[Federal Register Volume 59, Number 249 (Thursday, December 29, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-31870]
[[Page Unknown]]
[Federal Register: December 29, 1994]
=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-ANE-54; Amendment 39-9102; AD 94-26-06]
Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan
Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule; request for comments.
-----------------------------------------------------------------------
SUMMARY: This amendment adopts a new airworthiness directive (AD) that
is applicable to Pratt & Whitney (PW) JT9D series turbofan engines.
This action requires initial and repetitive in-shop or on-wing
inspections of the diffuser case rear rail for cracking, and removal,
if necessary, of the diffuser case. This amendment is prompted by
multiple reports of diffuser case rear rail cracking and two reports of
diffuser case rupture. The actions specified in this AD are intended to
prevent diffuser case rupture and an uncontained engine failure.
DATES: Effective January 13, 1995.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of January 13, 1995.
Comments for inclusion in the Rules Docket must be received on or
before February 27, 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-54, 12 New England
Executive Park, Burlington, MA 01803-5299.
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 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: On September 16, 1993, the Federal Aviation
Administration (FAA) issued airworthiness directive (AD) 93-19-02,
Amendment 39-8695 (58 FR 51212, October 1, 1993), applicable to Pratt &
Whitney (PW) JT9D-3A, -7, -7H, -7A, -7AH, -7F, -7J, -20, and -20J
turbofan engines. That AD requires eddy current inspection and
modification of the diffuser case rear rail, and ultrasonic,
metallographic, and X-ray inspections of specific locations in the
diffuser case. That action was prompted by reports of 2 additional
diffuser case failures that occurred within significantly shorter time
intervals since last inspection than that specified in a previous AD.
That condition, if not corrected, could result in diffuser case rupture
and an uncontained engine failure.
On September 22, 1994, the FAA issued Revision 1 to AD 93-19-02,
Amendment 39-9038 (59 FR 49789, September 30, 1994) to correct an error
in paragraph numbering in the compliance section and allow modification
of diffuser cases in accordance with previous revisions of PW Service
Bulletin No. 5805 as an alternative means of compliance to paragraph
(o) of that AD.
The FAA has determined that the diffuser case on PW JT9D-59A, -70A,
-7Q, and -7Q3 series turbofan engines may also develop cracks in the
rear rail. The diffuser case rear rail is a structural hat section and
stiffens the casing shell under conditions of high pressure and
temperature. The rear rail has developed a cracking problem in service
due to high stresses located adjacent to the strut bosses. These cracks
initiate and propagate in low cycle fatigue (LCF) until the critical
crack length is exceeded. At this point, the cracking mode may change
to rapid tensile, and a rupture may occur.
In an effort to better understand the diffuser case failure mode, a
rig test was performed. This test examined crack initiation and growth
rates in weld-repaired versus non-weld-repaired diffuser cases. Results
of the test established that cracks initiate and propagate more rapidly
in weld-repaired diffuser cases.
In addition, the testing revealed that diffuser case rear rails
that have been modified in accordance with PW Service Bulletin (SB) No.
5768 and SB No. 5654 experience lower rates of crack initiation. Pratt
& Whitney SB 5768 and SB 5654 both provide enhancements to the LCF
characteristics and life of the diffuser case rear rail by removing
electrochemically machined areas on the rear rail, and removing stress
concentrations caused by sharp edges on the rear rail. Incorporation of
PW SB 5768 and SB 5654 provides relaxed intervals for inspection of the
diffuser case rear rail as defined in PW SB No. 5749, Revision 4, dated
May 10, 1993.
To date there have been varying degrees of diffuser case rear rail
cracking on the PW JT9D-59A, -70A, -7Q, and -7Q3 diffuser cases. The
FAA has received multiple reports of in-service cracking. Two reported
cracks measured approximately 5 inches in length, and in two incidents
the diffuser case ruptured. The FAA has determined that these two
incidents may have been prevented if the operators had performed the
inspections described in the SB required by this final rule.
The FAA has reviewed and approved the technical contents of PW SB
No. 5749, Revision 4, dated May 10, 1993, that describes procedures for
in-shop eddy current inspections (ECI) or fluorescent penetrant
inspections (FPI), or on-wing ECI, of the diffuser case rear rail for
cracking.
Since an unsafe condition has been identified that is likely to
exist or develop on other engines of the same type design, this AD is
being issued to prevent diffuser case rupture and an uncontained engine
failure. This AD requires initial and repetitive in-shop ECI or FPI, or
on-wing ECI, of the diffuser case rear rail for cracking, and removal
from service of diffuser cases with cracks that exceed 1.5 inches in
length. The actions are required to be accomplished in accordance with
the service bulletin described previously.
Since a situation exists that requires the immediate adoption of
this regulation, it is found that notice and opportunity for prior
public comment hereon are impracticable, and that good cause exists for
making this amendment effective in less than 30 days.
Comments Invited
Although this action is in the form of a final rule that involves
requirements affecting flight safety and, thus, was not preceded by
notice and an opportunity for public comment, comments are invited on
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES!.
All communications received on or before the closing date for comments
will be considered, and this rule may be amended in light of the
comments received. Factual information that supports the commenter's
ideas and suggestions is extremely helpful in evaluating the
effectiveness of the AD action and determining whether additional
rulemaking action would be needed.
Comments are specifically invited on the overall regulatory,
economic, environmental, and energy aspects of the rule that might
suggest a need to modify the 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 that
summarizes each FAA-public contact concerned with the substance of this
AD 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-54.'' The postcard will be date stamped and
returned to the commenter.
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.
