AD 94-15-16

This amendment adopts a new airworthiness directive (AD), applicable to Pratt & Whitney JT9D series turbofan engines, that requires a one-time modification and overhaul of engine control system accessories. This amendment is prompted by multiple engine surge and power loss events caused by deterioration of internal components of engine control system accessories. The actions specified by this AD are intended to prevent the loss of engine compressor surge margin caused by the deterioration of engine control system accessories, resulting in an engine surge, and subsequent power loss or inflight engine shutdown.

Final rule.

94-15-16 Pratt & Whitney: Amendment 39-8987. Docket 91-ANE-51.
Applicability: Pratt & Whitney (PW) Model JT9D-3A, -7, -7A, -7AH, -7H, -7F, -7J, -20, -20J, -59A, -70A, and -7Q turbofan engines installed on but not limited to Boeing 747 series, McDonnell Douglas DC-10 series, and Airbus A300 series aircraft.
Compliance: Required as indicated, unless accomplished previously.
To prevent the loss of engine compressor surge margin caused by the deterioration of engine control system accessories, resulting in an engine surge, and subsequent power loss or inflight engine shutdown, accomplish the following:
(a) Perform a one-time overhaul and modification of the main fuel controls as follows:
(1) For main fuel controls with either 12,000 hours or more time since overhaul (TSO) on the effective date of this AD or with an undocumented TSO, or for those main fuel controls that have never been overhauled and have either 12,000 hours or more time since new (TSN) on the effectivedate of this AD or an undocumented TSN, overhaul in accordance with the applicable Hamilton Standard (HS) Maintenance Manual (MM) listed in Table 1 of this AD, and modify in accordance with the applicable HS Service Bulletins (SB) listed in Table 2 of this AD, at the earliest of: the next shop visit; 3,000 hours time in service (TIS) after the effective date of this AD; or July 31, 1995.
(2) For main fuel controls with more than 10,000 hours but less than 12,000 hours TSO, or TSN if never overhauled, on the effective date of this AD, overhaul in accordance with the applicable HS MM listed in Table 1 of this AD, and modify in accordance with the applicable HS SB's listed in Table 2 of this AD, not later than 3,000 hours TIS after the effective date of this AD, or by July 31, 1995, whichever occurs first.
(3) For main fuel controls with 10,000 hours or less TSO, or TSN if never overhauled, on the effective date of this AD, overhaul in accordance with the applicable HS MM listedin Table 1 of this AD, not later than 12,000 hours TSO or TSN, or by July 31, 1995, whichever occurs later.
(4) For main fuel controls with 10,000 hours or less TSO, or TSN if never overhauled, on the effective date of this AD, modify in accordance with the applicable HS SB's listed in Table 2 of this AD, not later than 12,000 hours TSO or TSN, or by July 31, 1995, whichever occurs first.

Table 1, ENGINE ACCESSORY OVERHAUL REFERENCE LIST

ACCESSORY DESCRIPTION
HAMILTON STANDARD
MAINT. MANUAL NO.
TEMPORARY REVISION NO.
Main fuel controls: JFC68-3
73-21-01, Revision 19,
dated January 15, 1992
73-54,
dated June 15, 1992
JFC68-4
73-21-02, Revision 10,
dated January 15, 1992
73-31,
dated June 15, 1992
JFC68-6
73-21-03, Revision 10,
dated September 15, 1992
N/A
Engine vane controls:

EVC3-2 and EVC3-4
75-31-01, Revision 20,
dated July 1, 1992
75-26,
dated July 15, 1993
EVC3-5
75-32-01, Revision 9,
dated June 15, 1986
75-5, dated July 1, 1992
Engine vane and bleed controls:

