Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan Engines

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 95-ANE-57; Amendment 39-9853; AD 96-25-10]

RIN 2120-AA64

Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan

Engines

AGENCY: Federal Aviation Administration, DOT.

[[Page 66893]]

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD),

applicable to Pratt & Whitney JT9D series turbofan engines, that

requires installing an improved design turbine exhaust case (TEC) with

a thicker containment wall, modifying the existing TEC to incorporate a

containment shield, or modifying the existing TEC to replace the ``P''

flange and case wall. This amendment is prompted by reports of 64

uncontained engine failures since 1972. The actions specified by this

AD are intended to prevent release of uncontained debris from the TEC

following an internal engine failure, which can result in damage to the

aircraft.

DATES: Effective February 18, 1997.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of February 18, 1997.

ADDRESSES: The service information referenced in this AD may be

obtained from Pratt & Whitney, Publications Department, Supervisor

Technical Publications Distribution, M/S 132-30, 400 Main St., East

Hartford, CT 06108; telephone (860) 565-7700, fax (860) 565-4503. This

information may be examined at the Federal Aviation Administration

(FAA), New England Region, Office of the Assistant Chief Counsel, 12

New England Executive Park, Burlington, MA; or at the Office of the

Federal Register, 800 North Capitol Street, NW., suite 700, Washington,

DC.

FOR FURTHER INFORMATION CONTACT: Daniel Kerman, Aerospace Engineer,

Engine Certification Office, FAA, Engine and Propeller Directorate, 12

New England Executive Park, Burlington, MA 01803-5299; telephone (617)

238-7130, fax (617) 238-7199.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal

Aviation Regulations (14 CFR part 39) to include an airworthiness

directive (AD) that is applicable to Pratt & Whitney (PW) JT9D series

turbofan engines was published in the Federal Register on June 5, 1996

(61 FR 28520). That action proposed to require installing an improved

design turbine exhaust case (TEC) with a thicker containment wall,

modifying the existing TEC to incorporate a containment shield, or

modifying the existing TEC to replace the ``P'' flange and case wall.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comments received.

One commenter states that the proposed modification of the TEC as a

solution to preventing uncontained engine failure is unnecessary since

there are modifications and inspection programs available that

specifically address the root causes for those events that led to

uncontained engine failures. The commenter points out that of the 64

incidents of TEC penetration, all but one event are addressed by other

mandated actions. The FAA does not concur. Since January 1993, when the

FAA first considered issuance of an AD for TEC containment, three

additional conditions have occurred that the FAA considers warranting

AD action at this time. First, there have been new root cause problems

resulting in TEC penetrations; second the rate of uncontained engine

failures has increased; and third, more substantial damage to the

engine and aircraft has occurred. The discovery of new root causes of

failures demonstrates that failures and subsequent uncontainments

result from a wider variety of reasons than previously believed. The

causal factors for these uncontainments include maintenance, design

deficiencies, manufacturing defects, corrosion, foreign object damage,

etc. The FAA has determined that even with the best available

strategies for addressing the root cause of engine failures, the FAA

expects that new failure modes and failure sequences could exist. As a

result, the FAA anticipates further challenges to the TEC containment

structure, and has determined that the necessary containment

modifications must be implemented through an AD as proposed.

In response to the comment that the root cause of all but one of

the 64 referenced uncontained events are addressed by current mandatory

action, the FAA does not concur. Additional review of the TEC

penetration history reveals multiple incidents in which the root cause

was undetermined, or in which no mandatory action by AD is required, or

in which operators inadvertently did not comply with AD action, or in

which improper repair or inspection was performed on certain engine

components.

One commenter states that a probabilistic risk assessment

accomplished by PW in October 1995 concludes that there is insufficient

risk to mandate TEC modification. The FAA does not concur. The risk

assessment performed by PW is a structured approach that enables the

FAA to better assess and target critical areas and prioritize

resources. It is also necessary to emphasize that risk assessment is

not the only means of determining the need for mandatory corrective

action, and that other parameters such as incidence rate, failure

modes, restoration of certification basis, and basic engineering

judgment are also utilized. The FAA has determined that for the TEC

penetration issue all these other factors result in the need to issue

an AD.

