[Federal Register Volume 62, Number 235 (Monday, December 8, 1997)]
[Rules and Regulations]
[Pages 64514-64517]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-31965]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-ANE-04; Amendment 39-10234; AD 97-25-10]
RIN 2120-AA64


Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan 
Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

[[Page 64515]]

SUMMARY: This amendment supersedes an existing airworthiness directive 
(AD), applicable to certain Pratt & Whitney JT9D series turbofan 
engines, that currently requires initial and repetitive eddy current 
inspection (ECI) or fluorescent penetrant inspection (FPI) for cracks 
in first stage high pressure turbine (HPT) disk cooling air holes. This 
amendment requires initial and repetitive FPI for cracks in cooling air 
holes of additional first stage HPT disks, and replacement with 
serviceable parts. In addition, this amendment requires initial and 
repetitive FPI for cracks in tie bolt holes of certain other affected 
second stage HPT disks installed in PW JT9D series turbofan engines. 
This amendment is prompted by reports of a cracked cooling air hole on 
one first stage HPT disk, and a cracked tie bolt hole on one second 
stage HPT disk. The actions specified by this AD are intended to 
prevent turbine disk failure due to cooling air hole or tie bolt hole 
cracking, which could result in an uncontained engine failure and 
damage to the aircraft.

DATES: Effective January 12, 1998.

ADDRESSES: The service information referenced in this AD may be 
obtained from Pratt & Whitney, 400 Main St., East Hartford, CT 06108; 
telephone (860) 565-6600, fax (860) 565-4503. This information may be 
examined at the FAA, New England Region, Office of the Assistant Chief 
Counsel, 12 New England Executive Park, Burlington, MA. 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 01803-5299; or at the Office 
of the Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.

FOR FURTHER INFORMATION CONTACT: Tara Goodman, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone (781) 
238-7130, fax (781) 238-7199.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) by superseding airworthiness 
directive (AD) 91-04-10, Amendment 39-6859 (56 FR 5343, February 11, 
1991), applicable to Pratt & Whitney (PW) JT9D series turbofan engines, 
was published in the Federal Register on March 19, 1997 (62 FR 12979). 
That action proposed to require initial and repetitive fluorescent 
penetrant inspections (FPI) for cracks in cooling air holes of affected 
first stage high pressure turbine (HPT) disks, and, if necessary, 
replacement with serviceable parts. In addition, the action proposed to 
require initial and repetitive FPI for cracks in tie bolt holes of all 
affected second stage HPT disks. Finally, that action proposed to 
require reporting findings of cracked turbine disks.
    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 commenter states that since the root cause of the crack which 
was found on the cooling hole of the improved disk, part number (P/N) 
840301, was caused by improper tooling application (use of reamer 
instead of a carbide insert) at the specified supplier, only the 
suspect supplier and lots should be affected by the AD. The commenter 
maintains that if the FAA suspects PW's qualified carbide insert 
machining process, every maintenance process requiring the 
manufacturer's qualification should always require FAA qualification in 
future. The Federal Aviation Administration (FAA) does not concur. The 
improved disk, P/N 840301, is manufactured with the new reamer tooling 
method; however, a disk of this P/N was found with cooling hole 
cracking. The reamer method was introduced by manufacturers to preclude 
abusive machining that was found using the carbide insert method. 
Investigation has shown that both the carbide insert method and the 
reamer method are subject to the same abusive machining phenomenon. The 
FAA approves manufacturing and maintenance processes, which are updated 
as necessary.
    The same commenter requests that the FAA and PW develop an 
inspection procedure that can detect not only a crack but detect 
whether a severely worked layer of material exists or not, so that 
unnecessary repetitive inspections can be minimized by removing those 
disks. The FAA does not concur. It is not possible to detect 100% of 
the possible cracking conditions in the field using current inspection 
methods. Therefore, repetitive inspections are necessary for disks that 
are in service because cracking can propagate in fatigue from a layer 
of severely worked material resulting from the manufacturing process.
    The same commenter requests the FAA extend the initial inspection 
requirement for disks that have been previously inspected, noting that 
the AD as proposed would allow 1,500 cycles in service (CIS) before 
initial inspection for disks never inspected while only 250 CIS for 
disks that have been inspected but that have accumulated more than 
3,500 CIS since last inspection. The FAA does not concur. The current 
AD, effective in 1991, requires repetitive inspections of disks 
installed in JT9D-59A, -70A, -7Q, and -7Q3 engines at intervals not to 
exceed 3,500 CIS. Therefore, the example cited by the commenter should 
not occur, as disks installed in JT9D-59A or -7Q engines should never 
exceed 3,500 CIS since last inspection. Only if a disk installed in a 
JT9D-7R4 engine had exceeded 3,500 CIS since last inspection would the 
requirement to inspect no later than 250 CIS after the effective date 
of this AD apply. This inspection requirement was considered in the 
risk analysis and the FAA has determined that it is necessary. The 
commenter does not indicate how many JT9D-7R4 engines might be affected 
by the 250 CIS initial inspection requirement. Individual operators can 
apply for an adjustment to that compliance time under paragraph (d) of 
the AD.
    One commenter states that the mandated use of FPI does not provide 
all possible assurance that defective HPT disks will be removed from 
service. The commenter believes that eddy current inspection, or a 
combination of the two methods, would clearly provide a greater 
probability of crack detection. The FAA does not concur. The first 
stage turbine cooling air holes and second stage tie bolt holes have 
low aspect ratios. The FAA has determined that FPI of low aspect ratio 
holes is adequate for detecting cracks in these locations.
    One commenter states that there appears to be anomalies in the 
requirements for disks that have been in service for over 6,000 cycles 
since new (CSN), as stated in paragraph (b)(1)(i) of the compliance 
section. The commenter maintains that as the paragraph reads in the 
proposed rule, this inspection will always occur later than 
accumulating 8,000 CSN if CSN is greater than 6,000 on the effective 
date of the AD. The FAA concurs and has changed this paragraph to 
require inspection within 2,000 CIS if a disk has over 6,000 CSN on the 
effective date of the AD.
    The same commenter suggests that at next engine shop visit would be 
sufficient as an interval for cooling hole and tie bolt hole 
inspections. The FAA does not concur. Since the timing of engine shop 
visits varies widely between operators, the use of shop visits to 
define inspection intervals in ADs does not provide adequate 
objectivity on which to assess the effectiveness of the required 
actions in addressing the unsafe condition. The FAA has determined that 
a maximum of 2,000 CIS interval is required.

