[Federal Register Volume 64, Number 185 (Friday, September 24, 1999)]
[Rules and Regulations]
[Pages 51683-51684]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-24786]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NE-06-AD; Amendment 39-11334; AD 99-20-04]
RIN 2120-AA64


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 an initial and repetitive inspections of certain High Pressure 
Turbine (HPT) stage 1 and stage 2 disks utilizing an improved 
ultrasonic inspection method performed at an approved facility when the 
disks are exposed during a shop visit, and if a crack indicating a 
subsurface anomaly is found, removal from service and replacement with 
a serviceable part. This amendment is prompted by the results of a 
stage 1 HPT disk fracture investigation which has identified a 
population of HPT stage 1 and 2 disks that may have subsurface 
anomalies formed during the forging process. The actions specified by 
this AD are intended to prevent an HPC disk fracture, which could 
result in an uncontained engine failure, damage to the airplane, and an 
in-flight engine shutdown.

DATES: Effective date October 29, 1999. The incorporation by reference 
of certain publications listed in the regulations is approved by the 
Director of the Federal Register as of October 29, 1999.

ADDRESSES: The service information referenced in this AD may be 
obtained from Pratt & Whitney, 400 Main St., East Hartford, CT 06108; 
telephone (860) 565-8770, fax (860) 565-4503. This information may be 
examined at the Federal Aviation Administration (FAA), New England 
Region, Office of the Regional 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: Peter White, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone (781) 
238-7128, fax (781) 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-7R4 
series turbofan engines was published in the Federal Register on June 
4, 1999 (64 FR 29965). That action proposed to require initial and 
repetitive inspections of certain stage 1 and stage 2 high pressure 
turbine (HPT) disks using an improved ultrasonic method whenever the 
disk is exposed during a shop visit. The inspection must be performed 
at an approved facility listed in PW Service Bulletin (SB) JT9D-7R4-72-
553, Revision 1, dated February 17, 1999. If a crack indicating a 
subsurface anomaly is found, the disk must be removed from service and 
replaced with a serviceable part.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comment received.

Request To Shorten the Inspection Intervals

    One commenter requests that the initial and repetitive inspection 
intervals be shortened to six to nine months. The commenter maintains 
that the proposed interval for inspections (exposure during a shop 
visit) could permit flawed disks to remain on an airplane for a year or 
more before detection. The FAA does not agree. The compliance interval 
selected yields an extremely low risk level. The corrected risk is 
extremely low and a small fraction of the risk allowed by FAA 
guidelines. Shortening the compliance interval to the recommended level 
will place an unnecessary burden on the airline industry with little 
impact on fleet safety. The FAA feels that the current compliance plan 
is sufficient to maintain flight safety.
    The AD was edited to clarify the shipping requirements discussed in 
the financial assessment in the compliance section. Due to the 
complexity of the ultrasonic inspection, the compliance plan requires 
that the disks be inspected at an approved facility to ensure that the 
inspections meet the intent. As the inspection requires using a complex 
process and unique equipment, the AD requires that only approved 
facilities perform the inspection. This is not a change from the 
original proposed rule, but paragraph (a) of the compliance section has 
been edited to make this requirement more clear.
    In addition, to simplify the AD, the definition of HPT disk piece 
part accessibility of paragraph (c) was deleted and incorporated into 
paragraph (a).

Conclusion

    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 as proposed. The FAA has 
determined that these changes will neither increase the economic burden 
on any operator nor increase the scope of the AD.

Cost Impact

    There are approximately 131 Pratt & Whitney JT9D-7R4 series 
turbofan engines of the affected design in the worldwide fleet. The FAA 
estimates that 25 engines installed on airplanes of U.S. registry will 
be affected by this AD. The FAA estimates that the shipping cost per 
disk to the facility which will inspect the disk and its return will be 
approximately $250 per disk, that no engines will require an unplanned 
HPT module disassembly/assembly, that the inspection would take 
approximately 8 work hours per disk to accomplish the proposed actions, 
and that the average labor rate is $60 per work hour. Some disks will 
require multiple inspections during their service life. Based on these 
figures, the total cost impact of the proposed AD on U.S. operators is 
estimated to be $88,000. The manufacturer has advised the FAA that the 
all costs relative to the inspection may be reimbursed to the operator.

Regulatory Impact

    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

[[Page 51684]]

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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

99-20-04:   Amendment 39-11334; Docket 99-NE-06-AD.

    Applicability: Pratt & Whitney JT9D-7R4 series turbofan engines, 
installed on but not limited to Boeing 747, Airbus A300 and Airbus 
A310 series airplanes.

    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 (d) 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 a high pressure compressor (HPC) disk 
fracture, which could result in an uncontained engine failure, 
damage to the airplane, and an in-flight engine shutdown, accomplish 
the following:
    (a) For engines with a HPT stage 1 or stage 2 disk installed 
that has a serial number listed in the Accomplishment Instructions 
section of PW Service Bulletin (SB) JT9D-7R4-72-553, Revision 1, 
dated February 17, 1999, perform initial and repetitive ultrasonic 
inspections in accordance with PW SB JT9D-7R4-72-552, Revision 1, 
dated February 17, 1999 at each separation of the HPT disk from the 
HPT module after the effective date of this AD. The disk must be 
sent to an approved facility listed in the Vendor Services or 
Special Components/Materials section of PW SB JT9D-7R4-72-553, dated 
February 17, 1999, for ultrasonic inspection.
    (b) Remove from service those HPT disks found with a crack 
indicating a subsurface anomaly and replace with a serviceable part.
    (c) For engines that do not have a HPT stage 1 or Stage 2 disk 
installed that has a serial number listed in the Accomplishment 
Instructions section of PW SB JT9D-7R4-72-553, Revision 1, dated 
February 17, 1999, no inspections are required.

Alternate Method of Compliance

    (d) 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. 
Operators shall submit their requests 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.

Special Flight Permits

    (e) Special flight permits may be issued in accordance with 
Sec. Sec. 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.

Incorporation by Reference

    (f) The inspection shall be done in accordance with of PW SB 
JT9D-7R4-72-553, Revision 1, dated February 17, 1999. 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 St., East 
Hartford, CT 06108; telephone (860) 565-8770, fax (860) 565-4503. 
Copies may be inspected at the FAA, New England Region, Office of 
the Regional 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.
    (g) This amendment becomes effective on October 29, 1999.

    Issued in Burlington, Massachusetts, on September 16, 1999.
Donald E. Plouffe,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 99-24786 Filed 9-23-99; 8:45 am]
BILLING CODE 4910-13-U