One commenter states that the FAA cost assessment of approximately

$2,500 per engine to accomplish the proposed actions is based on the

accomplishment of the option to weld shields to provide increased wall

thickness. For some operators this is not a preferred option. The FAA

concurs in part. The FAA has provided industry three options for

compliance with the proposed AD. These options, in terms of decreasing

cost, are as follows: a new thick wall TEC, a modified TEC with a new,

thicker ``P'' flange, and finally welding on containment shields.

Several operators have expressed concern with the durability of the

welded containment shields option and take exception to the fact that

the FAA utilized this option for the AD cost assessment. This operator

plans to utilize one of the more costly methods for compliance with the

AD. The FAA has reviewed all three options for enhanced containment and

concludes that all three satisfy Part 33 of the Federal Aviation

Regulations (FAR) (14 CFR part 33) requirements. The FAA performed the

cost assessment utilizing the containment shield option since it has

the least economic impact, and the FAA has reason to believe that the

majority of operators will utilize this option, which has sound design

and durability in accordance with FAR Part 33. The FAA understands that

a new case would have greater longevity, and that the new ``P'' flange

may be necessary when the existing ``P'' flange is no longer

serviceable. In conclusion, this AD leaves it to the discretion of the

operator the choice of option and provides all three options as

approved type designs.

One commenter states that the containment shields are not an

acceptable option, due to the fact that the shields could lead to

corrosion of the TEC inner wall, which could compromise the structural

integrity of the TEC. The FAA does not concur. The FAA has performed a

thorough technical review of the proposed containment shields. As part

of this review, multiple TECs were returned from service and have had

their shields removed with subsequent sectioning of the case wall and

shields for evaluation of corrosion extent. In this review no case

walls were found with corrosion

[[Page 66894]]

that compromised case wall thickness. In addition, no residual material

was found that would suggest entrapment of foreign substances. The

shields themselves also exhibited no corrosion that compromises type

design wall thickness. This commenter states that the current cleaning

and inspection procedures may have the potential for entrapment of

cleaning and inspection solutions between the case wall and containment

shields. The FAA has studied this concern and does not believe this is

a problem. The FAA has determined that the containment shields are

attached with a stitch weld, which will allow for sufficient purging of

potentially corrosive solutions. When the TECs were sectioned in the

evaluation, no residual deposits of cleaning or inspection solutions

were found. However, to assure that corrosion due to potential

entrapment of cleaning or inspection fluids is mitigated, the

manufacturer is developing enhanced inspection and cleaning procedures

in the engine overhaul manual.

One commenter states that they hold two Supplemental Type

Certificates (STCs) that provide for modification of the TEC by the

installation of a thicker containment wall, and requests inclusion of

these STCs as a means of compliance to the AD. The FAA concurs and has

revised this final rule accordingly.

One commenter states that the inclusion of an STC in the AD as an

alternative method of compliance gives the STC holder an unfair

marketing advantage. The commenter requests that their company approved

repair be listed in the text of the AD with the STC. The FAA does not

concur. The AD identifies all known type designs and, as such, the STC

is an FAA-approved type design. The commenter does not hold a design

approval and therefore cannot be listed as a method of compliance to

this AD. The commenter is listed in the PW SB as a source acceptable to

PW for performing the approved repair. Therefore, the FAA would

consider them an acceptable source for repair.

One commenter states that due to variations in incidence rate for

uncontained TEC penetrations by engine model, i.e., JT9D-7, JT9D-7Q,

and JT9D-7R4, that the FAA should adjust the proposed AD to be engine

model specific. The FAA does not concur. The FAA finds that any

variation in incident rate is not a significant enough factor to

warrant providing a model-specific inspection interval.

