Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan Engines

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 92-ANE-23; Amendment 39-8916; AD 94-10-09]

Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan

Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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

applicable to Pratt & Whitney (PW) JT9D series turbofan engines, that

requires initial and repetitive inspections of the sixth stage low

pressure turbine (LPT) inner airseal, and modification of the sixth

stage LPT inner airseal to reduce the potential for two failure modes.

This amendment is prompted by reports of thermal mechanical

interference inducing low cycle fatigue (LCF) cracks at two locations

on the sixth stage LPT inner airseal, resulting in five uncontained

failures. The actions specified by this AD are intended to prevent an

uncontained failure of the sixth stage LPT inner airseal, which can

result in damage to the aircraft.

DATES: Effective September 13, 1994.

The incorporation by reference of certain publications listed in

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

of September 13, 1994.

ADDRESSES: The service information referenced in this AD may be

obtained from Pratt & Whitney, Publication Department, 400 Main Street,

East Hartford, CT 06108. 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 7, 1993

(58 FR 31920). That action proposed to require initial and repetitive

on-wing borescope or eddy current inspections of the sixth stage low

pressure turbine (LPT) inner airseal rear retaining wing, initial and

repetitive on-wing eddy current inspections of the sixth stage LPT

inner airseal knife edges, rework of the sixth stage inner airseal

knife edges, which is a terminating action to the repetitive knife edge

inspections, and rework of the sixth stage LPT inner airseal rear

retaining wing, in accordance with the following service bulletins

(SB's):

PW SB No. 5978, Revision 3, dated May 20, 1992; PW SB No. 5979,

Revision 2, dated April 28, 1992; PW SB No. 5847, Revision 2, dated

October 31, 1990; and PW SB No. 5745, Revision 2, dated October 24,

1990.

Interested persons have been afforded an opportunity to participate

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

the comment received.

The comment requests the inclusion of PW SB No. 6054, Revision 1,

dated April 24, 1992, in the proposed rule. This SB describes

installation of a new 6th stage LPT inner airseal as a terminating

action to the required inspections and rework. The FAA concurs. This

final rule includes the option of installing a new, improved 6th stage

LPT inner airseal, in accordance with PW SB No. 6054, Revision 1, dated

April 24, 1992, as a terminating action to the inspections and rework

required by this AD.

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 602 Pratt & Whitney Model JT9D-59A, -70A, -

7Q, and -7Q3 turbofan engines of the affected design in the worldwide

fleet. The FAA estimates that 121 engines installed on aircraft of U.S.

Registry would be affected by this proposed AD, that it would take

approximately 153 work hours per engine to accomplish the required

actions, and that the average labor rate is $55 per work hour. The FAA

estimates that approximately 50% of affected engines have already

incorporated the knife edge modification described in PW SB No. 5847,

Revision 2, dated October 31, 1990, and that approximately 5% of

affected engines have already incorporated the retaining wing

modification described in PW SB No. 5745, Revision 2, dated October 24,

1990. The average utilization of these engines is 2 cycles per day, and

the program duration is estimated to be 20 years. Based on these

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

estimated to be $981,479 over a 20 year period.

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 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C.

106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

94-10-09 Pratt & Whitney: Amendment 39-8916. Docket 92-ANE-23.

Applicability: Pratt & Whitney (PW) Model JT9D-59A, -70A, -7Q,

and -7Q3 turbofan engines, installed on but not limited to Boeing

747 series, McDonnell Douglas DC-10 series, and Airbus A300 series

aircraft.

Compliance: Required as indicated, unless accomplished

previously.

To prevent an uncontained failure of the sixth stage low

pressure turbine (LPT) inner airseal, which can result in damage to

the aircraft, accomplish the following:

(a) For engines that have not had the sixth stage LPT inner

airseal reworked in accordance with PW Service Bulletin (SB) No.

5847, Revision 2, dated October 31, 1990, eddy current inspect the

sixth stage LPT inner airseal knife edges for cracks in accordance

with the Accomplishment Instructions of PW SB No. 5979, Revision 2,

dated April 28, 1992, and remove cracked sixth stage LPT inner

airseals, as follows:

(1) For sixth stage LPT inner airseals identified by Part Number

(P/N) in PW SB No. 5979, Revision 2, dated April 28, 1992, with

greater than 2,500 cycles since new (CSN) on the effective date of

this AD, accomplish an initial eddy current inspection prior to

accumulating more than 250 cycles in service (CIS) after the

effective date of this AD, or within 1,000 CIS since the last in-

shop fluorescent penetrant inspection, whichever occurs later.