GTA9-1 and GTA9-2
75-34-01, Revision 11,
dated August 15, 1992
N/A

Table 2, HAMILTON STANDARD MAIN FUEL CONTROL UNIT (FCU) SERVICE BULLETIN INCORPORATION LIST

FCU MODEL JFC68-3, JT9D-3A, -7 SERIES ENGINES
FCU MODEL JFC68-4, JT9D-20, -20J SERIES ENGINES
FCU MODEL JFC68-6 JT9D-59A, -70A, -7Q SERIES ENGINES
73-150 (L160), Revision 1,
dated 8-15-91.
73-50 (L94), Revision 2,
dated 12-13-93
73-23 (L30), Revision 1, dated 8-15-91
73-139 (L152), Original, dated 2-27-76
73-42 (L87), Original, dated 2-27-76.
N/A
73-129 (L143), Revision 3, dated 7-1-77.
73-36 (L81), Revision 3, dated 7-1-77.
73-3 (L14), Original, dated 1-7-77.
73-128 (L142), Revision 1, dated 8-29-75
73-35 (L80), Revision 1, dated 8-29-75.
N/A
73-127 (L141), Revision 2, dated 10-31-78.
73-33 (L79), Revision 2, dated 10-31-78.
N/A
73-122 (L137), Revision 1, dated 9-27-77.
73-29 (L75), Revision 1, dated 9-27-77.
N/A
73-121 (L136), Original, dated 5-29-74
73-28 (L74), Original, dated 5-29-74
N/A
73-117 (L133), Revision 3, dated 10-15-74.
73-24 (L71), Revision 2, dated 10-15-74.
N/A
73-111 (L128), Revision 1, dated 10-27-76.
73-21 (L69), Revision 1, dated 10-27-76.
N/A
N/A
N/A
73-27 (L33), Revision 1, dated 9-27-82.
73-19, General, Revision 1, dated 9-20-86.
73-19, General, Revision 1, dated 9-20-86.
73-19, General, Revision 1, dated 9-20-86.
(b) Perform a one-time overhaul and modification of engine vane controls as follows:
(1) For engine vane controls with either 12,000 hours or more TSO on the effective date of this AD or with an undocumented TSO, or for those engine vane controls that have never been overhauled and have either 12,000 hours or more TSN on the effective date of this AD or an undocumented TSN, overhaul in accordance with the applicable HS MM listed in Table 1 of this AD, and modify in accordance with the applicable HS SB's listed in Table 3 of this AD, at the earliest of: the nextshop visit; 3,000 hours time in service (TIS) after the effective date of this AD; or July 31, 1995.
(2) For engine vane controls with more than 10,000 hours but less than 12,000 hours TSO, or TSN if never overhauled, on the effective date of this AD, overhaul in accordance with the applicable HS MM listed in Table 1 of this AD, and modify in accordance with the applicable HS SB's listed in Table 3 of this AD, not later than 3,000 hours TIS after the effective date of this AD, or by July 31, 1995, whichever occurs first.
(3) For engine vane controls with 10,000 hours or less TSO, or TSN if never overhauled, on the effective date of this AD, overhaul in accordance with the applicable HS MM listed in Table 1 of this AD, not later than 12,000 hours TSO or TSN, or by July 31, 1995, whichever occurs later.
(4) For engine vane controls with 10,000 hours or less TSO, or TSN if never overhauled, on the effective date of this AD, modify in accordance with the applicable HS SB's listed in Table 3 of this AD not later than 12,000 hours TSO or TSN, or by July 31, 1995, whichever occurs first.

