Airworthiness Directives; Pratt & Whitney JT9D-7R4 Series Turbofan Engines

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 91-ANE-47; Amendment 39-8878; AD 94-08-06]

Airworthiness Directives; Pratt & Whitney JT9D-7R4 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 JT9D-7R4 series turbofan engines, that

requires initial and repetitive fan blade leading edge inspections, and

either installation of fan blade sets with modified fan blade shrouds

or rework of the fan blade shrouds as a terminating action to the

inspections. This amendment is prompted by reports of flutter-induced

fan blade fractures. The actions specified by this AD are intended to

prevent fan blade fracture and uncontained engine failure, resulting in

possible damage to the aircraft.

DATES: Effective July 5, 1994.

The incorporation by reference of certain publications listed in

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

of July 5, 1994.

ADDRESSES: The service information referenced in this AD may be

obtained from Pratt & Whitney, 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: John Fisher, Aerospace Engineer,

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

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

238-7149, fax (617) 238-7199.

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

Aviation Regulations to include an airworthiness directive (AD) that is

applicable to Pratt & Whitney (PW) JT9D-7R4 series turbofan engines was

published in the Federal Register on June 2, 1993 (58 FR 31356). That

action proposed to require initial and repetitive on-wing or shop fan

blade leading edge inspections to check for leading edge damage in

accordance with PW Service Bulletin (SB) No. 72-255, Revision 5, dated

January 8, 1990; and to require fan blade set replacement or optional

rework of the fan blade shrouds in accordance with PW SB No. 72-309,

Revision 9, dated June 12, 1991. Though the NPRM referenced PW SB No.

72-309, Revision 9, dated June 12, 1991, this final rule incorporates

the later Revision 10, dated September 2, 1993, which is substantially

unchanged from Revision 9. Rework of the fan blade shrouds in

accordance with PW SB No. 72-309, Revision 9, dated June 12, 1991, is

an acceptable alternate means of compliance for paragraphs (c) and (d)

of this AD.

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 comment states that the proposed 90-day requirement for

initializing the inspection program poses a significant hardship and

economic impact due to difficulty in scheduling engine maintenance.

This comment requests extending the initializing period to 180 days.

The Federal Aviation Administration (FAA) agrees that the proposed

initial 90-day eddy current inspection requirement may be burdensome to

some operators. The FAA has therefore added a visual inspection as an

option to the eddy current inspection in this final rule. This visual

inspection offers greater flexibility in scheduling as it can easily be

performed in the field. The FAA does not concur, however, in extending

the initializing period to 180 days, as this time period does not offer

an adequate level of safety based on risk analysis results. This final

rule establishes an interval of 200 cycles in service (CIS) before

visual or eddy current inspection that should enable operators to

initialize the inspection program with minimum disruption to scheduling

without reducing flight safety. Also, the FAA has added guidance

emphasizing the manner in which the visual inspection should be

performed.

One comment requests eliminating the reference in paragraphs (a)

and (b) of the proposed rule to the leading edge refurbishment

described in PW Service Bulletin (SB) No. 72-117, as the determining

factor for beginning the inspection program. The comment further states

that a previous AD, 90-14-08, already requires the leading edge

refurbishment described in PW SB No. 72-117, and therefore meets the

intent of paragraphs (a) and (b) of the proposed rule. The FAA concurs.

Repetitive leading edge refurbishment as described in PW SB No. 72-117

is already required by AD 90-14-08. The compliance section of this AD

has been changed from the wording in the NPRM to eliminate reference to

leading edge refurbishment, and combines paragraphs (a) and (b) of the

proposed rule into a new paragraph (a) which has the same inspection

requirements and interval of 200 CIS as the repetitive inspections of

paragraph (c) of the proposed rule.

One comment states that the mandatory incorporation of the fan

blade shroud angle rework to 52 degrees as described in PW SB No. 72-

309 should be relaxed from within two years after the effective date of

this AD to the next engine shop visit, thereby reducing the potential

for on-wing maintenance induced error. The FAA does not concur. The FAA

has determined that it is necessary to expeditiously remove fan blades

with the 62 degree shroud configuration, thereby reducing the potential

for operating the fan blade in flutter. The FAA has reviewed a risk

analysis study that indicates that a two-year time period for

incorporating this modification is required to lower the risk

sufficiently to avert future potential uncontained fan blade failures.