Since issuance of the NPRM, the FAA has received a report that

certain PW JT9D-7R4 TECs were modified improperly. These TECs have a

soft material condition, which renders them incapable of properly

containing debris, as required by this AD. These TECs were modified to

incorporate a replacement ``P'' flange and case wall in accordance with

PW SB No. JT9D-7R4-72-513, Revision 3, November 13, 1996, or prior

revisions. This final rule AD adds a paragraph to the compliance

section requiring heat treatment of all TECs modified in accordance

with PW SB No. JT9D-7R4-72-513, Revision 3, November 13, 1996, or prior

revisions, in accordance with PW SB No. JT9D-7R4-72-534, dated October

18, 1996.

In addition, PW has issued SB No. 6157, Revision 1, dated July 17,

1996, which only differs from the original by adding additional repair

stations. This final rule AD references Revision 1 of this SB.

After careful review of the available data, including the comments

noted above, the FAA has determined that air safety and the public

interest require the adoption of the rule with the changes described

previously. The FAA has determined that these changes will neither

increase the economic burden on any operator nor increase the scope of

the AD.

There are approximately 2,748 engines of the affected design in the

worldwide fleet. The FAA estimates that 740 engines installed on

aircraft of U.S. registry will be affected by this AD, that it will

take approximately 14 work hours per engine to accomplish the required

actions, and that the average labor rate is $60 per work hour. Required

parts will cost approximately $1,404 per engine. Based on these

figures, the total cost impact of the AD on U.S. operators is estimated

to be $1,660,560.

The regulations adopted herein will not have substantial direct

effects on the States, on the relationship between the national

government and the States, or on the distribution of power and

responsibilities among the various levels of government. Therefore, in

accordance with Executive Order 12612, it is determined that this final

rule does not have sufficient federalism implications to warrant the

preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is

not a ``significant regulatory action'' under Executive Order 12866;

(2) is not a ``significant rule'' under DOT Regulatory Policies and

Procedures (44 FR 11034, February 26, 1979); and (3) will not have a

significant economic impact, positive or negative, on a substantial

number of small entities under the criteria of the Regulatory

Flexibility Act. A final evaluation has been prepared for this action

and it is contained in the Rules Docket. A copy of it may be obtained

from the Rules Docket at the location provided under the caption

ADDRESSES.

List of Subjects in 14 CFR Part 39

Air Transportation, Aircraft, Aviation safety, Incorporation by

reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration amends part 39 of

the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 USC 106(g), 40113, 44701.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

96-25-10 Pratt & Whitney: Amendment 39-9853. Docket 95-ANE-57.

Applicability: Pratt & Whitney (PW) JT9D-3, -7, -20, -59A, -70A,

-7Q, and -7R4 series turbofan engines, installed on but not limited

to Airbus A300 and A310 series; Boeing 747 and 767 series; and

McDonnell Douglas DC-10 series aircraft.

Note 1: This airworthiness directive (AD) applies to each engine

identified in the preceding applicability provision, regardless of

whether it has been modified, altered, or repaired in the area

subject to the requirements of this AD. For engines that have been

modified, altered, or repaired so that the performance of the

requirements of this AD is affected, the owner/operator must request

approval for an alternative method of compliance in accordance with

paragraph (b) of this AD. The request should include an assessment

of the effect of the modification, alteration, or repair on the

unsafe condition addressed by this AD; and, if the unsafe condition

has not been eliminated, the request should include specific

proposed actions to address it.

Compliance: Required as indicated, unless accomplished

previously.

To prevent release of uncontained debris from the turbine

exhaust case (TEC) following an internal engine failure, which can

result in damage to the aircraft, accomplish the following:

(a) At the next removal of the TEC from the low pressure turbine

case ``P'' flange for overhaul, where the No. 4 bearing, carbon

seals, lubrication pressurization lines, or scavenge lines are

removed for maintenance after the effective date of this AD, but not

later than 48 months after the effective date of this AD, accomplish

the following:

[[Page 66895]]

(1) For PW JT9D-3A, -7, -7A, -7AH, -7H, -7F, -7J, -20, and -20J

series turbofan engines, accomplish any one of the following

actions:

