[Federal Register Volume 59, Number 223 (Monday, November 21, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-28634]
[[Page Unknown]]
[Federal Register: November 21, 1994]
VOL. 59, NO. 223
Monday, November 21, 1994
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-ANE-21]
Airworthiness Directives; Pratt & Whitney JT8D Series Turbofan
Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: This document proposes the supersedure of an existing
airworthiness directive (AD), applicable to certain Pratt & Whitney
(PW) JT8D series turbofan engines, that currently requires initial and
repetitive inspections of certain front compressor fan hubs and
shotpeening of the forward and aft rim to web radius. This action would
reduce the initial inspection interval for front compressor fan hubs
installed in all positions of all applicable aircraft, establish a
compliance end-date, and clarify the wording of the compliance
requirements. This proposal is prompted by a report of a front
compressor fan hub fracture installed in a Boeing 737 aircraft that
resulted in the release of fan blades and portions of the hub outer
rim. The actions specified by the proposed AD are intended to prevent
fracture of the front compressor fan hub, which can result in an
uncontained engine failure and damage to the aircraft.
DATES: Comments must be received by January 20, 1995.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), New England Region, Office of the Assistant Chief
Counsel, Attention: Rules Docket No. 94-ANE-21, 12 New England
Executive Park, Burlington, MA 01803-5299. Comments may be inspected at
this location between 8:00 a.m. and 4:30 p.m., Monday through Friday,
except Federal holidays.
The service information referenced in the proposed rule may be
obtained from Pratt & Whitney, Technical Publications Department, M/S
132-30, 400 Main Street, East Hartford, CT 06108. This information may
be examined at the FAA, New England Region, Office of the Assistant
Chief Counsel, 12 New England Executive Park, Burlington, MA.
FOR FURTHER INFORMATION CONTACT: Mark A. Rumizen, Aerospace Engineer,
Engine Certification Office, FAA, Engine and Propeller Directorate, 12
New England Executive Park, Burlington, MA 01803-5299; telephone (617)
238-7137, fax (617) 238-7199.
SUPPLEMENTARY INFORMATION:
Comments Invited
Interested persons are invited to participate in the making of the
proposed rule by submitting such written data, views, or arguments as
they may desire. Communications should identify the Rules Docket number
and be submitted in triplicate to the address specified above. All
communications received on or before the closing date for comments,
specified above, will be considered before taking action on the
proposed rule. The proposals contained in this notice may be changed in
light of the comments received.
Comments are specifically invited on the overall regulatory,
economic, environmental, and energy aspects of the proposed rule. All
comments submitted will be available, both before and after the closing
date for comments, in the Rules Docket for examination by interested
persons. A report summarizing each FAA-public contact concerned with
the substance of this proposal will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this notice must submit a self-addressed,
stamped postcard on which the following statement is made: ``Comments
to Docket Number 94-ANE-21.'' The postcard will be date stamped and
returned to the commenter.
Availability of NPRMs
Any person may obtain a copy of this NPRM by submitting a request
to the FAA, New England Region, Office of the Assistant Chief Counsel,
Attention: Rules Docket No. 94-ANE-21, 12 New England Executive Park,
Burlington, MA 01803-5299.
Discussion
On July 15, 1993, the Federal Aviation Administration (FAA) issued
Airworthiness Directive (AD) 93-14-14, Amendment 39-8638 (58 FR 39644,
July 26, 1993), applicable to Pratt & Whitney (PW) JT8D series turbofan
engines, to require initial and repetitive inspections for cracks, and
removal from service, if necessary, of certain front compressor fan
hubs. Front compressor fan hubs installed on engines in the No. 2
position on Boeing 727 aircraft must be inspected according to a more
aggressive schedule than other installations. In addition, that AD
requires shotpeening of the forward and aft rim to web radius area of
hubs that pass the inspections. That action was prompted by reports of
two front compressor fan hub fractures on engines operating in the No.
2 position on Boeing 727 aircraft. That condition, if not corrected,
could result in a fracture of the front compressor fan hub, which can
result in an uncontained engine failure and damage to the aircraft.