[[Page 64516]]

    Subsequent to the publication of the proposed rule, two JT9D-7R4D/E 
operators indicated that the 6,000 CIS re-inspection interval for 
second stage turbine hub tie bolt hole mismachining would require them 
to remove engines prematurely due to their high cycle utilization rate. 
The FAA has determined through a review of risk analysis that the 
additional risk involved in extending the re-inspection interval from 
6,000 CIS to 8,000 CIS is sufficiently low and has changed the re-
inspection interval accordingly.
    In addition, the manufacturer has recommended that Special Process 
Operation Procedure (SPOP) 70 be used in lieu of SPOP 84 in order to 
permit the inspection of the second stage turbine hub tie bolt holes 
when the second stage turbine rotor is removed from the HPT module 
assembly without necessitating the removal of the second stage turbine 
blades. The FAA concurs and has changed the reference to the inspection 
procedure accordingly.
    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.
    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 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 removing amendment 39-6859 (56 FR 
5343, February 11, 1991) and by adding a new airworthiness directive, 
Amendment 39-10234, to read as follows:

97-25-10  Pratt & Whitney: Amendment 39-10234. Docket 97-ANE-04 
Supersedes airworthiness directive (AD) 91-04-10, Amendment 39-6859.

    Applicability: Pratt & Whitney (PW) JT9D-59A, -70A, -7Q, -7Q3, -
7R4D, -7R4D1, -7R4E, and -7R4E1 (AI-500) series turbofan engines, 
installed on but not limited to Airbus Industrie A300 and A310, 
Boeing 747 and 767, and McDonnell Douglas DC-10 series aircraft.