Table 3
HAMILTON STANDARD ENGINE VANE CONTROL (EVC) RECOMMENDED SERVICE BULLETIN INCORPORATION LIST

EVC3-2 MODEL
JT9D-3A, -7
SERIES ENGINES
EVC3-4 MODEL JT9D-20, -20J
SERIES ENGINES
EVC3-5 MODEL
JT9D-59A, -70A
SERIES ENGINES
75-48 (L46), Revision 1,
dated 8-6-91.
75-27 (L33), Revision 1,
dated 8-19-91.
75-9 (L10), Revision 1,
dated 8-21-91.
75-45 (L43), Revision 1,
dated 8-16-91.
75-24 (L30), Revision 1,
dated 8-19-91
75-6 (L7), Revision 1,
dated 8-20-91.
75-43 (L42), Revision 2,
dated 4-25-91
75-23 (L29), Original,
dated 3-31-88.
75-5, Original,
dated 3-31-88
75-41 (L41), Revision 3,
dated 8-16-91.
75-22 (L28), Revision 1,
dated 8-19-91
75-4 (L5), Revision 2,
dated 8-20-91.
75-42, Revision 1,
dated 8-16-91.
N/A
N/A
75-37 (L40), Revision 3,
dated 8-16-91.
75-19 (L27), Revision 3,
dated 8-19-91.
75-2 (L4), Revision 1,dated 11-8-79.
75-36, Revision 1,
dated 9-1-78.
75-20, Original,
dated 9-1-78.
N/A
75-31 (L35), Original,
dated 5-23-75.
75-14 (L22), Original,
dated 5-23-75.
N/A
75-28 (L33), Original,
dated 1-3-75.
75-11 (L20), Original,
dated 1-3-75.
N/A
75-27 (L32), Original,
dated 9-10-74.
75-10 (L19), Original,
dated 9-10-74.
N/A
75-49 (L47), Original,
dated 5-13-91.
75-28 (L34, Original,
dated 5-13-91.
N/A
(c) Perform a one-time overhaul and modification of engine vane and bleed controls as follows:
(1) For engine vane and bleed controls with either 10,000 hours or more TSO on the effective date of this AD or with an undocumented TSO, or for those engine vane and bleed controls that have never been overhauled and have either 10,000 hours or more TSN on the effective date of this AD or an undocumented TSN, overhaul in accordance with the applicable HS MM listed in Table 1 of this AD, and modify in accordance with the applicable HS SB's listed inTable 4 of this AD, at the earliest of: the next shop visit; 3,000 hours TIS after the effective date of this AD; or July 31, 1995.
(2) For engine vane and bleed controls with more than 8,000 hours but less than 10,000 hours TSO, or TSN if never overhauled, on the effective date of this AD, overhaul in accordance with the applicable HS MM listed in Table 1 of this AD, and modify in accordance with the applicable HS SB's listed in Table 4 of this AD, not later than 3,000 hours TIS after the effective date of this AD, or by July 31, 1995, whichever occurs first.
(3) For engine vane and bleed controls with 8,000 hours or less TSO, or TSN if never overhauled, on the effective date of this AD, overhaul in accordance with the applicable HS MM listed in Table 1 of this AD, not later than 10,000 hours TSO or TSN, or by July 31, 1995, whichever occurs later.
(4) For engine vane and bleed controls with 8,000 hours or less TSO, or TSN if never overhauled, on the effective date of this AD, modify in accordance with the applicable HS SB's listed in Table 4 of this AD, not later than 10,000 hours TSO or TSN, or by July 31, 1995, whichever occurs first.

Table 4
HAMILTON STANDARD ENGINE VANE BLEED CONTROL (EVBC) (GTA9) REQUIRED SERVICE BULLETIN INCORPORATION LIST
JT9D-59A, -70A, -7Q, SERIES ENGINES

Service Bulletin
Revision
Date
GTA9-75-26 (L21)
1
8-21-91
GTA9-75-19 (L14)
1
8-21-91
GTA9-75-17 (L13)
Original
3-31-88
GTA9-75-16 (L12)
Original
3-20-88
GTA9-75-9 (L8)
3
8-15-92

