[Federal Register Volume 61, Number 225 (Wednesday, November 20, 1996)]
[Rules and Regulations]
[Pages 58975-58978]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-28988]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-ANE-45; Amendment 39-9815; AD 96-23-10]
RIN 2120-AA64


Airworthiness Directives; Pratt & Whitney JT3D 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 Pratt & Whitney (PW) JT3D series turbofan engines, that 
requires inspection of steel high pressure compressor (HPC) disks for 
corrosion, recoating or replating those disks, or replacing those disks 
as necessary. This amendment is prompted by reports of a failure of a 
PW JT8D steel HPC disk, which is similar in design to the PW JT3D steel 
HPC disks. The actions specified by this AD are intended to prevent 
steel HPC disk failure due to corrosion, which could result in an 
uncontained engine failure and damage to the aircraft.

DATES: Effective January 21, 1997.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of January 21, 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

[[Page 58976]]

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: Barbara Caufield, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone (617) 
238-7146, 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) JT3D series 
turbofan engines was published in the Federal Register on October 31, 
1995 (60 FR 53337). That action proposed to require inspection of steel 
high pressure compressor (HPC) disks, stages 10-15, for corrosion, 
recoating or replating those disks, or replacing those disks as 
necessary in accordance with PW Alert Service Bulletin (ASB) No. A6208, 
Revision 2, dated July 7, 1995.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    Twelve commenters state that the compliance time to accomplish the 
AD should be extended. The commenters state that due to the complex 
workscope, aircraft down time, high cost, severe economic and 
operational burden, significant impact on parts procurement, and shop 
availability, the compliance times need to be extended. Times suggested 
range from four to seven years, or next shop visit, or at exposure. 
Pratt & Whitney has updated their risk analysis based on new data 
provided by operators and a study concerning disk fractures resulting 
in uncontained events. Based on this update they have revised Alert 
Service Bulletin (ASB) No. A6208, extending the threshold and drawdown 
intervals. The FAA concurs in part. The FAA has reviewed and approved 
the technical contents of PW ASB No. A6208, Revision 3, dated January 
11, 1996, and therefore the compliance time will be extended to that 
included in the ASB based on PW's risk analysis. Other intervals 
proposed are not technically justified.
    Nineteen commenters state that the cost estimate in the NPRM is too 
low since that estimate does not include the cost of additional 
maintenance required under Part 121 (additional parts that must be 
replaced that are unrelated to the AD requirements); engine testing, 
fuel, oil, transportation/shipping, aircraft downtime, etc. The FAA 
does not concur. The FAA's cost estimate is based on information from 
the engine manufacturer to remove and replace the engine, teardown and 
replacement of a percentage of HPC disks, and engine buildup. It does 
not include costs not directly associated with the AD, because those 
costs result from other maintenance requirements. The compliance 
schedule of this AD allows for operators to schedule the required 
actions with other, normally scheduled maintenance, thereby minimizing 
the direct costs of the AD.
    Six commenters state that part availability and shop capacity are 
not adequate for the fleet to perform the AD. There is only one source 
for new parts, and the supplier will not be able to keep up with the 
demand for new disks and other parts. Some operators will not be able 
to obtain parts to meet AD requirements. Operators will be competing 
for shop space at the limited number of repair shops during a 
restricted period of time. The FAA does not concur. The manufacturer 
has advised the FAA that parts will be available to meet demand. In 
addition, the FAA has determined, based on repair station input, that 
shop capacity over the extended compliance time of this AD will be 
satisfactory.
    Eleven commenters state that there have been no PW JT3D disk 
failures due to corrosion, and therefore no flight safety problem 
exists, and that the AD should be withdrawn. The FAA does not concur. 
Although there have been no known PW JT3D series disk failures to date 
attributable to corrosion, the risk analysis by PW shows that if 
corrosion inspection is not accomplished in accordance with the 
applicable Service Bulletins' schedules the probability of a disk 
fracture is unacceptably high.
    Eight commenters question using JT8D experience as the basis for 
this AD, as no consideration was given to differences in engine 
application: i.e., four-engine versus twin-engine; that the PW JT3D 
disk is heavier, and therefore has adequate safety margin; and that the 
PW JT3D disk operates at slower speeds, different temperatures and 
pressures. The FAA concurs in part. The commenters are correct in that 
AD action was initiated because of similarity between the engines; 
however, the analysis to generate inspection intervals and drawdown 
times used data specific to the PW JT3D series.
    Four commenters suggest that PW test a JT3D disk to failure to 
evaluate the need for an AD and to verify the failure mode. The FAA 
does not concur. The FAA determined that an unsafe condition exists 
based on an actual failure of a similarly designed disk and a risk 
analysis using JT3D data. No further testing is necessary, and the FAA 
has concluded that the actions required by this AD are necessary to 
address that unsafe condition.
    Two commenters request a meeting between FAA, PW, and industry. The 
FAA does not concur. A meeting was held with PW and a group of 
operators in August 1995 prior to the publication of the NPRM; PW 
requested operator input data for risk analysis at that time.
    Three commenters state that only limited numbers of JT3D disks were 
analyzed by PW in their risk analysis. The FAA does not concur. Since 
publication of the NPRM, PW updated their risk analysis based on 
additional data supplied by JT3D operators and the new data confirms 
the earlier findings.
    Three commenters state that the FAA underestimated the number of 
affected engines in the economic analysis, and that 6,000 engines 
worldwide are affected, including military and foreign. The FAA does 
not concur. The FAA does not include military engines in its economic 
analyses; these only refer to the civilian fleet.
    Two commenters state that the AD should take operators' maintenance 
programs into consideration and give flexible compliance schedules 
based on maintenance programs. Operators' current disk inspection and 
maintenance practices call for inspection of HPC disks for corrosion, 
recoating, replating, or replacement. The FAA does not concur. The 
criticality of this inspection warrants that it be separate and 
distinct from routine maintenance tasks.
    One commenter states that the FAA should consider using half-life 
inspection on life-limited parts in conjunction with studies conducted 
on HPC disks (based on the NPRM's statement ``corrosion is more apt to 
occur if the steel HPC disk is not recoated/replated during its life 
span and retains original production protective coating/plating.'') The 
FAA does not concur. The referenced statement from the NPRM is for 
informational purposes only, and the compliance time is based on PW's 
risk analysis, which takes into account many factors, including disk 
geometry, stress distribution, critical corrosion pit depth, crack 
propagation rates, and engine utilization rates.
    One commenter states that the FAA should allow metallurgists 
appointed by operators to explore available data from

