300 350 400 450 Removal Force (lb)



## Interface Temperature (F)



# HJKL Nominal Inerferference Fit

Force SB Force Threads Total forceReport 1102

- 13

Page 77 

### 0 10,000 20,000 30,000 40,000 50,000 60,000 70,000

50 100 150 200 250 300 350 400 450 Removal Force (lb)



## Interface Temperature (F) HJKL Condition 1

- Maximum Interference Fit

Force SB Force Threads Total forceReport 1102

- 13

Page 78 

### 0 4,000 8,000 12,000 16,000 20,000 24,000 28,000 32,000

50 100 150 200 250 300 350 400 450 Removal Force (lb)



## Interface Temperature (F) HJKL Conditon 2

- Minimum Interference Fit

Force SB Force Threads Total forceReport 1102

- 13

Page 79 

### 0 10,000 20,000 30,000 40,000 50,000 60,000 

### 70,000 80,000



### 50 100 150 200 250 300 350 400 450 Removal Force (lb)



## Interface Temperature (F)



# N Nominal Interference

Force SB Force Threads Total ForceReport 1102

- 13

Page 80 

### 0 10,000 20,000 30,000 40,000 50,000 60,000 

### 70,000 80,000 90,000 100,000 110,000

50 100 150 200 250 300 350 400 450 Remvoal Force (lb)



## Interface Temperature (F) N Condition 1

- Maximum Interference

Force SB Force Threads Total ForceReport 1102

- 13

Page 81 

### 0 10,000 20,000 

### 30,000 40,000 50,000 60,000

50 100 150 200 250 300 350 400 450 Removal Force (lb)



# Interface Temperature (F) N Condition 2

- Minimum Interference

Force SB Force Threads Total ForceReport 1102

- 13

Page 82 

### 0 20,000 40,000 

### 60,000 80,000 100,000 120,000 140,000



### 50 100 150 200 250 300 350 400 450 Removal force (lb)



## Interface Temperature (F)



## N+004 Nominal Interference

Force SB Force Threads Total ForceReport 1102

- 13

Page 83 

### 0 20,000 40,000 

### 60,000 80,000 100,000 120,000 

### 140,000 160,000

50 100 150 200 250 300 350 400 450 Removal Force (lb)



## Inteface Temperature (F) 

## N+004 Condition C1

- Maximum Interference

Force SB Force Threads Total ForceReport 1102

- 13

Page 84 

### 0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 90,000 100,000

50 100 150 200 250 300 350 400 450 Removal force (lb)



## Interface Temperature (F) 

## N+004 Condition 2

- Minimum Interference

Force SB Force Threads Total ForceReport 1102

- 13

Page 85 

### 0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000 180,000 200,000 220,000 240,000



### 50 100 150 200 250 300 350 400 450 Removal Force (lb)



### Interface Temperature (F)



## N+009 Nominal Interference

Force SB Force Threads Total ForceReport 1102

- 13

Page 86 

### 0 20,000 40,000 60,000 80,000 100,000 120,000 

### 140,000 160,000 180,000 200,000 220,000 240,000 260,000

50 100 150 200 250 300 350 400 450 Removal Force (lb)



## Interface Temperature (F) 

# N+009 Condition 1

- Maximum Interference

Force SB Force Threads Total ForceReport 1102

- 13

Page 87 

### 0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000

50 100 150 200 250 300 350 400 450 Removal Force (lb)



## Interface Temperature (F) N+009 Condition 2

- Minimum Interference

Force SB Force Threads Total ForceReport 1102

- 13

Page 88 

## REFERENCES

1 Abernethy, Robert B., The New Weibull handbook, Fifth Edition, ©2004

2 Kenton, D. Airmotive engineering Report 0905

- 1, AEL65102 Cylinder Weibull Analysis, 5/19/09

3 Exce lcalcs, PressFits.xls, downloaded from ExcelCalcs.com 2/28/11

4 Private communication, David Shear, Precision Machined Airparts Subsidiary of Danbury Aerospace, January 25, 2011

5 Private communication, Pete Hakala, ASW

- 190, February, 16, 2011

6 Type Certificate E8CE Rev. 21, Teledyne Continental Motors, Mobile, Alabama

7 Al

- 202, Aluminum 242.0 Alloy T77 Condition, Alloy Digest, ASM International, ©2002

8 Al

- 25, Aluminum 4032 Alloy, Alloy Digest, ASM International, ©2002

9 SA371, ESR4140 Steel, A lloy digest, ASM International ©2002

10 Private communication, Bob Carlton, Danbury Aerospace, March 28,2011

11 Private communication, Jimmy Tubbs, Danbury A e rospace, February 28, 2011

12 Kaufnab, J. Gilber, and Rooy, Elvin L., Aluminum Alloy Castings, ASM In ternational ©2005