[Federal Register Volume 59, Number 186 (Tuesday, September 27, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-23326]


[[Page Unknown]]

[Federal Register: September 27, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 92-ANE-44; Amendment 39-9029; AD 94-20-01]

 

Airworthiness Directives; Pratt & Whitney JT8D 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) JT8D series turbofan engines, that 
requires a determination of the utilization rate and coating type of 
the 7th, 8th, 9th, 10th, 11th, and 12th high pressure compressor (HPC) 
disks, and removal, inspection for corrosion, and recoating of those 
HPC disks based on utilization rate. This amendment is prompted by an 
investigation into an uncontained PW JT8D engine failure caused by 
severe corrosion on the 9th stage HPC disk. The actions specified by 
this AD are intended to prevent fracture of the HPC disks, which can 
result in uncontained release of engine fragments, inflight engine 
shutdown, and airframe damage.

DATES: Effective November 28, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of November 28, 1994.

ADDRESSES: The service information referenced in this AD may be 
obtained from Pratt & Whitney, Publications Department, 400 Main 
Street, East Hartford, CT 06108. 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: Mark A. Rumizen, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone no. 
(617) 238-7137, 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) JT8D series 
turbofan engines was published in the Federal Register on July 27, 1993 
(58 FR 40079). That action proposed to require a record search, initial 
and repetitive on-wing and shop inspections to detect corrosion on high 
pressure compressor (HPC) disks, and removal from service of engines 
with HPC disks corroded beyond serviceable limits. The inspections, and 
replacement, if necessary, would be accomplished in accordance with PW 
Alert Service Bulletin (ASB) No. 6038, Revision 3, dated May 8, 1992.
    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 disks that are recoated when complying 
with the inspection requirement of the AD should be zero-timed with 
regard to the next inspection interval. The Federal Aviation 
Administration (FAA) concurs. A paragraph has been added to the 
compliance section that addresses recoated disks.
    One commenter states that there have not been enough disk failures 
to warrant issuance of an AD. The FAA does not concur. The need for an 
AD is based on a determination that an unsafe condition exists that is 
likely to exist in a product of the same type design. That 
determination rests on many factors, including the risk and hazard 
level of the failure mode, which in turn are based on several factors, 
one of which is the number of failures that have occurred. Other data, 
such as inspection data, analytical models, and potential consequences 
are also considered when determining risk and hazard level. The FAA has 
determined in these instances that an unsafe condition exists that is 
likely to exist in engines of the same type design, and, therefore, an 
AD is warranted.
    The FAA received several comments that state that the borescope 
inspection for corrosion assessment of Nickel-Cadmium (NiCad) disks is 
unreliable and can cause unnecessary engine removals. The FAA concurs. 
The borescope inspection for corrosion assessment of NiCad disks has 
been eliminated and only in-shop inspections are now required. In 
addition, high utilization disks require this inspection only at next 
part access.
    The FAA received two comments that state that the four month grace 
period for the records search should be extended. The FAA concurs in 
part. The records search is no longer specifically required, and can be 
replaced by a simple utilization determination and an eddy current 
probe inspection for coating type identification. In addition, the 
utilization determination is based on a fleet or sub-fleet average. The 
AD, however, requires that a utilization determination must be 
conducted for each HPC disk within four months of the effective date of 
this AD for low utilization operations. But, the FAA believes that it 
is now a much simpler task.
    The FAA received several comments that state that the AD does not 
adequately address disks that have been used in both high and low 
utilization operations. The FAA concurs. The utilization rate 
determination now includes an adjustment for disks that have 
experienced mixed utilization rates, and both an initial and a yearly 
recalculation that will account for changes in utilization rate.
    One commenter states that the AD should contain a provision to 
allow for incorporation of the inspection requirements into the 
operator's FAA-approved maintenance program. The FAA does not concur. 
The criticality of the inspections required by the AD require that they 
be separate and distinct from the operator's routine maintenance tasks.
    The FAA received several comments that state that the records 
search and inspection requirements of this AD pose an undue burden on 
operators of PW JT8D engines. The FAA concurs in part. The records 
search is no longer specifically required, and has been replaced by a 
simpler utilization determination together with an eddy current probe 
