U,S, Deportment 

of Transportation 

Federal Aviation 

Administration 

MAY 1 2 2011 

Air lndia 

Engine and Propeller Directorate 

ATTN: Jagadeesan Umamaheswaran 

Engine Overhaul Department 

Air India Santacruz East 

Mumbai, Maharashtra 

India, 400029 

Dear Mr. Umamaheswaran: 

Engine Certification Office 

12 New England Executive Park 

Burlinglon, MA 01803 

(781) 238-7140, Fax: (781) 238-7199 

The Federal Aviation Administration (FAA) receiv d your question that you have submitted 

via the docket F AA-201 0-0068, regarding the FAA Airworthiness Directive (AD) 

2011-02-07. 

A fier a careful review of your question, we have fo 

to AD 2011-02-07. 

Please, find enclosed the summary of all public COl 

regarding this AD with the FAA responses. 

Sincerely, 

' { ..,."' '' ~- ~J<.A.. O, ''----_ 

Tomasz Rakowski 

Engineer, Engine Certification Office 

Federal Aviation Administration 

nd r infomlation warranting a change 

llents to AD 2011-02-07 and questions 

Enclosure: Summary of FAA Responses to Public Comments and Questions Regarding 

AD 2011-02-07 Final Rul e - Request for Comments 
U.s. Department 

of Transportation 

Federal Aviation 

Administration 

MA'< 1 2 ZO\l 

Engine and Propeller Oirectorat 

Biman Bangladesh Airlines Limited 

ATTN: Ehsanul Haque 

Central Engineering 

Biman Engineering Hangar Complex 

Hazrat Shahjalal International Airport. 

Dhaka, Bangladesh, 1229 

Dear Mr. Haque: 

The Federal Aviation Administration (FAA) recei 

via the docket FAA-2010-0068, regarding the FA 

2011-02-07. 

Engine Certification Office 

12 New England Executive Park 

Burlington, MA 01803 

(781) 238-7140, Fax: (781) 238-7199 

d Y\lur comment that you have submitted 

AirWorthiness Directive (AD) 

After a careful review of your comment, we have fi un no information warranting a change 

to AD 2011-02-07. 

Please, find enclosed the summary of all public co ne , ts to AD 2011-02-07 and questions 

regarding this AD with the FAA responses. 

Sincerely, 

1~ 

Tomasz Rakowski 

Engineer, Engine Certification Office 

Federal Aviation Administration 

Enclosure: Summary of FAA Responses to Pub ic omments and Questions Regarding 

AD 2011-02-07 Final Rule - Reque t fo Comments 
U,S, Department 

of Transportation 

Federal Aviation 

Administration 

MAY 1 2 ZO\1 

Engine and Propeller Directorate 

Boeing Commercial Airplanes 

ATTN: Randy Johnstone 

3855 N Lakewood Blvd 

Long Beach, CA 90846 

Dear M r. Johnstone: 

Engine Certification Office 

12 New England Executive Park 

Burlington, MA 01803 

(781) 238-7140, Fax: (781) 238-7199 

The Federal Aviation Administration (FAA) receiv d your comment that you have submitted 

via the docket FAA-2010-0068, regarding the FAA Ainr0rthiness Directive (AD) 

2011 -02-07. 

After a careful review of your comment, we have D und r o information warranting a change 

to AD 2011-02-07. 

Please, find enclosed the summary of all public con ments to AD 2011-02-07 and questions 

regarding this AD with the FAA responses. 

Sincerely, 

~""__ ~_k .... ~~_ 

Tomasz Rakowski 

Engineer, Engine Certification Office 

Federal Aviation Administration 

Enclosure: Summary of FAA Responses to Pub ic Comments and Questions Regarding 

AD 2011-02-07 Final Rule - Reque t for Comments 
U.S. Deportment 

of Transportation 

Federal Aviation 

Administration 

MAY 1 2 2011 

Engine and Propeller Directorat 

Hong Kong Aircraft Engineeri ng Co. Ltd. 