(2) For sixth stage LPT inner airseals listed by P/N in PW SB

No. 5979, Revision 2, dated April 28, 1992, with less than or equal

to 2,500 CSN on the effective date of this AD, accomplish an initial

eddy current inspection prior to accumulating more than 2,750 CSN,

or within 1,000 CIS since the last in-shop fluorescent penetrant

inspection, whichever occurs later.

(3) For sixth stage LPT inner airseals that meet the continue in

service criteria described in PW SB No. 5979, Revision 2, dated

April 28, 1992, thereafter eddy current inspect the sixth stage LPT

inner airseal knife edges for cracks in accordance with the

Accomplishment Instructions of PW SB No. 5979, Revision 2, dated

April 28, 1992, at intervals not to exceed 1,000 CIS since the last

eddy current inspection in accordance with this AD.

(4) Remove cracked sixth stage LPT inner airseals that do not

meet the continue in service criteria described in PW SB No. 5979,

Revision 2, dated April 28, 1992, and replace with a new, or

serviceable sixth stage LPT inner airseal that has been reworked in

accordance with paragraph (b) of this AD.

(b) Rework the sixth stage LPT inner airseal knife edge

diameters in accordance with the Accomplishment Instructions of PW

SB 5847, Revision 2, dated October 31, 1990, at the next shop visit

after the effective date of this AD where the LPT module is

accessible, or not later than January 1, 1996, whichever occurs

first. Accomplishment of this rework constitutes a terminating

action to the initial and repetitive inspection requirements of

paragraph (a)(1), (a)(2), and (a)(3) of this AD.

(c) Eddy current or borescope inspect sixth stage LPT inner

airseal rear retaining wings for cracks in accordance with the

Accomplishment Instructions of PW SB No. 5978, Revision 3, dated May

20, 1992, and remove cracked sixth stage LPT inner airseals, as

follows:

(1) For sixth stage LPT inner airseals identified by P/N in PW

SB No. 5978, Revision 3, dated May 20, 1992, with greater than 500

CSN on the effective date of this AD, accomplish an initial eddy

current or borescope inspection prior to accumulating more than 250

CIS after the effective date of this AD, or 500 CIS since the last

in-shop fluorescent penetrant inspection, whichever occurs later.

(2) For sixth stage LPT inner airseals identified by P/N in PW

SB No. 5978, Revision 3, dated May 20, 1992, with less than or equal

to 500 CSN on the effective date of this AD, accomplish an initial

eddy current or borescope inspection prior to accumulating 750 CSN,

or 500 CIS since the last in-shop fluorescent penetrant inspection,

whichever occurs later.

(3) For sixth stage LPT inner airseals that meet the continue in

service criteria described in PW SB No. 5978, Revision 3, dated May

20, 1992, thereafter eddy current or borescope inspect the sixth

stage LPT inner airseal retaining wing for cracks at intervals

specified in accordance with the Accomplishment Instructions of PW

SB No. 5978, Revision 3, dated May 20, 1992.

(4) Remove cracked sixth stage LPT inner airseals that do not

meet the continue in service criteria described in PW SB No. 5979,

Revision 2, dated April 28, 1992, and replace with a new, or

serviceable sixth stage LPT inner airseal that has been reworked in

accordance with paragraph (b) of this AD.

(b) Rework the sixth stage LPT inner airseal knife edge

diameters in accordance with the Accomplishment Instructions of PW

SB 5847, Revision 2, dated October 31, 1990, at the next shop visit

after the effective date of this AD where the LPT module is

accessible, or not later than January 1, 1996, whichever occurs

first. Accomplishment of this rework constitutes a terminating

action to the initial and repetitive inspection requirements of

paragraph (a)(1), (a)(2), and (a)(3) of this AD.

(c) Eddy current or borescope inspect sixth stage LPT inner

airseal rear retaining wings for cracks in accordance with the

Accomplishment Instructions of PW SB No. 5978, Revision 3, dated May

20, 1992, and remove cracked sixth stage LPT inner airseals, as

follows: (1) For sixth stage LPT inner airseals identified by P/N in

PW SB No. 5978, Revision 3, dated May 20, 1992, with greater than

500 CSN on the effective date of this AD, accomplish an initial eddy

current or borescope inspection prior to accumulating more than 250

CIS after the effective date of this AD, or 500 CIS since the last

in-shop fluorescent penetrant inspection, whichever occurs later.