inspection for coating type identification. In addition, the 
utilization determination is based on a fleet or sub-fleet average. The 
borescope inspection has been eliminated, the disk removal (for 
inspection) requirements have been relaxed based on additional analysis 
and disk inspections, and high utilization disks, fleets, and sub-
fleets will not require a forced engine removal to comply with the AD.
    The FAA received two comments that state that the compliance 
schedule for disk inspections is complex and requires extensive 
recordkeeping. The FAA concurs. The compliance schedule has now been 
simplified by eliminating the borescope inspection and by requiring 
high utilization operators to inspect the disks at the next access 
regardless of coating type.
    The FAA received two comments that state that the issuance of the 
Final Rule should be delayed until additional analytical and 
statistical analyses can be performed to further refine disk fracture 
predictions and required inspection intervals. The FAA does not concur. 
The FAA performed extensive additional analysis since the issuance of 
the proposed rule which has resulted in the revised compliance 
requirements discussed in the FAA's responses to several comments. 
Based on this additional analysis, the FAA believes that the Final Rule 
should not be delayed.
    One commenter states that the cost to drill the borescope hole 
would place an undue burden on the operator. The FAA concurs in part. 
The borescope inspection has been eliminated from the AD and borescope 
access is not specifically required. However, borescope access is 
required if an operator elects to forgo a records search and elects to 
use the eddy current probe to determine coating type.
    One commenter states that the disk records do not always allow for 
identification of the coating. The FAA concurs. The identification of 
disk coating can now be accomplished by use of an eddy current probe.
    One commenter states that the AD should allow for incorporation of 
an engine heater/de-humidifier to be installed on low utilization 
engines when not in operation. This type of device would reduce the 
accumulation of moisture in the engine, which can cause disk corrosion. 
The FAA concurs in part and does not dispute that an engine heater/de-
humidifier would probably reduce the moisture content in low 
utilization engines. This type of device, however, would need to be 
tested to produce data to quantify its effect on moisture and 
associated disk corrosion. Since this data has not been submitted to 
the FAA, it cannot be included in the AD.
    One commenter agreed with the rule as proposed.
    Since publication of the NPRM, the FAA has reviewed and approved 
the technical contents of PW ASB No. 6038, Revision 5, dated August 17, 
1994. This final rule AD references the latest revision of the ASB.
    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 that include 
elimination of the borescope inspection and associated tables, changes 
to the compliance intervals, elimination of the records search, 
addition of the optional eddy current probe inspection, addition of the 
adjustment for mixed utilization, and simplification of the utilization 
determination, are introduced in response to comments received to the 
NPRM. The format of the compliance section is revised to incorporate 
the above changes and to simplify the readability by eliminating 
duplication of compliance instructions that are now included in PW ASB 
6038, Revision 5, dated August 17, 1994. The FAA has determined that 
these changes do not increase the economic burden on any operator, 
however, the economic analysis has been recalculated to reflect the 
total scope of the compliance program. The FAA has also determined that 
the above changes do not compromise the safety impact of the compliance 
program and do not increase the scope of the AD.
    There are approximately 11,119 PW JT8D-1, -1A, -1B, -7, -7A, -7B, -
9, -9A, -11, -15, -15A, -17, -17A, -17R, and -17AR turbofan engines of 
the affected design in the worldwide fleet. The FAA estimates that 
approximately 6,815 engines installed on aircraft of U.S. registry will 
be affected by this AD, and 2 work hours will be necessary to determine 
the utilization rate and type of surface treatment. Based on domestic 
fleet-wide data, the FAA estimates that approximately 8.7% or 593 
engines are considered to have low utilization rates. Approximately 8.6 
work hours will be required to remove these engines from the aircraft, 
500 work hours to tear down, deblade, and to reassemble the engine, and 
8.6 work hours to reinstall the reassembled engines. The FAA estimates 
69% of the removed engines will require scrapping the disks. The FAA 
assumes that three disks per engine may require replacement, and the 
cost of a new disk is approximately $7,000. The average labor rate is 
$55 per work hour. Based on these figures, and a forecast 20-year 
compliance program, the annual cost impact of the AD on U.S. operators 
is estimated to be $1,308,958.
    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. 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:

94-20-01 Pratt & Whitney: Amendment 39-9029. Docket 92-ANE-44.