ATTN: Thomas W. K. Lai 

80 South Perimeter Road 

HK International Airport 

Lantau, Hong Kong 

Dear Mr. Lai: 

Engine Certification Office 

12 New England Executive Park 

Burlington, MA 01803 

(781) 238-7140, Fax: (781) 238-7199 

The Federal Aviation Administration (FAA) recei d your comments and questions that you 

have submitted via the docket FAA-2010-0068, re ardihg the FAA Airworthiness Directive 

(AD) 2011-02-07. 

After a careful review of your comments, we have ount! no inforn1ation warranting a change 

to AD 2011 -02-07. 

Please, find enclosed the summary of all public co 

regarding this AD with the FAA responses. 

Sincerely, 

~ 

IQ~ (.2=.9..,,-"-, 0_ 

Tomasz Rakowski 

Engineer, Engine Certification Office 

Federal Aviation Administration 

ents to AD 2011 -02-07 and questions 

Enclosure: Summary of FAA Responses to Pub ic omments and Questions Regarding 

AD 2011-02-07 Final Rule - Reque t fo Comments 
Summary of FAA Responses to Public Comments and Questions Regarding AD 2011-02-07 Final Rule – Request for Comments 

Page 1 of 5 

Summary of FAA Responses to Public Comments and Questions 

Regarding AD 2011-02-07 Final Rule – Request for Comments 

Applicability in paragraph (c)(2)

Comment: One commenter, Boeing Commercial Airplanes, stated in docket document 

FAA-2010-0068-0018 that AD 2011-02-07 was applicable to DC-10 series airplanes 

equipped with CF6-50 series engines installed: DC-10-15, DC-10-30, DC-10-30F, 

KC-10, KDC-10, and MD-10-30F. 

FAA Disposition: At this time we are not planning to change paragraph (c)(2) of AD 

2011-02-07 to include this comment, as this paragraph is not all-inclusive and is for 

informational purposed only. 

Conditional borescope inspection (BSI) of high-pressure turbine (HPT) blades per 

paragraph (f)(3)

Comment: Two commenters proposed via email that the requirements of paragraph 

(f)(3) in conjunction with items (iv) and (v) in Table 2 of AD 2011-02-07 be changed so 

BSI of HPT blades is required only if an engine experiences two consecutive raw exhaust 

gas temperature (EGT) trend data points that exceed the EGT levels specified in the AD, 

and the increase in the raw EGT trend data points is not confirmed by a corresponding 

increase in the raw fuel flow or fan speed/core speed (N1/N2) relationship (e.g. due to an 

EGT indication error, TAT error, pneumatic loading variations, or unusual altitude 

operations). 

FAA Disposition: At this time, we are not planning to change the AD with regards to 

paragraph (f)(3) requirements. We could however consider an AMOC to AD 2011-02-07, 

paragraph (f)(3), if requested and substantiated to show that the level of safety mandated 

by the AD can be maintained if for certain conditions the EGT data exceeding the rolling 

average could be disregarded. 

Waiving repetitive engine core vibration survey requirements of paragraph (p)

Comment: One commenter, Biman Bangladesh Airlines Limited, requested in docket 

document FAA-2010-0068-0017 the requirements for repetitive engine core vibration 

survey be waived for the operators of aircraft equipped with Airborne Vibration 

Monitoring (AVM) system and performing Engine Condition Trend Monitoring. 

FAA Disposition: The intent of paragraph (p) of AD 2011-02-07 is for the operator of 

applicable engines to perform repetitive engine core vibration surveys regardless of the 

condition of the engine system, complementary to any engine health programs. At this 

point, we are not planning to waive or alter the requirements of paragraph (p). However, 

you may request an AMOC to this paragraph to extend the survey intervals, if you can 

show that the level of safety mandated by the AD can be maintained with the engine 

health programs you are performing. 