The FAA has determined that this regulation is an emergency
regulation that must be issued immediately to correct an unsafe
condition in aircraft, and is not a ``significant regulatory action''
under Executive Order 12866. It has been determined further that this
action involves an emergency regulation under DOT Regulatory Policies
and Procedures (44 FR 11034, February 26, 1979). If it is determined
that this emergency regulation otherwise would be significant under DOT
Regulatory Policies and Procedures, a final regulatory evaluation will
be prepared and placed in the Rules Docket. A copy of it, if filed, 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:
94-26-06 Pratt & Whitney: Amendment 39-9102. Docket 94-ANE-54.
Applicability: Pratt & Whitney (PW) JT9D-59A, -70A, -7Q, and -
7Q3 series turbofan engines, installed on but not limited to Airbus
A300 series, Boeing 747 series, and McDonnell Douglas DC-10 series
aircraft.
Compliance: Required as indicated, unless accomplished
previously.
To prevent diffuser case rupture and an uncontained engine
failure, accomplish the following:
(a) For diffuser cases that have not been inspected in
accordance with PW Service Bulletin (SB) No. 5749, Revision 3, dated
April 25, 1989, or earlier versions of that SB, prior to the
effective date of this AD, accomplish the following:
(1) If maintenance records indicate that a fluorescent penetrant
inspection (FPI) was performed on the entire diffuser case rear rail
and the diffuser case has accumulated less than 475 cycles in
service (CIS) since that FPI, perform an initial on-wing eddy
current inspection (ECI), or in-shop ECI or FPI, of the diffuser
case rear rail for cracking in accordance with PW SB No. 5749,
Revision 4, dated May 10, 1993, within 500 CIS since the last
diffuser case FPI.
(2) If maintenance records indicate that an FPI was performed on
the entire diffuser case rear rail and the diffuser case has
accumulated 475 or more CIS since that FPI, perform an initial on-
wing ECI, or in-shop ECI or FPI, of the diffuser case rear rail for
cracking in accordance with PW SB No. 5749, Revision 4, dated May
10, 1993, within 25 CIS after the effective date of this AD.
(3) If maintenance records are unavailable, or if it is unknown
when the last FPI was performed on the entire diffuser case rear
rail, perform an initial on-wing ECI, or in-shop ECI or FPI, of the
diffuser case rear rail for cracking in accordance with PW SB No.
5749, Revision 4, dated May 10, 1993, within 25 CIS after the
effective date of this AD.
(4) For diffuser cases introduced into service subsequent to the
effective date of this AD, perform an initial on-wing ECI, or in-
shop ECI or FPI, of the diffuser case rear rail for cracking in
accordance with PW SB No. 5749, Revision 4, dated May 10, 1993,
within the cyclic intervals specified in Table 1 of PW SB No. 5749,
Revision 4, dated May 10, 1993.
(b) For diffuser cases that have been inspected in accordance
with PW SB No. 5749, Revision 3, dated April 25, 1989, or earlier
versions of that SB, prior to the effective date of this AD,
accomplish the following:
(1) Perform an initial on-wing ECI, or in-shop ECI or FPI, of
the diffuser case rear rail for cracking in accordance with PW SB
No. 5749, Revision 4, dated May 10, 1993, within the cyclic
intervals specified in Table 1 of PW SB No. 5749, Revision 4, dated
May 10, 1993.
(2) If maintenance records indicate that the diffuser case has
accumulated more CIS since the last on-wing ECI, or in-shop ECI or
FPI, performed in accordance with PW SB No. 5749, Revision 3, dated
April 25, 1989, or earlier versions of that SB, than the cyclic
intervals specified in Table 1 of PW SB No. 5749, Revision 4, dated
May 10, 1993, perform an initial on-wing ECI, or in-shop ECI or FPI,
of the diffuser case rear rail for cracking in accordance with PW SB
No. 5749, Revision 4, dated May 10, 1993, within 25 CIS after the
effective date of this AD.
(c) If no cracks are found in the diffuser case rear rail during
the initial inspections required by paragraph (a) or (b) of this AD,
as applicable, perform subsequent on-wing ECI, or in-shop ECI or
FPI, of the diffuser case rear rail for cracking in accordance with
PW SB No. 5749, Revision 4, dated May 10, 1993, within the cyclic
intervals specified in Table 1 of PW SB No. 5749, Revision 4, dated
May 10, 1993.
(d) If cracks are found in diffuser case rear rails during the
inspections required by paragraph (a), (b), or (c) of this AD, as
applicable, determine the length of the crack:
(1) If the crack is less than 1.5 inches in length, continue in
service and reinspect in accordance with the Accomplishment
Instructions of PW SB No. 5749, Revision 4, dated May 10, 1993, at
intervals not to exceed 75 CIS since the last inspection.
(2) If the crack is 1.5 inches or greater in length, prior to
further flight remove the diffuser case from service for repair and
replace with a serviceable part.
(e) 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.
(f) 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.
(g) The actions required by this AD shall be done in accordance
with the following service document:
------------------------------------------------------------------------
Document No. Pages Revision Date
------------------------------------------------------------------------
PW SB No. 5749..................... 1-13 4 May 10, 1993.
Total pages.................... 13
------------------------------------------------------------------------
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.
(h) This amendment becomes effective on January 13, 1995.
Issued in Burlington, Massachusetts, on December 14, 1994.
Kirk E. Gustafson,
Acting Manager, Engine and Propeller Directorate, Aircraft
Certification Service.
[FR Doc. 94-31870 Filed 12-28-94; 8:45 am]
BILLING CODE 4910-13-P