(i) Install a thicker-walled TEC, with Part Numbers (P/N's)

listed in PW SB No. 6113, dated April 13, 1993, as applicable; or

(ii) Install a modified TEC that incorporates a containment

shield, with P/N's listed in PW SB No. 5907, dated March 27, 1990,

as applicable; or

(iii) Install a modified TEC that incorporates a replacement

``P'' flange and case wall, with P/N's listed in PW SB No. 6118,

Revision 3, dated January 10, 1996, or

(iv) Install a modified TEC that incorporates a replacement

``P'' flange and case wall, with Chromalloy Supplemental Type

Certificate (STC) SE00047AT-D, dated October 15, 1996.

(2) For PW JT9D-7Q and -7Q3 series turbofan engines, accomplish

any one of the following actions:

(i) Install a thicker-walled TEC, with P/N's listed in PW SB No.

5977, dated December 14, 1990; or

(ii) Install a modified TEC that incorporates a containment

shield, with P/N's listed in PW SB No. 5907, dated March 27, 1990,

as applicable; or

(iii) Install a modified TEC that incorporates a replacement

``P'' flange and case wall, with P/N's listed in PW SB No. 6157,

Revision 1, dated July 17, 1996; or

(iv) Install a modified TEC that incorporates a replacement

``P'' flange and case wall, with Chromalloy STC SE00047AT-D, dated

October 15, 1996.

(3) For PW JT9D-59A and -70A series turbofan engines, accomplish

one of the following actions:

(i) Install a thicker-walled TEC, with P/N's listed in PW SB No.

6243, dated February 1, 1996; or

(ii) Install a modified TEC that incorporates a containment

shield, with P/N's listed in PW SB No. 5907, dated March 27, 1990,

as applicable;

(iii) Install a modified TEC that incorporates a replacement

``P'' flange and case wall, with P/N's listed in PW SB No. 6157,

Revision 1, dated July 17, 1996; or

(iv) Install a modified TEC that incorporates a replacement

``P'' flange and case wall, with Chromalloy STC SE00047AT-D, dated

October 15, 1996.

(4) For PW JT9D-7R4D (BG-700 series) turbofan engines,

accomplish one of the following actions:

(i) Install a thicker-walled TEC, with P/N's listed in PW SB No.

JT9D-7R4-72-479, Revision 1, dated November 12, 1993; or

(ii) Install a modified TEC that incorporates a containment

shield, with P/N's listed in PW SB No. JT9D-7R4-72-407, Revision 1,

dated August 16, 1990, as applicable; or

(iii) Install a modified TEC that incorporates a replacement

``P'' flange and case wall, with Chromalloy STC SE00047AT-D, dated

October 15, 1996.

(5) For PW JT9D-7R4D (BG-800 series), -7R4D (BG-900 series), -

7R4D1 (AI-500 series), -7R4E (BG-800 series), -7R4E (BG-900 series),

-7R4E1 (AI-500 series), -7R4E1 (AI-600 series), -7R4E4 (BG-900

series), -7R4G2 (BG-300 series), and -7R4H1 (AI-600 series) turbofan

engines, accomplish any one of the following actions:

(i) Install a thicker-walled TEC, with P/N's listed in PW SB No.

JT9D-7R4-72-534, dated October 18, 1996; or

(ii) Install a modified TEC that incorporates a containment

shield, with P/N's listed in PW SB No. JT9D-7R4-72-466, Revision 2,

dated May 10, 1996; or

(iii) Install a modified TEC that incorporates a replacement

``P'' flange and case wall, with P/N's listed in PW SB No. JT9D-7R4-

72-534, dated October 18, 1996; or

(iv) Install a modified TEC that incorporates a replacement

``P'' flange and case wall, with Chromalloy STC SE00054AT-D, dated

October 19, 1994.