(d) Perform a one-time overhaul and modification of main fuel gear pumps as follows:
(1) For main fuel gear pumps with either 8,000 hours or more TSO on the effective date of this AD or with an undocumented TSO, or for those main fuel gear pumps that have never been overhauled and have either 8,000 hours or more TSN on the effective date of this AD or an undocumented TSN, overhaul in accordance with either Argo-Tech (AT) Overhaul Manual (OM) No. 73-11-01 orNo. 73-11-02, as applicable, and modify in accordance with the applicable TRW, AT, and Pratt & Whitney (PW) SB's listed in Table 5 of this AD, at the earliest of: the next shop visit; 3,000 hours TIS after the effective date of this AD; or July 31, 1995.
(2) For main fuel gear pumps with more than 6,000 hours but less than 8,000 hours TSO, or TSN if never overhauled, on the effective date of this AD, overhaul in accordance with either AT OM No. 73-11-01 or No. 73-11-02, as applicable, and modify in accordance with the applicable TRW, AT, and PW SB's listed in Table 5 of this AD, not later than 3,000 hours TIS after the effective date of this AD, or by July 31, 1995, whichever occurs first.
(3) For main fuel gear pumps with 6,000 hours or less TSO, or TSN if never overhauled, on the effective date of this AD, overhaul in accordance with either AT OM No. 73-11-01 or No. 73-11-02, as applicable, not later than 8,000 hours TSO or TSN, or by July 31, 1995, whichever occurs later.(4) For main fuel gear pumps with 6,000 hours or less TSO, or TSN if never overhauled, on the effective date of this AD, modify in accordance with the applicable TRW, AT and PW SB's listed in Table 5 of this AD, not later than 8,000 hours TSO or TSN, or by July 31, 1995, whichever occurs first.

Table 5
TRW, AT, AND PW MAIN FUEL GEAR PUMP REQUIRED SERVICE BULLETIN INCORPORATION LIST

JT9D-3A, -7, -20, -20J , SERIES ENGINES
TRW 73-28 (-26), Revision 2, dated 4-15-77.
JT9D-59A, -70A, -7Q, SERIES ENGINES
N/A
TRW 73-29 (-27), Revision 1, dated 9-1-80.
TRW 73-5 (-9), Original, dated 4-30-81.
TRW 73-31 (-29), Original, dated 9-1-79.
N/A
TRW 73-32 (-30), Revision 3, dated 4-1-85.
N/A
AT 73-36 (-32), Revision 1, dated 10-1-88.
N/A
AT 73-43, Original, dated 12-15-89.
N/A
N/A
TRW 73-8 (-12) Original, dated 9-1-82.
PW 5889, Revision 6, dated 12-20-93.
N/A
PW 6127, Original, dated 9-10-93.
N/A

(e) For the purpose of this AD, a shop visit is definedas an engine removal where engine maintenance entails separation of pairs of mating engine flanges or the removal of a disk, hub, or spool.
(f) 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 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.
(g) 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.
(h) The overhauls and modifications shall be done in accordance with the following service bulletins:

SB NO.
PAGES
REVISION
DATE
TRW SB No. 73-28

Total Pages: 10
1
2
3
4
4A
5-7
8
9-10
2
1
2
1
2
1
2
1
4-15-77
1-15-77
4-15-77
1-15-77
4-15-77
1-15-77
4-15-77
1-15-77
TRW SB No. 73-29

Total Pages: 4
1
2
3
4
1
Original
1
Original
9-1-80
3-1-79
9-1-80
3-1-79
TRW SB No. 73-31
Total Pages: 3
1-3
Original
9-1-79
TRW SB No. 73-32
Total Pages: 4
1-3
4
3
1
4-1-85
6-15-81
Argo-Tech
SB No. 73-36
Total Pages: 3
1-3
1
10-1-88
Argo-Tech
SB No. 73-43
Total Pages: 4
1
Original
12-15-89
TRW SB No. 73-8
Total Pages: 4
1-4
Original
9-1-82
TRW SB No. 73-5
Total Pages: 3
1-3
Original
4-30-81
PW SB No. 5889

Total Pages: 20
1
2
3-5
6
7-8
9-11
12
13
14-18
19
20
6
5
Original
4
Original
3
1
4
Original
6
4
12-20-93
9-21-92
12-21-89
5-7-92
12-21-89
10-4-91
1-24-90
5-7-92
12-21-89
12-20-93
5-7-92
PW SB No.6127
Total Pages: 14
1-14
Original
9-10-93
HS SB No.
GTA9-75-26
Total Pages: 6
1-3
4-6
1
Original
8-21-91
5-9-90
HS SB No.
GTA9-75-17
Total Pages: 3
1-3
Original
3-31-88
HS SB No.
GTA9-75-16
Total Pages: 3
1-3
Original
3-20-88
HS SB No.
GTA9-75-9
Total Pages: 7
1-2
3-7
3
2
8-15-92
8-21-91
HS SB No. 75-9