[[Page 58977]]

PW and examine how the correlation between PW JT8D and JT3D disks were 
achieved, as the commenter does not accept the manufacturer's 
conclusions. The FAA does not concur. Operators were given the 
opportunity to present differing findings during the meeting that was 
held with PW and a group of operators in August 1995.
    One commenter states that there is no need for the AD as industry 
is currently complying with the ASB. The FAA does not concur. 
Airworthiness directive action is necessary to ensure compliance.
    One commenter states that they were not consulted by the FAA prior 
to the issuance of the NPRM, that their operational service experience 
with HPC disks was not taken into account, and, accordingly, the AD 
should not issue. The FAA does not concur. The FAA, as a rule, does not 
usually consult with individual operators to gather facts for the 
development of an airworthiness directive. The FAA does, however, 
consult with the manufacturer of the product and industry groups and 
associations. For this AD, the FAA did solicit input from Pratt & 
Whitney, who, in turn, solicited input from operators for inclusion in 
the risk analysis.
    Two commenters agree with the rule as proposed.
    Since publication of the NPRM, the FAA has received additional 
economic data from the manufacturer and has recalculated the economic 
analysis to reflect this new information.
    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 2,000 engines of the affected design in the 
worldwide fleet. The FAA estimates that 1,000 engines installed on 
aircraft of U.S. registry will be affected by this AD. Based on 
domestic fleet-wide data, the FAA estimates that approximately 40%, or 
400 engines, will be required to be removed at times other than 
regularly scheduled maintenance to accomplish the AD's actions. 
Approximately 16 work hours are necessary to remove and replace the 
engine, and the average labor rate is $60 per work hour. Approximately 
100 work hours are required to teardown and rebuild the engine. The FAA 
estimates that approximately 15% of disks removed from engines will 
need to be scrapped at a cost of $9,000 per engine. Based on these 
figures, the total cost impact of the AD on U.S. operators is estimated 
to be $33,384,000 over a 15-year period.
    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:

96-23-10--Pratt & Whitney: Amendment 39-9815. Docket 95- ANE-45.

