[Federal Register Volume 63, Number 219 (Friday, November 13, 1998)]
[Rules and Regulations]
[Pages 63393-63396]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-30332]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-ANE-21-AD; Amendment 39-10872; AD 98-23-07]
RIN 2120-AA64


Airworthiness Directives; Pratt & Whitney JT9D 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 certain Pratt & Whitney (PW) JT9D series turbofan 
engines, that requires a one-time acid etch inspection of the turbine 
exhaust case (TEC) wall between and on either side of the ``R'' and 
``S'' rails in the engine mount lug area (top quadrant of the case) for 
the presence of weld material, and if weld material is detected, 
removal from service and replacement with serviceable parts. This 
amendment is prompted by reports of weld rework performed in the outer 
case wall of the TEC, in the mount lug fillet area, during original 
production to address local under minimum wall thickness conditions 
which have left the TEC's structural capability compromised. The 
actions specified by this AD are intended to prevent TEC structural 
failure under abnormal operating conditions, which could result in 
reduced main mount load capability, engine separation from the wing and 
subsequent loss of control of the aircraft.

DATES: Effective January 12, 1999.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of January 12, 1999.

ADDRESSES: The service information referenced in this AD may be 
obtained from Pratt & Whitney, 400 Main St., East Hartford, CT 06108; 
telephone (860) 565-6600, 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: 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.


[[Page 63394]]


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 certain Pratt & Whitney (PW) 
Models JT9D-7, -7A, -7H, -7AH, -7F, -7J, -20, -20J, -7Q, -7Q3, -59A, -
70A, and -7R4D turbofan engines was published in the Federal Register 
on May 7, 1998 (63 FR 25179). That action proposed to require at the 
next removal of the TEC from the low pressure turbine case ``P'' flange 
for maintenance after the effective date of this AD, a one-time acid 
etch inspection of TEC wall between and on either side of the ``R'' and 
``S'' rails in the engine mount lug area (top quadrant of the case) for 
the presence of weld material, and if that material is detected, 
removal from service and replacement with serviceable parts.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Risk Assessment

    Several commenters question the risk assessment used to generate 
the proposed rule. The FAA will address each comment individually and 
provide responses.
    Two commenters state that a Continued Airworthiness Assessment 
Methodology (C.A.A.M.) analysis needs to be performed to validate the 
risk analysis submitted by the manufacturer for this rulemaking. The 
FAA does not concur. C.A.A.M. is a system of assessing and managing 
risk that includes the use of quantitative risk analysis models. The 
risk analysis submitted by the manufacturer to evaluate the subject 
unsafe condition followed the C.A.A.M. procedure.
    Two commenters indicate that utilizing data from one operator is 
insufficient to establish an appropriate risk factor. The FAA does not 
concur. The database of the one operator in question is extensive, 
since it represents a substantial portion of the engine fleet and 
includes detailed records of all inspections, and has been validated 
repeatedly against full-fleet experience.
    Two commenters object to the use of data from one operator based on 
that operator's hour-to-cycle mission profile. The FAA does not concur. 
Cracking in the mount lug area of the TEC is a function of high stress 
and temperature operation on a cyclic basis, and is independent of 
hours, time in service (TIS).
    One commenter takes issue with the assumption of constant fleet 
size and utilization. The FAA does not concur. The future rate of 
utilization is subject to a variety of factors, including resale and 
continued use of engines. The assumption of constant fleet size and 
utilization has been consistently used in previous risk analyses, 
therefore, this assumption allows comparison of this risk with other 
unsafe conditions.
    One commenter takes issue with the use of linear interpolation to 
predict failures instead of using Weibull analysis. The FAA does not 
concur. Weibull analysis was used to develop the failure distribution.
    One commenter notes it is not apparent that an assessment for 
incorrectly reading the acid etch is accounted for in the risk 
analysis. The FAA does not concur. The probability of correctly 
interpreting the macroetch results for the weld condition is high. This 
factor does not significantly affect the results of the risk analysis.
    One commenter postulates a lower risk of fan blade release coupled 
with a TEC with welds or cracks. The FAA does not concur. The FAA finds 
this calculation inaccurate because it: (1) includes only past 
occurrences for its estimate of the percent of the fleet with TEC 
cracks or welds and (2) it does not use the standard statistical 
practice for calculating mean time between failure.
    One commenter states that since there has never been a failure of 
the TEC from a full blade out or rotor seizure, the risk analysis is in 
question. The FAA does not concur. Corrective action does not need to 
occur as a result of a serious event. The FAA has determined that an 
unsafe condition exists and therefore this rulemaking is necessary as a 
proactive approach to continued airworthiness.
    Two commenters request the FAA direct PW to partner with the 
operators to develop a risk assessment, which takes into consideration 
specific data elements from the major affected operators to determine a 
logical and true safety risk and to postpone rulemaking until such time 
that this risk analysis can be reviewed. The FAA does not concur. The 
FAA has determined that the risk assessment evaluated for this 
rulemaking is appropriate. Since an unsafe condition has been 
determined to exist and is likely to develop on other products of the 
same type design, it is appropriate to issue this AD without further 
delay.

