[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]


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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.
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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      
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PW SB No. 5749.....................    1-13        4   May 10, 1993.    
    Total pages....................      13                             
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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, 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]
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