Revising of GE CF6-50 S/B 72-1313 Revision 1

Comment: One commenter, Hong Kong Aircraft Engineering Co. Ltd., proposed in 

docket document FAA-2010-0068-0011, that GE CF6-50 S/B 72-1313 Revision 1, be 

revised to recommend repetitive engine core vibration surveys and be incorporated by 

reference in AD 2011-02-07. 
Summary of FAA Responses to Public Comments and Questions Regarding AD 2011-02-07 Final Rule – Request for Comments 

Page 2 of 5 

FAA Disposition: Engine manufacturers own their service bulletins. We approve the 

technical content (data) in those documents. Suggestions regarding alterations to GE 

service bulletins should be addressed to GE directly. At this time, we are not planning to 

incorporate GE CF6-50 S/B 72-1313 by reference in AD 2011-02-07. This bulletin is 

referenced in the AD only as guidance for the operators. 

Amendment for the FPI requirements

Comment: One commenter proposed via email that the FPI of low-pressure turbine 

(LPT) stage 3 disk forward spacer arm be performed without disassembling the LPT rotor 

down to piece part level. 

FAA Disposition: The inner diameter of the installed LPT stage 3 disk forward spacer 

arm is not accessible for a proper cleaning and FPI, and therefore requires disassembly of 

the part from its module/rotor. At this time, we are not planning to amend this 

requirement. 

Requirements for fluorescent penetrant inspection (FPI) of the LPT stage 3 disk per 

paragraph (g)

Question: One commenter, Hong Kong Aircraft Engineering Co. Ltd., in docket 

documents FAA-2010-0068-0011 and FAA-2010-0068-0014, and seven commenters via 

email, asked what were the pass/fail criteria for BSI of the HPT stage 1 and stage 2 

blades required in paragraph (f) of AD 2011-02-07. 

Response: The intent of paragraph (g) of AD 2011-02-07, is for the operator of 

applicable engines to perform the FPI of LPT stage 3 disk forward spacer arm inner 

diameter if the engine fails any of the BSI of HPT rotor stage 1 or stage 2 blades, 

required by paragraph (f) of this AD. Then, if FPI reveals cracks of band of fluorescence, 

such disk must be removed from service. The limits for the HPT stage 1 and stage 2 blade 

borescope inspections are defined in the applicable Airframe Maintenance Manual 

(AMM). If the Manual does not define limits in certain areas of the airfoil, damage in 

these areas would not require an action (i.e. FPI of LPT stage 3 disk) per this AD. 

Ultrasonic inspection (UI) as means of compliance with paragraph (f)

Question: One commenter, Hong Kong Aircraft Engineering Co. Ltd., asked in docket 

document FAA-2010-0068-0011 if the UI of the LPT stage 3 disk forward spacer arm per 

General Electric Company (GE) CF6-50 Service Bulletin (S/B) 72-1312 Revision 1 be an 

acceptable equivalent of the FPI to meet the requirements of AD 2011-02-07. 

FAA Response: Ultrasonic inspection is not considered an acceptable means of meeting 

the requirements of paragraph (f) of this AD. 

Limits for BSI per paragraph (f)

Question: One commenter, Hong Kong Aircraft Engineering Co. Ltd., asked in docket 

document FAA-2010-0068-0014 if the BSI pass/fail limit criteria in AD 2010-06-15 were 

applicable to BSI required by AD 2011-02-07. 

FAA Response: AD 2010-06-15 was superseded by AD 2010-12-10, which was 

ultimately superseded by AD 2011-02-07. The requirements of the superseded ADs (i.e. 

2010-06-15 and 2010-12-10) are no longer in effect. Use the applicable AMM limits for 
Summary of FAA Responses to Public Comments and Questions Regarding AD 2011-02-07 Final Rule – Request for Comments 

Page 3 of 5 

pass/fail criteria for the borescope inspection required in paragraph (f) of AD 

2011-02-07. 