Total Pages: 7
1-2
2A/2B
3-6
1
1
Original
8-20-91
8-20-91
5-9-90
HS SB No. 75-6
Total Pages: 3
1-3
1
8-20-91
HS SB No. 75-5
Total Pages: 3
1-3
Original
3-31-88
HS SB No. 75-4
Total Pages: 7
1-3
4-7
2
1
8-20-91
10-15-84
HS SB No. 75-2
Total Pages: 7
1-7
1
11-8-79
HS SB No. 75-28
Total Pages: 4
1-4
Original
5-13-91
HS SB No. 75-27
Total Pages: 5
1-6
Original
8-19-91
HS SB No. 75-24
Total Pages: 3
1-3
1
8-19-91
HS SB No. 75-23
Total Pages: 3
1-3
Original
3-31-88
HS SB No. 75-22

Total Pages: 6
1-2
2A/2B
3-6
1
1
Original
8-19-91
8-19-91
4-30-84
HS SBNo. 75-19

Total Pages: 7
1-2
2A/2B
3-7
3
3
2
8-19-91
8-19-91
11-8-79
HS SB No. 75-20
Total Pages: 3
1-3
Original
9-1-78
HS SB No. 75-14
Total Pages: 4
1-4
Original
5-23-75
HS SB No. 75-11
Total Pages: 3
1-3
Original
1-3-75
HS SB No. 75-10
Total Pages: 5
1-5
Original
9-10-74
HS SB No. 75-49
Total Pages: 4
1-4
Original
5-13-91
HS SB No. 75-48
Total Pages: 6
1-2
3-6
1
Original
8-16-91
5-9-90
HS SB No. 75-45
Total Pages: 4
1-4
1
8-16-91
HS SB No. 75-43
Total Pages: 4
1-4
2
4-25-91
HS SB No. 75-42
Total Pages: 2
1-2
1
8-16-91
HS SB No. 75-41
Total Pages: 7
1-3
4-7
3
2
8-16-91
12-20-90
HS SB No. 75-37

Total Pages: 8
1-2
2A/2B
3-7
3
3
2
8-16-91
8-16-91
12-12-79
HS SB No. 75-36
Total Pages: 3
1-3
Revision 1
9-1-78
HS SB No. 75-31
Total Pages: 4
1-4
Original
5-23-75
HS SB No. 75-28
Total Pages: 3
1-3
Original
1-3-75
HS SB No. 75-27
Total Pages: 6
1-5
Original9-10-74
HS General SB No.
73-19
Total Pages: 6
1-3
4
5-6
1
Original
1
9-20-86
12-15-84
9-20-86
HS SB No. 73-27

Total Pages: 5
1-2
3-4
5
1
Original
1
9-27-82
2-10-82
9-27-82
HS SB No. 73-23

Total Pages: 5
1-2
2A/2B
3-5
1
1
Original
8-15-91
8-15-91
4-30-81
HS SB No. 73-3
Total Pages: 5
1-5
Original
1-7-77
HS SB No. 73-50

Total Pages: 5
1-2
2A/2B
3
4-5
2
1
Original
2
12-13-92
8-15-91
4-30-81
12-13-92
HS SB No. 73-42
Total Pages: 3
1-3
Original
2-27-76
HS SB No. 73-36

Total Pages: 5
1
2
3
4
5
3
1
3
2
3
7-1-77
11-5-76
7-1-77
4-20-77
7-1-77
HS SB No. 73-35

Total Pages: 7
1-2
3-4
5-6
7
1
Original
1
Original
8-29-75
4-22-75
8-29-75
4-22-75
HS SB No. 73-33