Since the issuance of that AD, the FAA has received a report of a
front compressor fan hub fracture on a PW JT8D engine installed on a
Boeing 737 aircraft. The examination of the failed hardware revealed
the failure mechanism to be identical to that described in AD 93-14-14.
The analysis conducted for that AD concluded that the vibratory stress
environment that caused fan hub fractures was the most severe for
engines installed in the No. 2 position on Boeing 727 aircraft.
Therefore, the FAA addressed this population in a more aggressive
manner than engines installed in other aircraft, or in the No. 1 or No.
3 position on Boeing 727 aircraft. The FAA determined that a similar,
but less severe stress environment existed in engines installed in
other aircraft or positions other than the No. 2 position in the Boeing
727 aircraft, and inspection and shotpeening requirements were
specified for these engines in AD 93-14-14. Since the failure of the
fan hub installed in the Boeing 737 aircraft, the FAA has reassessed
the risk analysis for all installations and determined that the
predicted risk level should be reduced. Therefore, the FAA proposes to
supersede AD 93-14-14 with a reduced initial fan hub inspection
requirement for engines installed in all positions of all applicable
aircraft, by requiring engines removed from the Boeing 727 aircraft No.
2 position to adhere to the Boeing 727 aircraft No. 2 position
inspection requirements, and by establishing a compliance end-date.
The FAA has received comments from operators that the wording of
paragraph (b)(4) of AD 93-14-14 is confusing. The FAA has revised the
wording to emphasize that the repetitive inspection is required at the
next opportunity when the front compressor fan hub is accessible at the
detail level in the shop only after accumulating 2,500 additional
cycles in service (CIS) since the last inspection.
In addition, the FAA has revised the wording in paragraph (d) that
defines a shop visit as an engine removal for engine maintenance that
cannot be performed while installed in the aircraft.
Since publication of AD 93-14-14, PW has issued Alert Service
Bulletin (ASB) No. 6104, Revision 3, dated June 16, 1994, that
describes the reduced initial inspection intervals for the applicable
engine installations.
Since an unsafe condition has been identified that is likely to
exist or develop on other products of this same type design, the
proposed AD would supersede AD 93-14-14 to reduce the initial
inspection interval for front compressor fan hubs installed in all
positions of all applicable aircraft, revise the compliance
requirements for repositioned engines, establish a compliance end-date,
and clarify the wording of the compliance requirements.
The FAA estimates that 1475 engines installed on aircraft of U.S.
registry and 690 domestic uninstalled engines would be affected by this
proposed AD, that it would take approximately 12 work hours per engine
to accomplish the proposed actions, and that the average labor rate is
$55 per work hour. Based on these figures, the total cost impact of the
proposed AD on U.S. operators is estimated to be $1,428,900.
The regulations proposed herein would 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
proposal would not have sufficient federalism implications to warrant
the preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this proposed
regulation (1) is not a ``significant regulatory action'' under
Executive Order 12866; (2) is not a ``significant rule'' under the DOT
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);
and (3) if promulgated, 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 copy of the draft
regulatory evaluation prepared for this action is contained in the
Rules Docket. A copy of it may be obtained by contacting the Rules
Docket at the location provided under the caption ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.
The Proposed Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration proposes to amend
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 removing amendment 39-8638 (58 FR
39644, July 26, 1993) and by adding a new airworthiness directive to
read as follows:
Pratt & Whitney: Docket No. 94-ANE-21. Supersedes AD 93-14-14,
Amendment 39-8638.
Applicability: Pratt & Whitney (PW) Model JT8D-9, -9A, -11, -15,
-15A, -17, -17A, -17R, and -17AR turbofan engines containing front
compressor fan hub Part Number (P/N) 817401 with the following
serial numbers: J78892 through J80538, K32019 through K34018, L32197
through L34133, or M05722 through M07296; and all serial numbers of
fan hubs P/N 594301, 640601, 743301, 749801, 750101, 791801, and
806001. These engines are installed on but not limited to Boeing 727
and 737 series, and McDonnell Douglas DC-9 series aircraft.