    Applicability: Pratt & Whitney (PW) JT8D-1, -1A, -1B, -7, -7A, -
7B, -9, -9A, -11, -15, -15A, -17, -17A, -17R, and -17AR turbofan 
engines installed on but not limited to Boeing 737 and 727 series, 
and McDonnell Douglas DC-9 series aircraft.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent fracture of the high pressure compressor (HPC) disks, 
that can result in uncontained release of engine fragments, inflight 
engine shutdown, and airframe damage, accomplish the following:
    (a) Within four months after the effective date of this 
airworthiness directive (AD), determine the fleet and sub-fleet 
average engine utilization rate for the 12 months of operations 
prior to August 17, 1994, the issue date of PW Alert Service 
Bulletin (ASB) No. 6038, Revision 5, in accordance with paragraph 
2.A of PW ASB No. 6038, Revision 5, dated August 17, 1994.
    (1) For fleet or sub-fleet average utilization rates that are 
equal to or greater than 1,300 hours per year, and equal to or 
greater than 900 cycles per year, perform the following:
    (i) For engines or disks that are added to a fleet or subfleet 
after the effective date of this AD, and that were previously 
designated as low utilization disks in accordance with this AD, 
comply with the requirements of paragraph (d) of this AD.
    (ii) Designate all other stage 7 through 12 HPC disks as high 
utilization disks and comply with the requirements of paragraph (b) 
of this AD.
    (2) For fleet or sub-fleet average utilization rates that are 
less than 1,300 hours per year or less than 900 cycles per year, 
within four months after the effective date of this AD, determine 
the initial utilization rate for each stage 7 through 12 HPC disk in 
accordance with paragraph 2.B.(1) of PW ASB No. 6038, Revision 5, 
dated August 17, 1994. Determination of disk utilization in 
accordance with PW ASB No. 6038, Revision 3, dated May 8, 1992, 
constitutes an acceptable alternate method of compliance to 
paragraph (a)(2) of this AD.
    (i) For each HPC stage 7 through 12 disk with an initial 
utilization rate equal to or greater than 1,300 hours per year, and 
equal to or greater than 900 cycles per year, designate this disk as 
a high utilization disk and inspect in accordance with paragraph (c) 
of this AD.
    (ii) For each HPC stage 7 through 12 disk with an initial 
utilization rate less than 1,300 hours per year or less than 900 
cycles per year, designate this disk as a low utilization disk and 
inspect in accordance with paragraph (d) of this AD.
    (iii) For each HPC stage 7 through 12 disk with an unknown 
initial utilization rate, designate this disk as a low utilization 
disk and inspect in accordance with paragraph (d) of this AD.

    Note: Once a disk is designated as low utilization, then it must 
retain this designation for the life of the disk or until recoated.

    (iv) For recoated or new disks, designate this disk as a high 
utilization disk and inspect in accordance with paragraph (c) of 
this AD.
    (b) For high average utilization fleets and sub-fleets, 
excluding those disks identified in paragraph (a)(1)(i) of this AD, 
perform the following for each HPC stage 7 through 12 disk in that 
fleet or sub-fleet:
    (1) Inspect, and recoat or replace if necessary, at the next 
part accessibility of the disk, in accordance with paragraph 
2.D.(1)(b) and Chart A of PW ASB No. 6038, Revision 5, dated August 
17, 1994.
    (2) Recalculate the fleet or sub-fleet average utilization rate 
at 12 month intervals after the previous date of utilization 
determination in accordance with paragraph 2.B of PW ASB No. 6038, 
Revision 5, dated August 17, 1994.
    (i) For fleet or sub-fleet average utilization rates that are 
equal to or greater than 1,300 hours per year, and equal to or 
greater than 900 cycles per year, continue to designate all stage 7 
through 12 HPC disks as high utilization disks and comply with the 
requirements of paragraph (b) of this AD.
    (ii) For fleet or sub-fleet average utilization rates that are 
less than 1,300 hours per year or less than 900 cycles per year, 
within four months of compliance with paragraph (b)(2) of this AD, 
determine the utilization rate for each stage 7 through 12 HPC disk 
in accordance with paragraph 2.B.(1) of PW ASB No. 6038, Revision 5, 
dated August 17, 1994, as follows:
    (A) For each HPC stage 7 through 12 disk with a utilization rate 
equal to or greater than 1,300 hours per year, and equal to or 
greater than 900 cycles per year, designate this disk as a high 
utilization disk and inspect in accordance with paragraph (c) of 
this AD.
    (B) For each HPC stage 7 through 12 disk with a utilization rate 
less than 1,300 hours per year or less than 900 cycles per year, 
designate this disk as a low utilization disk and inspect in 
accordance with paragraph (d) of this AD.
    (C) For each HPC stage 7 through 12 disk with an unknown 
utilization rate, designate this disk as a low utilization disk and 
inspect in accordance with paragraph (d) of this AD.