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 730 PW JT9D-7R4 series engines of the

affected design in the worldwide fleet. The FAA estimates that 220

engines installed on aircraft of U.S. registry would be affected by

this AD, and that the average labor rate is $55 per work hour. The

inspections required by this AD will take approximately 1.6 work hours

per engine. The blade rework will cost approximately $15,600 per

engine. Based on these figures, the total cost impact of the AD on U.S.

operators is estimated to be $3,451,360.

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 14 CFR part

39 of the Federal Aviation Regulations 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:

94-08-06 Pratt & Whitney: Amendment 39-8878. Docket 91-ANE-47.

Applicability: Pratt & Whitney (PW) JT9D-7R4 series turbofan

engines installed on but not limited to Boeing Models 747 and 767

aircraft, and Airbus Models A300 and A310 aircraft.

Compliance: Required as indicated, unless accomplished

previously.

To prevent fan blade fracture and uncontained engine failure,

resulting in possible damage to the aircraft, accomplish the

following:

(a) Perform an initial visual or eddy current inspection of the

fan blade set leading edges for leading edge damage within 200

cycles in service (CIS) after the effective date of this AD, and

rework or replace fan blades as necessary, in accordance with the

Accomplishment Instructions of PW Service Bulletin (SB) No. 72-255,

Revision 5, dated January 8, 1990. Perform the fan blade leading

edge visual inspections using a strong white light, as well as

fingernails and fingertips when inspecting for nicked, eroded, or

blunt leading edges.

(b) Thereafter, perform repetitive visual or eddy current fan

blade leading edge inspections, at intervals not to exceed 200 CIS,

and rework or replace fan blades as necessary, in accordance with

the Accomplishment Instructions of PW SB No. 72-255, Revision 5,

dated January 8, 1990. Perform the fan blade leading edge visual

inspections using a strong white light, as well as fingernails and

fingertips when inspecting for nicked, eroded, or blunt leading

edges.

(c) For PW Model JT9D-7R4H1 engines, install a new or reworked

fan blade set with a 52 degree shroud angle, in accordance with PW

SB No. 72-309, Revision 10, dated September 2, 1993, within 1 year

after the effective date of this AD.

(d) For PW Models JT9D-7R4D, D1, E, E1, G2, and E4 engines,

install a new or reworked fan blade set with a 52 degree shroud

angle, in accordance with PW SB No. 72-309, Revision 10, dated

September 2, 1993, within 2 years after the effective date of this

AD.

(e) Installation of a new or reworked fan blade set with a 52

degree fan blade shroud angle, in accordance with paragraphs (c) or

(d) of this AD, constitutes a terminating action to the inspection

requirements of paragraphs (a) and (b) of 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 Certification Office.

(g) Special flight permits may be issued in accordance with 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 modification and inspections 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. 72-255.......................................... 1-2 5 Jan. 8, 1990.

3-4 4 Aug. 25, 1988.

5 5 Jan. 8, 1990.

6-8 3 Aug. 17, 1987.

Total Pages: 8.

PW SB No. 72-309.......................................... 1 10 Sept. 2, 1993.

2 8 Apr. 5, 1989.

3-4 9 Jun. 12, 1991.

5 (\1\) Oct. 2, 1986.

6 1 Nov. 7, 1986.

7 5 Jul. 22, 1987.

8-10 8 Apr. 5, 1989.

11 10 Sept. 2, 1993

12-18 8 Apr. 5, 1989

19-20 10 Sept. 2, 1993

21 8 Apr. 5, 1989

Total Pages: 21.

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\1\Original.

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, 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 July 5, 1994.

Issued in Burlington, Massachusetts, on April 5, 1994.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification

Service.

[FR Doc. 94-10394 Filed 5-4-94; 8:45 am]

BILLING CODE 4910-13-P