Other Comments

    Two commenters cite concerns about consistency for inspecting the 
primary mount locations on the TEC for the JT9D-7A/7F/7J models and the 
JT9D-20/20J models. The FAA concurs. Revision 1 of the SBs, referenced 
in this final rule, have corrected the inconsistency among engine 
models for the primary mount locations.
    Two commenters request that the economic impact of the proposal be 
revised to reflect case repairs and acquisition of new cases. The FAA 
concurs. There are 1,125 engines installed on aircraft of U.S. registry 
that would be affected by the inspection requirements of this AD. The 
average labor rate is $60 per work hour and it would take approximately 
1.4 work hours per engine to accomplish the acid etch inspection. For 
the inspection, then, the estimated impact is $94,500. The cost of 
replacement of a TEC found with welding in the primary mount lug area 
is approximately $495,000 per TEC. Since this AD addresses 23 TECs that 
are unaccounted for in the field, the estimated impact is $11,385,000. 
Therefore the total estimated cost impact of this AD is $11,479,000.
    One commenter notes that the proposed rule states the required 
actions must be taken at the next removal of the TEC from the low 
pressure turbine case ``P'' flange. If the phrase ``when the engine is 
in the shop,'' were added it would provide for exchanging a TEC in the 
hangar during an aircraft service. Normally when a TEC is replaced in 
the hangar, an overhauled case is obtained from a vendor. However, on 
occasion, a TEC is obtained from another engine and a small airline 
needs this flexibility. The FAA concurs. The FAA has revised the shop 
visit definition in the compliance section of this final rule to 
induction of the engine into the shop for scheduled maintenance.
    One commenter states that they are currently inspecting the TECs to 
the original SB and the Internal Engineering Notice (IEN) noted in PW 
All Operators Wire (AOW). The commenter requests the AD indicate the 
original of SB 6322, A72-546 and IEN 97ECO56C as compliance with the 
AD. The FAA concurs. In the interest of time to alert operators of the 
need to conduct the inspection, PW issued an AOW citing the IEN number 
97ECO56C which is used within PW to issue the original SB. The IEN for 
Revision 1 to SB 6322 and A72-546 were issued before the NPRM was 
released and provided better etching agents the operator can use for 
the inspection and referenced acid etch inspection for only the primary 
mount lug locations. Since complying with the original SBs is more 
restrictive than Revision 1, this final rule has been revised to 
reference the original issue of the affected SBs.
    One commenter concurs with the rule as proposed.

[[Page 63395]]