EGT thermocouple probe inspections per paragraphs (h) and (i)

Question: One commenter, Hong Kong Aircraft Engineering Co. Ltd., in docket 

document FAA-2010-0068-0011 and one commenter via email asked what was the 

procedure for EGT thermocouple probe inspections required by AD 2011-02-07. 

FAA Response: The intent of paragraphs (h) and (i) of AD 2011-02-07 is for the 

operator of applicable engine to determine the level of wear caused by contact between 

the clocked turbine mid-frame (TMF) liner and the EGT thermocouple probes. The TMF 

liner clocking inspections per applicable AMM are appropriate inspection procedures to 

meet the requirements of these paragraphs. A visual inspection of the probe is sufficient, 

however it would require pulling the probe out of the engine, because a visual check (e.g. 

via borescope) of the installed probe would not fully show the wear damage. Note that 

GE CF6-50 S/B 72-1307 Revision 1 calls for applicable AMM. All operations for TMF 

liner clocking inspections must be performed if required by applicable AMM. 

EGT system resistance check inspections per paragraphs (k) and (l)

Question: One commenter, Hong Kong Aircraft Engineering Co. Ltd., asked in docket 

document FAA-2010-0068-0011 what was the procedure for EGT system resistance 

check inspection required by AD 2011-02-07. 

FAA Response: AMM applicable to the airframe should be referenced for the EGT 

system resistance check inspections per paragraphs (k) and (l) of AD 2011-02-07. Note 

that GE CF6-50 S/B 72-1307 Revision 1 calls for applicable AMM. 

Alternate means of meeting requirements of paragraph (n)

Question: One commenter, Hong Kong Aircraft Engineering Co. Ltd., in docket 

document FAA-2010-0068-0011 and four commenters via email asked if the one-time UI 

of the LPT stage 3 disk forward spacer arm required by AD 2011-02-07 could be 

accomplished by performing GE CF6-50 S/B 72-1309 Revision 1, and if FPI was 

equivalent to UI. Moreover, one commenter, Air India, asked in document FAA-2010-

0068-0012 if the one-time ultrasonic inspection of the LPT stage 3 disk forward spacer 

arm is required if the disk has just been FPI inspected and is pending installation. 

FAA Response: The intent of paragraph (n) of AD 2011-02-07 is for the operator of 

applicable engine to perform, within 75 cycles after the effective date of this AD, a onetime UI of the LPT stage 3 disk forward spacer arm per paragraphs E through K of 

Appendix A of GE CF6-50 S/B 72-1312 Revision 1. Per paragraph (y) of this AD, this 

inspection requirement may be satisfied if an UI was performed before the effective date 

of this AD using paragraphs E through K of Appendix A of SBs No. 72-1312 or 72-1312 

Revision 1. The requirements of paragraph (n) of this AD are not automatically met by 

accomplishing GE CF6-50 SB 72-1309, i.e. by FPI inspection. You may however request 

an alternative method of compliance (AMOC) for the engines that have complied with 

GE CF6-50 S/B 72-1309 after the 3rd of June, 2010 to satisfy paragraph (n) of this AD. 

Such an AMOC request may propose performing a piece part level FPI of the LPT stage 

3 disk, to satisfy paragraph (n) of this AD. 
Summary of FAA Responses to Public Comments and Questions Regarding AD 2011-02-07 Final Rule – Request for Comments 

Page 4 of 5 

Alternate means of meeting requirements of paragraph (r)

Question: One commenter, Hong Kong Aircraft Engineering Co. Ltd., asked in docket 

document FAA-2010-0068-0011 if on-wing UI of LPT stage 3 disk can be performed per 

GE CF6-50 S/B 72-1312 Revision 1 instead of FPI to meet requirements of paragraph (r) 

of this AD. 

FAA Response: No. A failed engine core vibration survey requires FPI of LPT stage 3 

disk forward spacer arm before returning the engine to service. 