(6) For PW JT9D-7R4D (BG-800 series), -7R4D (BG-900 series), -

7R4D1 (AI-500 series), -7R4E (BG-800 series), -7R4E (BG-900 series),

-7R4E1 (AI-500 series), -7R4E1 (AI-600 series), -7R4E4 (BG-900

series), -7R4G2 (BG-300 series), and -7R4H1 (AI-600 series) turbofan

engines, with TECs that have been modified to incorporate a

replacement flange and case wall, in accordance with PW SB No. JT9D-

7R4-72-513, Revision 3, dated November 13, 1996, or previous

revisions, perform heat treatment of the TECs in accordance with the

Accomplishment Instructions of PW SB No. JT9D-7R4-72-534, dated

October 18, 1996.

(b) An alternative method of compliance or adjustment of the

compliance time that provides an acceptable level of safety may be

used if approved by the Manager, Engine Certification Office. The

request should be forwarded through an appropriate FAA Principal

Maintenance Inspector, who may add comments and then send it to the

Manager, Engine Certification Office.

Note 2: Information concerning the existence of approved

alternative methods of compliance with this airworthiness directive,

if any, may be obtained from the Engine Certification Office.

(c) Special flight permits may be issued in accordance with

sections 21.197 and 21.199 of the Federal Aviation Regulations (14

CFR 21.197 and 21.199) to operate the aircraft to a location where

the requirements of this AD can be accomplished.

(d) The actions required by this AD shall be done in accordance

with the following PW SBs:

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Document No. Pages Revision Date

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SB No. 6113...................... 1-38 Original................ April 13, 1993.

Total pages: 38.

SB No. 5977...................... 1-6 Original................ December 14, 1990.

Total pages: 6.

SB No. JT9D-7R4-72-479........... 1 1....................... November 12, 1993.

2, 3 Original................ February 25, 1993.

4-6 1....................... November 12, 1993.

Total pages: 6.

SB No. 6243...................... 1-6 Original................ February 1, 1996.

Total pages: 6.

SB No. JT9D-7R4-72-513........... 1-19 3....................... November 13, 1996.

Total pages: 19.

SB No. JT9D-7R4-72-534........... 1-26 5 Original................ October 18, 1996.

Total pages: 26.

SB No. 5907...................... 1-32 Original................ March 27, 1990.

Total pages: 32.

SB No. JT9D-7R4-72-407........... 1 1....................... August, 16, 1990.

2-5 Original................ March 30, 1990.

6 1....................... August 16, 1990.

7-22 Original................ March 30, 1990.

Total pages: 22.

SB No. JT9D-7R4-72-466........... 1, 2 2....................... May 10, 1996.

3-8 Original................ January 15, 1993.

9-11 1....................... March 4, 1994.

12, 13 Original................ January 15, 1993.

14-16 1....................... March 4, 1994.

17, 18 Original................ January 15, 1993.

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Total pages: 18.

SB No. 6118...................... 1 3....................... January 10, 1996.

2-5 2....................... April 18, 1995.

6-32 Original................ April 15, 1993.

33 2....................... April 18, 1995.

34-38 Original................ April 15, 1993.

39 1....................... May 20, 1993.

40 Original................ April 15, 1993.

41-44 1....................... May 20, 1993.

45 3....................... January 10, 1996.

Total pages: 45.

SB No. 6157...................... 1 1....................... July 17, 1996.

2-15 Original................ February 9, 1994.

16 1....................... July 17, 1996.

Total pages: 16.

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This incorporation by reference was approved by the Director of

the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR

part 51. Copies may be obtained from Pratt & Whitney, Publications

Department, Supervisor Technical Publications Distribution, M/S 132-

30, 400 Main St., East Hartford, CT 06108; telephone (860) 565-7700,

fax (860) 565-4503. Copies may be inspected at the FAA, New England

Region, Office of the Assistant Chief Counsel, 12 New England

Executive Park, Burlington, MA; or at the Office of the Federal

Register, 800 North Capitol Street NW., suite 700, Washington, DC.

(e) This amendment becomes effective on February 18, 1997.

Issued in Burlington, Massachusetts, on December 4, 1996.

James C. Jones,

Acting Manager, Engine and Propeller Directorate, Aircraft

Certification Service.

[FR Doc. 96-31947 Filed 12-18-96; 8:45 am]

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