    Note: Once a disk is designated as low utilization, then it must 
retain this designation for the life of the disk or until recoated.

    (c) For high utilization HPC stage 7 through 12 disks, perform 
the following:
    (1) Inspect, and recoat or replace if necessary, at the next 
part accessibility of the disk, in accordance with paragraph 
2.D.(1)(b) and Chart A of PW ASB No. 6038, Revision 5, dated August 
17, 1994.
    (2) Calculate the disk utilization rate at 12 month intervals 
after the previous date of utilization determination, or after 
installation of new or recoated disks, in accordance with paragraph 
2.B.(3) of PW ASB No. 6038, Revision 5, dated August 17, 1994.
    (i) For HPC stage 7 through 12 disks designated as high 
utilization in accordance with (c)(2), comply with the requirements 
of paragraph (c)(1) of this AD.
    (ii) For HPC stage 7 through 12 disks designated as low 
utilization in accordance with (c)(2), comply with the requirements 
of paragraph (d) of this AD.
    (d) For low utilization HPC stage 7 through 12 disks, perform 
the following:
    (1) Determine the type of disk surface treatment for each HPC 
stage 7 through 12 disk in accordance with paragraph 2.E. of PW ASB 
No. 6038, Revision 5, dated August 17, 1994. Determination of type 
of disk coating in accordance with PW ASB No. 6038, Revision 3, 
dated May 8, 1992, constitutes an acceptable alternate method of 
compliance to paragraph (d)(1) of this AD.
    (2) Inspect, and recoat or remove from service, in accordance 
with paragraph 2.D.(1)(c) and Chart A of PW ASB No. 6038, Revision 
5, dated August 17, 1994.
    (e) For HPC stage 7 through 12 disks that have been recoated in 
accordance with paragraphs (b)(1), (c)(1), or (d)(2) of this AD, 
designate these disks as high utilization and perform the following:
    (1) For disks installed in an engine that is part of a high 
utilization fleet, comply with the requirements of paragraph (b) of 
this AD.
    (2) For disks installed in an engine that is part of a low 
utilization fleet, comply with the requirements of paragraph (c) of 
this AD.
    (f) For the purpose of this AD, recoat of an HPC disk is defined 
as removal and application of new plating or coating in accordance 
with Sections 72-36-41, Repair 02, 72-36-42, Repair 02, 72-36-43, 
Repair 03, 72-36-44, Repair 03, 72-36-45, Repair 03, 72-36-46, 
Repair 03, as applicable, of PW JT8D Engine Manual P/N 481672.
    (g) For the purpose of this AD, part accessibility is defined as 
the removal of the disk from the engine and deblading of that disk.
    (h) For the purpose of this AD, a sub-fleet is defined as any 
individual aircraft or any portion of an operators fleet that 
operates in a separate and unique route structure, characterized by 
different flight lengths, frequencies, or geographic location.
    (i) 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.

    (j) 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.
    (k) The inspections, and replacement or recoating if necessary, 
shall be done in accordance with the following service document: 

------------------------------------------------------------------------
    Document No.         Pages        Revision             Date         
------------------------------------------------------------------------
PW ASB No. 6038....          1     5.............  August 17, 1994.     
                             2     Original......  August 5, 1991.      
                             3     5.............  August 17, 1994.     
                           4-6     4.............  July 13, 1994.       
                          7-26     5.............  August 17, 1994.     
Appendix A.........      27-41     5.............  August 17, 1994.     
Appendix B NDIP-803       1-33     4.............  July 13, 1994.       
Appendix to NDIP-          1-2     4.............  July 13, 1994.       
 803.                                                                   
      Total Pages:                                                      
       76.                                                              
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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, Publications 
Department, 400 Main Street, East Hartford, Connecticut 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.
    (l) This amendment becomes effective on November 28, 1994.

    Issued in Burlington, Massachusetts, on September 15, 1994.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification 
Service.

[FR Doc. 94-23326 Filed 9-26-94; 8:45 am]

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