Compliance: Required as indicated, unless accomplished
previously.
To prevent fracture of the front compressor fan hub, which can
result in an uncontained engine failure and damage to the aircraft,
accomplish the following:
(a) For front compressor fan hubs installed in engines in the
No. 2 position on Boeing 727 aircraft on or after the effective date
of this airworthiness directive (AD), inspect and shotpeen the front
compressor fan hub in accordance with Appendix A, Appendix B, and
Attachment 1 (NDIP-764) of PW Alert Service Bulletin (ASB) No. 6104,
Revision 3, dated June 16, 1994, as follows:
(1) Initially inspect the front compressor fan hub as follows:
----------------------------------------------------------------------------------------------------------------
Total Part Cycles (TPC) on the
effective date of this AD Initial inspection interval
----------------------------------------------------------------------------------------------------------------
Over 18,001 TPC.................. Inspect at the next shop visit, or within 300 cycles in service (CIS) after
the effective date of this AD, whichever occurs first.
16,501 to 18,000 TPC............. Inspect at the next shop visit, or within 500 CIS after the effective date of
this AD, whichever occurs first.
15,001 to 16,500 TPC............. Inspect at the next shop visit, or within 750 CIS after the effective date of
this AD, whichever occurs first.
13,501 to 15,000 TPC............. Inspect at the next shop visit, or within 1,000 CIS after the effective date
of this AD, whichever occurs first.
10,501 to 13,500 TPC............. Inspect at the next shop visit, or within 1,500 CIS after the effective date
of this AD, whichever occurs first.
Less than 10,501 TPC............. Inspect at the next shop visit but not to exceed 12,000 TPC, or by the
compliance end-date, whichever occurs first.
----------------------------------------------------------------------------------------------------------------
(2) Engines removed from the No. 2 position on Boeing 727
aircraft and reinstalled in aircraft or positions other than the No.
2 position on Boeing 727 aircraft after the effective date of this
AD must adhere to the initial inspection interval specified in
paragraph (a)(1) of this AD. Inspect and shotpeen front compressor
fan hubs on these repositioned engines in accordance with paragraph
(a)(1) of this AD.
(3) Remove front compressor fan hubs from service if cracks are
found during the inspection process and replace with a serviceable
hub.
(4) Shotpeen the front compressor fan hubs that pass the
inspections required by paragraph (a)(1) of this AD, in accordance
with Appendix B of PW ASB No. 6104, Revision 3, dated June 16, 1994,
prior to returning the hub to service.
(5) Thereafter, inspect, shotpeen, and remove from service, if
necessary, front compressor fan hubs that are reinstalled in the No.
2 position of Boeing 727 aircraft, in accordance with Appendix A,
Appendix B, and Attachment 1 (NDIP-764), as applicable, of PW ASB
No. 6104, Revision 3, dated June 16, 1994, as follows:
(i) For hubs that were last inspected and shotpeened with
greater than 12,000 TPC upon inspection, inspect and shotpeen at the
first shop visit after 2,500 CIS since last inspection, but prior to
the accumulation of 8,000 CIS since last inspection.
(ii) For hubs that were last inspected and shotpeened with less
than or equal to 12,000 TPC upon inspection, inspect and shotpeen at
the first shop visit after 2,500 CIS since last inspection, or prior
to accumulating 12,000 TPC, whichever occurs later, but not to
exceed 8,000 CIS since last inspection.
(6) Engines removed from the No. 2 position on Boeing 727
aircraft and reinstalled in aircraft or positions other than the No.
2 position on Boeing 727 aircraft prior to reaching the repetitive
inspection interval specified in paragraph (a)(5) of this AD must be
inspected as follows:
(i) For the next inspection, inspect in accordance with
paragraph (a)(5) of this AD; and
(ii) Thereafter, inspect and shotpeen in accordance with
paragraph (b)(4) of this AD.