Total Pages: 5
1
2
3-4
5
2
1
2
1
10-31-78
3-5-76
10-31-78
3-5-76
HS SB No. 73-29

Total Pages: 7
1-3
4-5
6-7
1
Original
1
9-27-77
2-7-75
9-27-77
HS SB No. 73-28
Total Pages: 5
1-5
Original
5-29-74
HS SB No. 73-24
Total Pages: 5
1-2
3-5
2
Original
10-15-74
11-16-73
HS SB No. 73-21
Total Pages: 8
1-8
1
10-27-76
HS SB No. 73-150
Total Pages: 5
1-2B
3-5
1
Original
8-15-91
4-30-81
HS SB No. 73-139
Total Pages: 3

1-3
Original
2-27-76
HS SB No. 73-129

Total Pages: 5
1
2
3
4
5
3
Original
3
2
3
7-1-77
2-21-75
7-1-77
4-20-77
7-1-77
HS SB No. 73-128

Total Pages: 7
1-3
4
5
6-7
1
Original
1
Original
8-29-75
4-22-75
8-29-75
4-22-75
HS SB No. 73-127

Total Pages: 6
1
2
3-6
2
Original
2
10-31-78
3-12-75
10-31-78
HS SB No. 73-122

Total Pages: 7
1
2
3
4-5
6-7
1
Original
1
Original
1
9-27-77
2-7-75
9-27-77
2-7-75
9-27-77
HS SB No. 73-121
Total Pages: 5
1-5

Original

5-29-74

HS SB No. 73-117
Total Pages: 5
1-2
3-5
3
Original
10-15-74
11-16-73
HS SB No. 73-111
Total Pages: 8
1-8
1
10-27-76

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, Technical Publications Department, M/S 132-30, 400 Main Street, East Hartford, CT 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.
(i) This amendment becomes effective on October 14, 1994.