    Applicability: Pratt & Whitney (PW) Models JT3D-1, -1A, -3, -3B, 
-3C, -1-MC6, -1A-MC6, -1-MC7, -1A-MC7, -7, -7A turbofan engines, 
installed on but not limited to Boeing 707 and 720 series aircraft 
and McDonnell Douglas DC-8 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 steel high pressure compressor (HPC) disk failure due 
to corrosion, which could result in an uncontained engine failure 
and damage to the aircraft, accomplish the following:
    (a) Inspect steel HPC disks, stages 10-15, for corrosion, recoat 
or replate, or replace as necessary, in accordance with PW Alert 
Service Bulletin (ASB) No. A6208, Revision 3, dated January 11, 
1996, and the following schedule:
    (1) For disks coated with PWA 110-2/-3 Aluminide (non top coat 
system) and for disks with unknown coating or plating, as follows:
    (i) Initially inspect, recoat or replate, or replace as 
necessary, within 14 years since new or since last recoat or 
replate, or within 36 months after the effective date of this AD, 
whichever occurs later.
    (ii) Thereafter, inspect, recoat or replate, or replace as 
necessary, at intervals not to exceed 14 years since new or last 
coating, if PWA 110-2/-3 Aluminide (non top coat system) is applied, 
or not to exceed 15 years since new or last plating, if PWA 110-21/-
31 Aluminide (top coat system) or Nickel Cadmium (NI-CAD) plating is 
applied.
    (2) For disks coated with PWA 110-21/-31 Aluminide (top coat 
system) or plated with NI-CAD, as follows:
    (i) Initially inspect, recoat or replate, or replace as 
necessary, within 15 years since new or since last replate, or 
within 36 months after the effective date of this AD, whichever 
occurs later.
    (ii) Thereafter, inspect, recoat or replate, or replace as 
necessary, at intervals not to exceed 14 years since new or last 
coating, if PWA 110-2/-3 Aluminide (non top coat system) is applied, 
or not to exceed 15 years since new or last plating, if PWA 110-21/-
31 Aluminide (top coat system) or Nickel Cadmium (NI-CAD) plating is 
applied.
    (3) For disks with unknown coating or plating, and unknown time 
since last coating or plating; or for disks with known coating or 
plating and unknown time since last coating or plating, as follows:
    (i) Initially inspect, recoat or replate, or replace as 
necessary, within 36 months after the effective date of this AD.
    (ii) Thereafter, inspect, recoat or replate, or replace as 
necessary, at intervals not to exceed 14 years since new or last 
coating, if PWA 110-2/-3 Aluminide (non top coat system) is applied, 
or not to exceed 15 years since new or last plating, if PWA 110-21/-
31 Aluminide (top coat system) or Nickel Cadmium (NI-CAD) plating is 
applied.
    (b) An alternative method of compliance or adjustment of the 
compliance time that

[[Page 58978]]

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 ASB:

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                  Document No.                     Pages    Revision                     Date                   
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A6208..........................................     1              3  Jan. 11, 1996.                            
                                                    2              1  May 8, 1995.                              
                                                    3              3  Jan. 11, 1996.                            
                                                    4              1  May 8, 1995.                              
                                                    5-9            3  Jan. 11, 1996                             
                                                    10-18          1  May 8, 1995.                              
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Total Pages: 18.                                                                                                

    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 January 21, 1997.

    Issued in Burlington, Massachusetts, on November 1, 1996.
James C. Jones,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 96-28988 Filed 11-19-96; 8:45 am]
BILLING CODE 4910-13-U