(b) For front compressor fan hubs installed in engines that are
installed in aircraft or positions other than the No. 2 position on
Boeing 727 aircraft on the effective date of this AD, inspect and
shotpeen the front compressor fan hubs in accordance with Appendix
A, Appendix B, and Attachment 1 (NDIP-764) of PW ASB No. 6104,
Revision 3, dated June 16, 1994, as follows:
(1) Initially inspect the front compressor fan hub at the next
shop visit after the effective date of this AD, but not later than
the compliance end-date.
(2) Remove front compressor fan hubs from service if cracks are
found during the inspection process and replace with a serviceable
hub.
(3) Shotpeen the front compressor fan hubs that pass the
inspection requirements specified in paragraph (b)(1) of this AD, in
accordance with Appendix B of PW ASB No. 6104, Revision 3, dated
June 16, 1994, prior to returning the hub to service.
(4) Thereafter, upon accumulating 2,500 addition CIS since the
last inspection, inspect, shotpeen, and remove from service, if
necessary, front compressor fan hubs that are not reinstalled in the
No. 2 position on Boeing 727 aircraft, in accordance with Appendix
A, Appendix B, and Attachment 1 (NDIP-764) of PW ASB No. 6104,
Revision 3, dated June 16, 1994, when the front compressor fan hub
is accessible at the detail level in the shop.
(5) Thereafter, inspect, shotpeen, and remove from service, if
necessary, front compressor fan hubs that are reinstalled in the No.
2 position of Boeing 727 aircraft after the effective date of this
AD in accordance with paragraph (a)(5) of this AD.
(c) Inspect and shotpeen front compressor fan hubs that were
inspected and shotpeened in accordance with Appendix A, Appendix B,
and Attachment 1 (NDIP-764) of PW ASB No. 6104, dated December 21,
1992, PW ASB No. 6104, Revision 1, dated May 21, 1993, or PW ASB No.
6104, Revision 2, dated June 18, 1993, prior to the effective date
of this AD in accordance with paragraphs (a)(5) or (b)(4) of this
AD, as applicable.
(d) For the purpose of this AD, the compliance end-date
referenced in paragraphs (a)(1) and (b)(1) of this AD is defined as
December 31, 1999, or 6,000 TPC after the effective date of this AD,
whichever occurs later.
(e) For the purpose of this AD, a shop visit is defined as an
engine removal for engine maintenance that cannot be performed while
installed in the aircraft, and that entails separation of pairs of
mating (lettered) engine flanges or the removal of a compressor
disk, hub, or spool, or removal of a turbine disk.
(f) For the purpose of this AD, accessibility of a front
compressor fan hub at the detail level in the shop is defined as
engine maintenance that entails separation of the front compressor
fan hub from the front compressor and removal of the fan blades.
(g) Report the front compressor fan hub part number, total time,
and total cycles in service for each hub that passes the inspections
defined in this AD, within 60 days after the inspection, to the
Manager, Engine Certification Office, Engine and Propeller
Directorate, Aircraft Certification Service, FAA, 12 New England
Executive Park, Burlington, Massachusetts, 01803-5299; fax (617)
238-7199. For any hub that is found cracked, submit the information
requested in paragraph B of Part 4, of the Accomplishment
Instructions of PW ASB No. 6104, Revision 3, dated June 16, 1994,
within 60 days after the inspection to the Manager, Engine
Certification Office, at the address identified above. The reporting
requirements of this AD terminate one year after the effective date
of this AD. Information collection requirements contained in this
regulation have been approved by the Office of Management and Budget
(OMB) under the provision of the Paperwork Reduction Act of 1980 (44
U.S.C. 3501-3520) and have been assigned OMB Control Number 2120-
0056.
(h) 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.
(i) Special flight permits may be issued in accordance with
Secs. 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.
Issued in Burlington, Massachusetts, on November 14, 1994.
James C. Jones,
Acting Manager, Engine and Propeller Directorate, Aircraft
Certification Service.
[FR Doc. 94-28634 Filed 11-18-94; 8:45 am]
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