Engine test cell runs to meet requirements of paragraph (o)

Question: One commenter asked via email if before installation after the shop visit the 

engine core vibration survey requirement of paragraph (o) can be met by the full engine 

test cell performance run and meeting vibration limits per the Engine Manual (EM). 

FAA Response: The intent of paragraph (o) of AD 2011-02-07 is for the operator of 

applicable engines to perform an initial engine core vibration survey within 75 cycles 

after the effective date of this AD with survey parameters set as required by paragraphs 

(o)(1) and (o)(2) of this AD. Per paragraph (z) of this AD, this initial inspection 

requirement may be satisfied if an engine core vibration survey was performed before the 

effective date of this AD using GE CF6-50 S/Bs No. 72-1313 or 72-1313 Revision 1 

within engine's last 350 cycles. The requirements of paragraph (o) are not automatically 

met by passing the EM vibration survey in a test cell. You may however request an 

AMOC for the engines that have been installed onto aircraft after the 3rd of June, 2010, 

which have passed the EM vibration survey requirements in an approved test cell and 

have not accumulated any engine flight cycles nor had a shop visit between subject test 

cell vibration survey and engine installation, to satisfy paragraph (o) of this AD. 

Reported vibrations requiring engine core vibration survey per paragraph (s)

Question: One commenter asked via email if there was defined a level of vibrations that 

would trigger the engine core vibration survey per requirements of paragraph (s). 

FAA Response: The intent of paragraph (s) of AD 2011-02-07 is to perform the engine 

core vibration survey per paragraphs (o)(1) through (o)(2) if the maintenance crew or the 

flight crew report engine vibrations that are suspected to be caused by the HPT rotor. The 

indicated core vibration levels are defined in appropriate AMM. 

Reporting requirements of paragraph (u)

Question: Two commenters asked via email if the requirements of paragraph (u)(1) for 

reporting of cracks is applicable to cracks on borescope inspected HPT blades, if there is 

a template for the reports, and if all failed disks or only cracked disks should be reported. 

FAA Response: The intent of paragraph (u)(1) of AD 2011-02-07 is to request the 

operator of applicable engine to report any cracks or circumferential bands of 

fluorescence found on LPT stage 3 disk forward spacer arms. Although, there is no 

required format of such report, it should at least determine engine serial number, affected 

disk part number and serial number, and cycles since new and since the last inspection. 

Note that we also requested reporting of failed UIs of LPT stage 3 disk and failed engine 

core vibration surveys in paragraphs (u)(2) and (u)(3), respectively. 
Summary of FAA Responses to Public Comments and Questions Regarding AD 2011-02-07 Final Rule – Request for Comments 

Page 5 of 5 

Previous credit per paragraph (aa)

Question: Two commenters asked via email if they were required to perform the initial 

BSI per paragraph (f)(1) of AD 2011-02-07 if they had been granted AMOCs to AD 

2010-12-10 approving extended BSI intervals. 

FAA Response: Per paragraph (aa) of AD 2011-02-07, the AMOC to AD 2010-12-10 

paragraph (g) that we granted you is still valid. You can use the extended cycle intervals 

for borescope inspections to comply with AD 2011-02-07, paragraph (f) requirements. 

The engines that have been borescope inspected per AD 2010-12-10 paragraph (g) within 

the last approved extended number of cycles do not need to be "initial" borescope 

inspected. 

AMOC for inspection intervals

Question: Two commenters asked via email if extending the inspection intervals of AD 

2011-02-07 is possible, and in what circumstances. 

FAA Response: You can request an AMOC to any mandatory requirement of AD 2011-

02-07, if you find a different way to comply with the actions specified in this AD. We 

will grant you such AMOC, if your proposal provides an acceptable level of safety. 

Please, refer to 14 CFR Part 39.19 and FAA Order 8110.103A for details on AMOCs.