    Note 1: This 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 turbine disk failure due to cooling hole or tie bolt 
hole cracking, which could result in an uncontained engine failure 
and damage to the aircraft, accomplish the following:
    (a) For first stage high pressure turbine (HPT) disks, part 
numbers (P/Ns) 768001, 792701, 812901, 819801, 840501, 840401, 
840701, 840601, and 840301, installed in PW JT9D-59A, -70A, -7Q, and 
-7Q3 engines, accomplish the following:
    (1) Disks that have not been fluorescent penetrant inspected or 
eddy current inspected since introduction into service, perform an 
initial fluorescent penetrant inspection (FPI) for cracks in all 40 
cooling air holes in accordance with PW Turbojet Engine Standard 
Practices Manual, P/N 585005, Chapter/Section 70-33, Special Process 
Operation Procedure (SPOP) 84, as follows:
    (i) Disks with 3,500 cycles since new (CSN) or more on the 
effective date of this AD, inspect prior to accumulating 5,000 CSN, 
or within 1,500 cycles in service (CIS) after the effective date of 
this AD, whichever occurs later.
    (ii) Disks with less than 3,500 CSN on the effective date of 
this AD, inspect prior to accumulating 5,000 CSN.
    (2) Disks that have been reoperated in accordance with PW 
Service Bulletin (SB) No. 5815, Revision 2, dated July 31, 1992, or 
prior revisions, that have not been fluorescent penetrant inspected 
or eddy current inspected since reoperation, perform an initial FPI 
for cracks in all 40 cooling air holes in accordance with PW 
Turbojet Engine Standard Practices Manual, P/N 585005, Chapter/
Section 70-33, SPOP 84, as follows:
    (i) Disks with 3,500 CIS or more since reoperation on the 
effective date of this AD, inspect prior to accumulating 5,000 CIS 
since reoperation, or within 1,500 CIS after the effective date of 
this AD, whichever occurs later.
    (ii) Disks with less than 3,500 CIS since reoperation on the 
effective date of this AD, inspect prior to accumulating 5,000 CIS 
since reoperation.
    (3) Disks that have been fluorescent penetrant inspected, or 
eddy current inspected, since introduction into service or since 
reoperation, in accordance with PW SB No. 5744, Revision 3, dated 
March 31, 1993, or prior revisions, or PW JT9D-7Q, -7Q3 Engine 
Manual, P/N 777210, 72-51-00, Inspection -03, or PW JT9D-59A, -70A 
Engine Manual, P/N 754459, 72-51-00, Heavy Maintenance Check -03, 
perform an FPI for cracks in all 40 cooling air holes, prior to 
accumulating 3,500 CIS since last FPI or ECI, or within 250 CIS 
after the effective date of this AD, whichever occurs later, in 
accordance with PW Turbojet Engine Standard Practices Manual, P/N 
585005, Chapter/Section 70-33, SPOP 84.
    (4) Thereafter, perform FPI for cracks in all 40 cooling air 
holes at intervals not to exceed 3,500 CIS since last FPI, in 
accordance with PW Turbojet Engine Standard Practices Manual, P/N 
585005, Chapter/Section 70-33, SPOP 84.
    (5) Prior to further flight, remove from service cracked disks, 
and replace with serviceable parts.
    (b) For second stage HPT disks, P/N 5001802-01, installed in PW 
JT9D-7R4D, -7R4D1, -7R4E, and -7R4E1 (AI-500) engines, accomplish 
the following:
    (1) Disks that have not been fluorescent penetrant inspected 
since introduction into service, perform an initial FPI for cracks 
in all 30 tie bolt holes in accordance with PW Turbojet Engine 
Standard Practices Manual, P/N 585005, Chapter/Section 70-33, SPOP 
70, as follows:
    (i) Disks with 6,000 CSN or more on the effective date of this 
AD, inspect within 2,000 CIS after the effective date of this AD.

[[Page 64517]]

    (ii) Disks with less than 6,000 CSN on the effective date of 
this AD, inspect prior to accumulating 8,000 CSN.
    (2) Disks that have been fluorescent penetrant inspected since 
introduction into service, perform an FPI for cracks in all 30 tie 
bolt holes, prior to accumulating 8,000 CIS since last FPI, or 
within 250 CIS after the effective date of this AD, whichever occurs 
later, in accordance with PW Turbojet Engine Standard Practices 
Manual, P/N 585005, Chapter/Section 70-33, SPOP 70.
    (3) Thereafter, perform FPI for cracks in all 30 tie bolt holes 
at intervals not to exceed 8,000 CIS since last FPI, in accordance 
with PW Turbojet Engine Standard Practices Manual, P/N 585005, 
Chapter/Section 70-33, SPOP 70.
    (4) Prior to further flight, remove from service cracked disks, 
and replace with serviceable parts.
    (c) Report findings of cracked turbine disks within 48 hours 
after inspection to Tara Goodman, Aerospace Engineer, Engine 
Certification Office, FAA, Engine and Propeller Directorate, 12 New 
England Executive Park, Burlington, MA 01803-5299; telephone (781) 
238-7130, fax (781) 238-7199, Internet: 
``Tara.G[email protected]''. Reporting requirements have been 
approved by the Office of Management and Budget and assigned OMB 
control number 2120-0056.
    (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 method of compliance with this AD, if any, may be 
obtained from the Engine Certification Office.

    (e) 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.
    (f) This amendment becomes effective on January 12, 1998.

    Issued in Burlington, Massachusetts, on November 28, 1997.
Jay J. Pardee,
Manager, Engine and Propeller Directorate,
Aircraft Certification Service.
[FR Doc. 97-31965 Filed 12-5-97; 8:45 am]
BILLING CODE 4910-13-U