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 January 5, 1993 (58 FR 275). That action proposed to require a one-time modification and overhaul of engine control system accessories to prevent loss of engine compressor surge margin caused by the deterioration of engine control system accessories, resulting in an engine surge, and subsequent power loss or inflight engine shutdown.
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.
Several commenters question the need for the Federal Aviation Administration (FAA) to issue an AD to improve the inflight engine shutdown rate. The commenters cite section 39.1 of the Federal Aviation Regulations (14 CFR 39.1) which requires that an AD be issued when an unsafe condition exists in a product and is likely to exist or develop in other products of the same design. The commenters further state that an inflight engine shutdown on a multi-engine aircraft is not a safety event but an operational restriction. The FAA does not concur. A decrease in engine component reliability can pose a potentially unsafe condition due to excessive inflight engine shutdown or surge rates. After a review of the inflight engine shutdown and surge rates, the FAA determined that certain populations of engines had a heightened susceptibility to engine surge, but in many instances engine surge events did not result in an actual inflight engine shutdown. For this reason it is not sufficient to consider only inflight engine shutdown rates. Other measures of overall engine reliability were also considered, including component mean time between failure and unscheduled removal rates. The requirements of this AD will help preclude an incident where multiple engines on the same aircraft surge, with or without a resultant inflight engine shutdown. The FAA has received 12 reports of multiple engine surge events occurring during critical phases of flight such as takeoff and climb-out; therefore, the FAA has determined that an unsafe condition exists in a product that is likely to exist or develop in other products of the same type design and, accordingly, AD action is warranted.
One commenter states that the AD should be revised to require incorporation of its provisions into an operator's existing FAA-approved maintenance program, and that once incorporated into the program, the AD would no longer be applicable. In addition, the commenter suggests that the FAA Flight Standards District Offices should administer the maintenance program. The FAA does not concur. This AD will restore engine component reliability through incorporation of certain design upgrades. These upgrades are necessary due to design deficiencies of these components. This AD will not require periodic maintenance, but only a one-time incorporation of certain service bulletin (SB) upgrades. The FAA has, however, approved guidance titled, "Guidance Criteria for Overhaul," which is incorporated as a separate document into the latest revisions to the components' maintenance manuals (MM). This document essentially provides for incorporation of the SB's required by this AD, and also requires replacement of all disposable packings and seals. The guidance provides suggested maintenance intervals consistent with mean time between failure rates for each component.
Several commenters request as an alternate means of compliance to the modification required by PW SB No. 5889, that the FAA include in this AD the tap and torque procedure described in the applicable engine MM. The FAA does not concur. The tap and torque procedure has not provided consistent fault-proof installation of engine main fuel pumps. Revision 6 toPW SB No. 5889 introduces the improved QAD ring with the necessary featural changes to alleviate the possibility of a maintenance-induced error during the installation of an engine main fuel pump. The FAA has incorporated Revision 6 into this AD.
One commenter states that rather than specifying "Time Since Last Overhaul" the AD should read "Time Since Limited Overhaul." The FAA does not concur. The intervals specified in this AD are based on time since a complete overhaul accomplished in accordance with the components' MM. Previous revisions to the components' MM's did not include a defined procedure for limited overhaul. Therefore, there is no standard by which the FAA can evaluate whether the limited overhaul procedures will accomplish the necessary design upgrades, and the commenter does not include supporting data. The latest revisions to the components' MM's, in the section titled "Guidance Criteria for Overhaul," defines what is required to perform a limited overhaul on these components. If an operator satisfies these minimum criteria and has data to demonstrate low inflight engine shutdown and surge rates, the operator may apply for an alternate means of compliance with this AD.
One commenter states that Hamilton Standard (HS) SB No. JFC68 73-19 should be referred to as a "General" SB in order to avoid confusion. The FAA concurs and the final rule has been changed accordingly.
One commenter states that HS SB No. JFC68-3 73-150 requires installation of components that are then replaced during accomplishment of HS SB No. JFC68-3 73-151, and that HS SB No. JFC68-4 73-50 requires installation of components that are then replaced during accomplishment of HS SB No. JFC68-4 73-51. The commenter questions if it is acceptable to install the most recent parts. The FAA concurs. The reliability aspects of the requirements of HS SB No. JFC68-3 73-150 and HS SB No. JFC68-3 73-151, and HS SB No. JFC68-4 73-50 and HS SB No. JFC68-4 73-51, are similar. Accomplishment of HS SB No. JFC68-3 73-151 and HS SB No. JFC68-4 73-51 in lieu of HS SB No. JFC68-3 73-150 and HS SB No. JFC68-4 73-50, respectively, constitute an acceptable alternate means of compliance for this AD.
One commenter states that HS MM 73-21-01, Revision 19, is dated January 15, 1992, not June 15, 1991. The FAA concurs and has changed the AD accordingly.
One commenter states that HS SB No. 75-49 requires components to be reidentified to L47, not L30. The FAA concurs and has changed the AD accordingly.
One commenter states that HS SB No. 75-27 has not been revised. The FAA concurs and has changed the AD accordingly.
Several commenters address that HS Engine Vane Control (EVC)3-5 is not applicable to the PW Model JT9D-7Q engine. The FAA concurs and has changed the AD accordingly.