Additional Technical Concerns

    The following technical concerns were raised in comments to the 
proposed rule, but do not request any specific changes to the rule as 
proposed, however the FAA will answer these technical concerns.
    One commenter asks if the full fan blade out test data was not 
required for SB 4853 why is a full fan blade out test required to 
evaluate welds in mount areas? The commenter also asks why is the 
static deflection load test data presented to the FAA for welds in the 
mount areas not admissible as substantiation, when PW considered static 
load test data admissible for mount lug area modifications? The FAA 
does not concur. The objective of SB 4853 is to address cracking in the 
TEC struts and rails and does not address the case wall. Also, PW did 
not submit data to substantiate weld repairs in the primary mount lug 
areas, and no other design approvals allowing for weld repairs in the 
primary mount lug areas have been issued by the FAA.
    One commenter refers to AD 96-25-10 (Docket 95-ANE-57) that 
requires JT9D TEC modification to increase the containment capability 
and includes the option of welding doublers on the inside surface of 
the TEC or welding a thicker replacement flange onto the case, and then 
asks why is the FAA unconcerned about the TEC's ability to withstand a 
full fan blade out or rotor seizure for a case that has a 360 degree 
weld approximately 1.2'' away from the mount bosses? The FAA does not 
concur. Welds associated with the P flange replacement and containment 
shields are outside the high stress zone of the primary mount lug 
locations.
    Two commenters request that the Chromalloy ``strongback'' repair be 
listed as a means for compliance with the AD. The FAA does not concur. 
The repair has not been approved by the FAA nor does it provide an 
alternate method of compliance to the AD as proposed. The AD method of 
compliance is to perform an acid etch and conduct an inspection, 
therefore the Chromalloy repair is considered outside the scope of this 
AD.
    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 adding the following new 
airworthiness directive:

98-23-07 Pratt & Whitney: Amendment 39-10872. Docket 98-ANE-21-AD.
    Applicability: Pratt & Whitney (PW) Models JT9D-7, -7A, -7H, -
7AH, -7F, -7J, -20, -20J, -7Q, -7Q3, -59A, -70A, and -7R4D turbofan 
engines. These engines are installed on but not limited to Boeing 
747 and 767 series, McDonnell Douglas DC-10 series, and Airbus A300 
and A310 series aircraft.

    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 (c) 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 exhaust case (TEC) structural failure under 
abnormal operating conditions, which could result in reduced main 
mount load capability, engine separation from the wing and 
subsequent loss of aircraft control, accomplish the following:
    (a) At the next shop visit after the effective date of this AD, 
accomplish the following in accordance with PW Alert Service 
Bulletin (ASB) No. JT9D-A6322, Revision 1, dated August 13, 1998, or 
Original, dated March 19, 1998, or ASB No. JT9D-7R4-A72-546, 
Revision 1, dated August 13, 1998, or Original, dated March 19, 
1998, as applicable:
    (1) Perform a one-time acid etch inspection of TEC wall between 
and on either side of the ``R'' and ``S'' rails in the engine mount 
lug area (top quadrant of the case) for the presence of weld 
material.
    (2) If weld material is found, remove from service the TEC and 
replace with a serviceable part.
    (b) For the purpose of this AD, a shop visit is defined as the 
induction of an engine into a shop for the purpose of maintenance.
    (c) 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 request 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.

    (d) 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.
    (e) The actions required by this AD shall be done in accordance 
with the following PW ASBs:

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           Document No.                      Pages                   Revision                     Date
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JT9D-7R4-A72-546.................  1-4.....................  1.......................  August 13, 1998.

[[Page 63396]]

                                   5.......................  Original................  March 19, 1998.
                                   6-9.....................  1.......................  August 13, 1998.
                                   10, 11..................  Original................  March 19, 1998.
                                   12-19...................  1.......................  August 13, 1998.
    Total Pages: 19
JT9D-7R4-A72-546.................  1-16....................  Original................  March 19, 1998.
    Total Pages: 16.
A6322............................  1-4.....................  1.......................  August 13, 1998.
                                   5-22....................  Original................  March 19, 1998.
                                   23-29...................  1.......................  August 13, 1998.
                                   30, 31..................  Original................  March 19, 1998.
                                   32-45...................  1.......................  August 13, 1998.
    Total Pages: 45.
A6322............................  1-41....................  Original................  March 19, 1998.
    Total Pages: 41.
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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 St., 
East Hartford, CT 06108; telephone (860) 565-6600, 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.
    (f) This amendment becomes effective on January 12, 1999.

    Issued in Burlington, Massachusetts, on November 5, 1998.
David A. Downey,
Assistant Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 98-30332 Filed 11-12-98; 8:45 am]
BILLING CODE 4910-13-P