(2) For sixth stage LPT inner airseals identified by P/N in PW SB

No. 5978, Revision 3, dated May 20, 1992, with less than or equal to

500 CSN on the effective date of this AD, accomplish an initial eddy

current or borescope inspection prior to accumulating 750 CSN, or

500 CIS since the last in-shop fluorescent penetrant inspection,

whichever occurs later. (3) For sixth stage LPT inner airseals that

meet the continue in service criteria described in PW SB No. 5978,

Revision 3, dated May 20, 1992, thereafter, eddy current or

borescope inspect the sixth stage LPT inner airseal retaining wing

for cracks at intervals specified in accordance with the

Accomplishment Instructions of PW SB No. 5978, Revision 3, dated May

20, 1992. (4) Remove cracked sixth stage LPT inner airseals that do

not meet the continue in service criteria described in PW SB No.

5978, Revision 3, dated May 20, 1992, and replace with a new, or

serviceable sixth stage LPT inner airseal that has been reworked in

accordance with paragraph (d) of this AD.

(5) Thereafter, inspect initially, reinspect, and remove from

service, if necessary, the replacement sixth stage LPT inner

airseals in accordance with paragraph (c)(1), (c)(2), (c)(3), and

(c)(4) of this AD.

(d) Rework the sixth stage LPT inner airseal rear retaining wing

in accordance with the Accomplishment Instructions of PW SB 5745,

Revision 2, dated October 24, 1990, at the next shop visit after the

effective date of this AD where the LPT module is accessible, or not

later than January 1, 1996, whichever occurs first.

NOTE: Rework of the sixth stage LPT inner airseal rear retaining

wing in accordance with paragraph (d) of this AD does not exempt

sixth stage LPT inner airseals from initial and repetitive

inspections in accordance with paragraph (c)(1), (c)(2), (c)(3) of

this AD.

(e) Installation of a new, improved 6th stage LPT inner airseal,

in accordance with PW SB No. 6054, Revision 1, dated April 24, 1992,

constitutes terminating action to the inspections and rework

required by this AD.

(f) 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: Information concerning the existence of approved

alternative methods of compliance with this airworthiness directive,

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

(g) 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 airplane to a location where

the requirements of this AD can be accomplished.

(h) The inspections and modifications shall be done in

accordance with the following service bulletins:

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Document No. Pages Revision Date

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PW SB No. 5978.................................. 1 3............... May 20, 1992.

2 Original........ December 19, 1990.

3-4 2............... April 28, 1992.

5-11 1 October 10,

1991..

12 3 October 10,

1991..

13-18 1............... October 10, 1991.

19 3............... May 20, 1991.

20-33 1............... October 10, 1991.

34 2............... April 28, 1992.

Total Pages: 34.

PW SB No. 5979.................................. 1 2............... April 28, 1992.

2 Original........ December 20, 1990.

3-4 1............... September 27, 1991.

5-33 Original........ December 19, 1990.

34 1............... September 27, 1991.

35-36 Original........ December 19, 1990.

37 2............... April 28, 1992.

Total Pages: 37.

PW SB No. 5847 1-4 2 October 31, 1990...........

5 Original........ April 11, 1989.

6 2............... October 31, 1990.

7 Original........ April 11, 1989.

8 2............... October 11, 1989.

9 Original........ April 11, 1989.

10 2............... October 11, 1989.

Total Pages: 10.

PW SB No. 5745.................................. 1-9 2............... October 24, 1990.

Total Pages: 9.

PW SB No. 6054.................................. 1-4 1............... April 24, 1992.

5-7 Original........ November 6, 1991.

8 1............... April 24, 1992.

9-16 Original........ November 6, 1991.

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, Publication

Department, 400 Main Street, East Hartford, CT 06108. 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.

(i) This amendment becomes effective on September 13, 1994.

Issued in Burlington, Massachusetts, on July 7, 1994.

Michael H. Borfitz,

Acting Manager, Engine and Propeller Directorate, Aircraft

Certification Service.

[FR Doc. 94-17068 Filed 7-14-94; 8:45 am]

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