Several commenters state that TRW (formerly Argo-Tech) SB 73-43 does not include the PW Models JT9D-20 or -20J engines and question if compliance will be required for these models.The FAA concurs. PW has released SB No. 6127, dated September 10, 1993, that includes the PW JT9D-20 and -20J engine models. This SB in turn makes reference to Argo-Tech SB No. 73-43, which calls for modification of the PW Models JT9D-20 and -20J fuel pump to accommodate the new QAD ring. The FAA has changed the AD accordingly to include this SB.
One commenter states that soft-time requirements would be preferable to hard time requirements for one-time overhaul and modification of engine accessories. The FAA does not concur. Most significantly, many operators have decided to postpone accessory upgrades recommended by PW. The FAA's analysis indicates that postponing these upgrades has a cumulative effect which has resulted in a degradation of component reliability and loss of engine surge margin. The FAA conducted an industry-wide survey and determined that there is a direct correlation between accessory build standard and engine surge rate. There is also a direct correlation between time between accessory overhaul and loss of engine surge margin due to the degradation of the accessories. The one-time overhaul and modifications required by this AD have been established based on the FAA's review of inflight engine shutdown and surge rates. The FAA recommends that following accomplishment of the one-time overhaul and modifications required by this AD, all operators establish a soft-time overhaul interval for maintenance of engine accessories in accordance with the "Guidance Criteria for Overhaul" incorporated into the components' MM's.
One commenter states that the AD does not clearly state that the overhaul requirement for the accessories is a one-time overhaul. The FAA concurs and has changed the AD accordingly to emphasize that this overhaul is a one-time requirement only.
One commenter questions why the threshold for overhaul is 12,000 hours time in service (TIS) for the EVC and 10,000 hours for the Engine Vane and Bleed Control (EVBC). The commenter states that the EVBC is more reliable than the EVC. The FAA does not concur. The fleet survey provided data on mean time failure rates from which the overhaul intervals specified in this AD were derived. Based on this review, the FAA has determined that maximum time between overhauls should be 12,000 hours TIS for EVC's and 10,000 hours TIS for EVBC's. If an operator can provide enhanced reliability data through improved maintenance procedures, the FAA may consider this data as an acceptable alternate means of compliance for this AD.
One commenter states that the AD does not account for operators' responsiveness to vendor recommended modifications and that the AD requires immediate incorporation of SB's assigned a low to medium priority by the Original Equipment Manufacturer. The FAA does not concur. The FAA conducted a fleet survey which showed that most operators lacked adequate accessory build standards and that this inadequacy had a direct effect on engine surge and inflight shutdown rates. Furthermore, those operators that have incorporated the modifications required by this AD, satisfy
the intent of this AD, and no further action is required. Regarding the SB's priority, the FAA has determined that all the required SB's have a significant effect on engine surge margin regardless of SB category.
One commenter states that the AD is contradictory about previous accomplishment. The commenter references paragraphs (a)(3), (a)(4), (b)(3), (b)(4), (c)(3), (c)(4) of the AD. The FAA does not concur. These paragraphs state that previous accomplishment for overhaul is based on Time Since Overhaul, and extend credit to those operators who have already accomplished overhaul provided they are within the prescribed intervals specified by the AD. As to the paragraphs requiring modifications, if the operator has implemented all the SB's referenced in the AD, then the operator has accomplished previously the modification requirements of this AD.
One commenter states that the AD will require all their components to be overhauled and modified by the calendar end date of January 31, 1995, based on the operator's maintenance program, which will require overhaul of all components disassembled to the extent required for these modifications. The FAA does not concur. An individual operator's FAA-approved maintenance program may dictate that the components must be overhauled by a certain date, but for other operators there may be instances where certain components may remain in service past the calendar-end date. In the NPRM, paragraphs (a)(3), (b)(3), (c)(3), and (d)(3) stated that certain components must be overhauled prior to a certain TIS, or January 31, 1995, whichever occurs later. Since publication of that NPRM, the FAA has determined to extend the compliance end date to July 31, 1995, due to the time required to adequately address all comments and publish the final rule.
One commenter states that the AD would require, based on current aircraft utilization, the majority of Fuel Control Units to be modified within 250 days after the effective date of this AD. The FAA concurs. The FAA has determined that the drawdown intervals defined in this AD constitute an acceptable minimum standard of airworthiness for the PW JT9D fuel control.
One commenter states that monitoring of engine condition is not taken into account as a compliance option in the AD. The FAA concurs. However, this data could be used as substantiation for an alternate means of compliance.
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 FAA estimates that approximately 300 engines of the affected design installed on aircraft of U.S. registry will be affected by this AD, that it will take approximately 30 work hours per engine to accomplish the required actions, and that the average labor rate is $55 per work hour. Required parts will cost approximately $13,100 per engine. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $4,425,000.
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 activity" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policiesand 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. 39.13 - [AMENDED]
2. Section 39.13 is amended by adding the following new airworthiness directive: