[Federal Register Volume 61, Number 245 (Thursday, December 19, 1996)]
[Rules and Regulations]
[Pages 66892-66896]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-31947]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-ANE-57; Amendment 39-9853; AD 96-25-10]
RIN 2120-AA64


Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan 
Engines

AGENCY: Federal Aviation Administration, DOT.


[[Page 66893]]


ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to Pratt & Whitney JT9D series turbofan engines, that 
requires installing an improved design turbine exhaust case (TEC) with 
a thicker containment wall, modifying the existing TEC to incorporate a 
containment shield, or modifying the existing TEC to replace the ``P'' 
flange and case wall. This amendment is prompted by reports of 64 
uncontained engine failures since 1972. The actions specified by this 
AD are intended to prevent release of uncontained debris from the TEC 
following an internal engine failure, which can result in damage to the 
aircraft.

DATES: Effective February 18, 1997.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of February 18, 1997.

ADDRESSES: The service information referenced in this AD may be 
obtained from Pratt & Whitney, Publications Department, Supervisor 
Technical Publications Distribution, M/S 132-30, 400 Main St., East 
Hartford, CT 06108; telephone (860) 565-7700, fax (860) 565-4503. 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; 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: 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 Pratt & Whitney (PW) JT9D series 
turbofan engines was published in the Federal Register on June 5, 1996 
(61 FR 28520). That action proposed to require installing an improved 
design turbine exhaust case (TEC) with a thicker containment wall, 
modifying the existing TEC to incorporate a containment shield, or 
modifying the existing TEC to replace the ``P'' flange and case wall.
    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 the proposed modification of the TEC as a 
solution to preventing uncontained engine failure is unnecessary since 
there are modifications and inspection programs available that 
specifically address the root causes for those events that led to 
uncontained engine failures. The commenter points out that of the 64 
incidents of TEC penetration, all but one event are addressed by other 
mandated actions. The FAA does not concur. Since January 1993, when the 
FAA first considered issuance of an AD for TEC containment, three 
additional conditions have occurred that the FAA considers warranting 
AD action at this time. First, there have been new root cause problems 
resulting in TEC penetrations; second the rate of uncontained engine 
failures has increased; and third, more substantial damage to the 
engine and aircraft has occurred. The discovery of new root causes of 
failures demonstrates that failures and subsequent uncontainments 
result from a wider variety of reasons than previously believed. The 
causal factors for these uncontainments include maintenance, design 
deficiencies, manufacturing defects, corrosion, foreign object damage, 
etc. The FAA has determined that even with the best available 
strategies for addressing the root cause of engine failures, the FAA 
expects that new failure modes and failure sequences could exist. As a 
result, the FAA anticipates further challenges to the TEC containment 
structure, and has determined that the necessary containment 
modifications must be implemented through an AD as proposed.
    In response to the comment that the root cause of all but one of 
the 64 referenced uncontained events are addressed by current mandatory 
action, the FAA does not concur. Additional review of the TEC 
penetration history reveals multiple incidents in which the root cause 
was undetermined, or in which no mandatory action by AD is required, or 
in which operators inadvertently did not comply with AD action, or in 
which improper repair or inspection was performed on certain engine 
components.
    One commenter states that a probabilistic risk assessment 
accomplished by PW in October 1995 concludes that there is insufficient 
risk to mandate TEC modification. The FAA does not concur. The risk 
assessment performed by PW is a structured approach that enables the 
FAA to better assess and target critical areas and prioritize 
resources. It is also necessary to emphasize that risk assessment is 
not the only means of determining the need for mandatory corrective 
action, and that other parameters such as incidence rate, failure 
modes, restoration of certification basis, and basic engineering 
judgment are also utilized. The FAA has determined that for the TEC 
penetration issue all these other factors result in the need to issue 
an AD.
    One commenter states that the FAA cost assessment of approximately 
$2,500 per engine to accomplish the proposed actions is based on the 
accomplishment of the option to weld shields to provide increased wall 
thickness. For some operators this is not a preferred option. The FAA 
concurs in part. The FAA has provided industry three options for 
compliance with the proposed AD. These options, in terms of decreasing 
cost, are as follows: a new thick wall TEC, a modified TEC with a new, 
thicker ``P'' flange, and finally welding on containment shields. 
Several operators have expressed concern with the durability of the 
welded containment shields option and take exception to the fact that 
the FAA utilized this option for the AD cost assessment. This operator 
plans to utilize one of the more costly methods for compliance with the 
AD. The FAA has reviewed all three options for enhanced containment and 
concludes that all three satisfy Part 33 of the Federal Aviation 
Regulations (FAR) (14 CFR part 33) requirements. The FAA performed the 
cost assessment utilizing the containment shield option since it has 
the least economic impact, and the FAA has reason to believe that the 
majority of operators will utilize this option, which has sound design 
and durability in accordance with FAR Part 33. The FAA understands that 
a new case would have greater longevity, and that the new ``P'' flange 
may be necessary when the existing ``P'' flange is no longer 
serviceable. In conclusion, this AD leaves it to the discretion of the 
operator the choice of option and provides all three options as 
approved type designs.
    One commenter states that the containment shields are not an 
acceptable option, due to the fact that the shields could lead to 
corrosion of the TEC inner wall, which could compromise the structural 
integrity of the TEC. The FAA does not concur. The FAA has performed a 
thorough technical review of the proposed containment shields. As part 
of this review, multiple TECs were returned from service and have had 
their shields removed with subsequent sectioning of the case wall and 
shields for evaluation of corrosion extent. In this review no case 
walls were found with corrosion

[[Page 66894]]

that compromised case wall thickness. In addition, no residual material 
was found that would suggest entrapment of foreign substances. The 
shields themselves also exhibited no corrosion that compromises type 
design wall thickness. This commenter states that the current cleaning 
and inspection procedures may have the potential for entrapment of 
cleaning and inspection solutions between the case wall and containment 
shields. The FAA has studied this concern and does not believe this is 
a problem. The FAA has determined that the containment shields are 
attached with a stitch weld, which will allow for sufficient purging of 
potentially corrosive solutions. When the TECs were sectioned in the 
evaluation, no residual deposits of cleaning or inspection solutions 
were found. However, to assure that corrosion due to potential 
entrapment of cleaning or inspection fluids is mitigated, the 
manufacturer is developing enhanced inspection and cleaning procedures 
in the engine overhaul manual.
    One commenter states that they hold two Supplemental Type 
Certificates (STCs) that provide for modification of the TEC by the 
installation of a thicker containment wall, and requests inclusion of 
these STCs as a means of compliance to the AD. The FAA concurs and has 
revised this final rule accordingly.
    One commenter states that the inclusion of an STC in the AD as an 
alternative method of compliance gives the STC holder an unfair 
marketing advantage. The commenter requests that their company approved 
repair be listed in the text of the AD with the STC. The FAA does not 
concur. The AD identifies all known type designs and, as such, the STC 
is an FAA-approved type design. The commenter does not hold a design 
approval and therefore cannot be listed as a method of compliance to 
this AD. The commenter is listed in the PW SB as a source acceptable to 
PW for performing the approved repair. Therefore, the FAA would 
consider them an acceptable source for repair.
    One commenter states that due to variations in incidence rate for 
uncontained TEC penetrations by engine model, i.e., JT9D-7, JT9D-7Q, 
and JT9D-7R4, that the FAA should adjust the proposed AD to be engine 
model specific. The FAA does not concur. The FAA finds that any 
variation in incident rate is not a significant enough factor to 
warrant providing a model-specific inspection interval.
    Since issuance of the NPRM, the FAA has received a report that 
certain PW JT9D-7R4 TECs were modified improperly. These TECs have a 
soft material condition, which renders them incapable of properly 
containing debris, as required by this AD. These TECs were modified to 
incorporate a replacement ``P'' flange and case wall in accordance with 
PW SB No. JT9D-7R4-72-513, Revision 3, November 13, 1996, or prior 
revisions. This final rule AD adds a paragraph to the compliance 
section requiring heat treatment of all TECs modified in accordance 
with PW SB No. JT9D-7R4-72-513, Revision 3, November 13, 1996, or prior 
revisions, in accordance with PW SB No. JT9D-7R4-72-534, dated October 
18, 1996.
    In addition, PW has issued SB No. 6157, Revision 1, dated July 17, 
1996, which only differs from the original by adding additional repair 
stations. This final rule AD references Revision 1 of this SB.
    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.
    There are approximately 2,748 engines of the affected design in the 
worldwide fleet. The FAA estimates that 740 engines installed on 
aircraft of U.S. registry will be affected by this AD, that it will 
take approximately 14 work hours per engine to accomplish the required 
actions, and that the average labor rate is $60 per work hour. Required 
parts will cost approximately $1,404 per engine. Based on these 
figures, the total cost impact of the AD on U.S. operators is estimated 
to be $1,660,560.
    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 USC 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

96-25-10  Pratt & Whitney: Amendment 39-9853. Docket 95-ANE-57.

    Applicability: Pratt & Whitney (PW) JT9D-3, -7, -20, -59A, -70A, 
-7Q, and -7R4 series turbofan engines, installed on but not limited 
to Airbus A300 and A310 series; Boeing 747 and 767 series; and 
McDonnell Douglas DC-10 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 (b) 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 release of uncontained debris from the turbine 
exhaust case (TEC) following an internal engine failure, which can 
result in damage to the aircraft, accomplish the following:
    (a) At the next removal of the TEC from the low pressure turbine 
case ``P'' flange for overhaul, where the No. 4 bearing, carbon 
seals, lubrication pressurization lines, or scavenge lines are 
removed for maintenance after the effective date of this AD, but not 
later than 48 months after the effective date of this AD, accomplish 
the following:

[[Page 66895]]

    (1) For PW JT9D-3A, -7, -7A, -7AH, -7H, -7F, -7J, -20, and -20J 
series turbofan engines, accomplish any one of the following 
actions:
    (i) Install a thicker-walled TEC, with Part Numbers (P/N's) 
listed in PW SB No. 6113, dated April 13, 1993, as applicable; or
    (ii) Install a modified TEC that incorporates a containment 
shield, with P/N's listed in PW SB No. 5907, dated March 27, 1990, 
as applicable; or
    (iii) Install a modified TEC that incorporates a replacement 
``P'' flange and case wall, with P/N's listed in PW SB No. 6118, 
Revision 3, dated January 10, 1996, or
    (iv) Install a modified TEC that incorporates a replacement 
``P'' flange and case wall, with Chromalloy Supplemental Type 
Certificate (STC) SE00047AT-D, dated October 15, 1996.
    (2) For PW JT9D-7Q and -7Q3 series turbofan engines, accomplish 
any one of the following actions:
    (i) Install a thicker-walled TEC, with P/N's listed in PW SB No. 
5977, dated December 14, 1990; or
    (ii) Install a modified TEC that incorporates a containment 
shield, with P/N's listed in PW SB No. 5907, dated March 27, 1990, 
as applicable; or
    (iii) Install a modified TEC that incorporates a replacement 
``P'' flange and case wall, with P/N's listed in PW SB No. 6157, 
Revision 1, dated July 17, 1996; or
    (iv) Install a modified TEC that incorporates a replacement 
``P'' flange and case wall, with Chromalloy STC SE00047AT-D, dated 
October 15, 1996.
    (3) For PW JT9D-59A and -70A series turbofan engines, accomplish 
one of the following actions:
    (i) Install a thicker-walled TEC, with P/N's listed in PW SB No. 
6243, dated February 1, 1996; or
    (ii) Install a modified TEC that incorporates a containment 
shield, with P/N's listed in PW SB No. 5907, dated March 27, 1990, 
as applicable;
    (iii) Install a modified TEC that incorporates a replacement 
``P'' flange and case wall, with P/N's listed in PW SB No. 6157, 
Revision 1, dated July 17, 1996; or
    (iv) Install a modified TEC that incorporates a replacement 
``P'' flange and case wall, with Chromalloy STC SE00047AT-D, dated 
October 15, 1996.
    (4) For PW JT9D-7R4D (BG-700 series) turbofan engines, 
accomplish one of the following actions:
    (i) Install a thicker-walled TEC, with P/N's listed in PW SB No. 
JT9D-7R4-72-479, Revision 1, dated November 12, 1993; or
    (ii) Install a modified TEC that incorporates a containment 
shield, with P/N's listed in PW SB No. JT9D-7R4-72-407, Revision 1, 
dated August 16, 1990, as applicable; or
    (iii) Install a modified TEC that incorporates a replacement 
``P'' flange and case wall, with Chromalloy STC SE00047AT-D, dated 
October 15, 1996.
    (5) For PW JT9D-7R4D (BG-800 series), -7R4D (BG-900 series), -
7R4D1 (AI-500 series), -7R4E (BG-800 series), -7R4E (BG-900 series), 
-7R4E1 (AI-500 series), -7R4E1 (AI-600 series), -7R4E4 (BG-900 
series), -7R4G2 (BG-300 series), and -7R4H1 (AI-600 series) turbofan 
engines, accomplish any one of the following actions:
    (i) Install a thicker-walled TEC, with P/N's listed in PW SB No. 
JT9D-7R4-72-534, dated October 18, 1996; or
    (ii) Install a modified TEC that incorporates a containment 
shield, with P/N's listed in PW SB No. JT9D-7R4-72-466, Revision 2, 
dated May 10, 1996; or
    (iii) Install a modified TEC that incorporates a replacement 
``P'' flange and case wall, with P/N's listed in PW SB No. JT9D-7R4-
72-534, dated October 18, 1996; or
    (iv) Install a modified TEC that incorporates a replacement 
``P'' flange and case wall, with Chromalloy STC SE00054AT-D, dated 
October 19, 1994.
    (6) For PW JT9D-7R4D (BG-800 series), -7R4D (BG-900 series), -
7R4D1 (AI-500 series), -7R4E (BG-800 series), -7R4E (BG-900 series), 
-7R4E1 (AI-500 series), -7R4E1 (AI-600 series), -7R4E4 (BG-900 
series), -7R4G2 (BG-300 series), and -7R4H1 (AI-600 series) turbofan 
engines, with TECs that have been modified to incorporate a 
replacement flange and case wall, in accordance with PW SB No. JT9D-
7R4-72-513, Revision 3, dated November 13, 1996, or previous 
revisions, perform heat treatment of the TECs in accordance with the 
Accomplishment Instructions of PW SB No. JT9D-7R4-72-534, dated 
October 18, 1996.
    (b) 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 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.

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

----------------------------------------------------------------------------------------------------------------
           Document No.              Pages            Revision                            Date                  
----------------------------------------------------------------------------------------------------------------
SB No. 6113......................       1-38  Original................  April 13, 1993.                         
    Total pages: 38.                                                                                            
SB No. 5977......................        1-6  Original................  December 14, 1990.                      
    Total pages: 6.                                                                                             
SB No. JT9D-7R4-72-479...........          1  1.......................  November 12, 1993.                      
                                        2, 3  Original................  February 25, 1993.                      
                                         4-6  1.......................  November 12, 1993.                      
    Total pages: 6.                                                                                             
SB No. 6243......................        1-6  Original................  February 1, 1996.                       
    Total pages: 6.                                                                                             
SB No. JT9D-7R4-72-513...........       1-19  3.......................  November 13, 1996.                      
    Total pages: 19.                                                                                            
SB No. JT9D-7R4-72-534...........     1-26 5  Original................  October 18, 1996.                       
    Total pages: 26.                                                                                            
SB No. 5907......................       1-32  Original................  March 27, 1990.                         
    Total pages: 32.                                                                                            
SB No. JT9D-7R4-72-407...........          1  1.......................  August, 16, 1990.                       
                                         2-5  Original................  March 30, 1990.                         
                                           6  1.......................  August 16, 1990.                        
                                        7-22  Original................  March 30, 1990.                         
    Total pages: 22.                                                                                            
SB No. JT9D-7R4-72-466...........       1, 2  2.......................  May 10, 1996.                           
                                         3-8  Original................  January 15, 1993.                       
                                        9-11  1.......................  March 4, 1994.                          
                                      12, 13  Original................  January 15, 1993.                       
                                       14-16  1.......................  March 4, 1994.                          
                                      17, 18  Original................  January 15, 1993.                       

[[Page 66896]]

                                                                                                                
    Total pages: 18.                                                                                            
SB No. 6118......................          1  3.......................  January 10, 1996.                       
                                         2-5  2.......................  April 18, 1995.                         
                                        6-32  Original................  April 15, 1993.                         
                                          33  2.......................  April 18, 1995.                         
                                       34-38  Original................  April 15, 1993.                         
                                          39  1.......................  May 20, 1993.                           
                                          40  Original................  April 15, 1993.                         
                                       41-44  1.......................  May 20, 1993.                           
                                          45  3.......................  January 10, 1996.                       
    Total pages: 45.                                                                                            
SB No. 6157......................          1  1.......................  July 17, 1996.                          
                                        2-15  Original................  February 9, 1994.                       
                                          16  1.......................  July 17, 1996.                          
    Total pages: 16.                                                                                            
----------------------------------------------------------------------------------------------------------------

    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, Publications 
Department, Supervisor Technical Publications Distribution, M/S 132-
30, 400 Main St., East Hartford, CT 06108; telephone (860) 565-7700, 
fax (860) 565-4503. 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.
    (e) This amendment becomes effective on February 18, 1997.

    Issued in Burlington, Massachusetts, on December 4, 1996.
James C. Jones,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 96-31947 Filed 12-18-96; 8:45 am]
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