[Federal Register Volume 59, Number 21 (Tuesday, February 1, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-346]


[[Page Unknown]]

[Federal Register: February 1, 1994]


-----------------------------------------------------------------------


DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 92-NM-173-AD; Amendment 39-8792; AD 94-01-10]

 

Airworthiness Directives; Boeing Model 757 Series Airplanes 
Equipped With Pratt and Whitney PW2000 Series Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: This amendment supersedes an existing airworthiness directive 
(AD), applicable to certain Boeing Model 757 series airplanes, that 
currently requires inspections, adjustments, and functional checks of 
the engine thrust reverser system; and modification of the engine 
thrust reverser directional control valve. This amendment adds a 
requirement for installation of an additional thrust reverser system 
locking feature; revises the compliance time for accomplishing the 
modification; adds airplanes to the applicability; and requires 
periodic functional tests of the locking feature following its 
installation. This amendment is prompted by results of a safety review 
of the thrust reverser system on these airplanes. The actions specified 
by this AD are intended to prevent deployment of a thrust reverser in 
flight and subsequent reduced controllability of the airplane.

DATES: Effective March 3, 1994.
    The incorporation by reference of Boeing Service Bulletin 757-78-
0028, Revision 1, dated October 29, 1992, and Boeing Service Bulletin 
757-78-0028, Revision 2, dated January 14, 1993, as listed in the 
regulations, is approved by the Director of the Federal Register as of 
March 3, 1994.
    The incorporation by reference of certain other publications listed 
in the regulations was approved previously by the Director of the 
Federal Register as of September 16, 1991 (56 FR 46725, September 16, 
1991).

ADDRESSES: The service information referenced in this AD may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the Federal 
Aviation Administration (FAA), Transport Airplane Directorate, Rules 
Docket, 1601 Lind Avenue SW., Renton, Washington; or at the Office of 
the Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.

FOR FURTHER INFORMATION CONTACT: Jeffrey Duven, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (206) 227-2688; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations by superseding AD 91-20-09, Amendment 39-8043 (56 
FR 46725, September 16, 1991), which is applicable to certain Boeing 
Model 757 series airplanes equipped with Pratt and Whitney PW2000 
series engines, was published as a supplemental notice of proposed 
rulemaking (NPRM) in the Federal Register on August 6, 1993 (58 FR 
42034). The action proposed to require certain inspections, 
adjustments, and functional checks of the engine thrust reverser 
system; modification of the engine thrust reverser directional control 
valve; installation of an additional thrust reverser system locking 
feature (sync lock); and periodic functional tests of the locking 
feature following its installation.
    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 supports the proposed rule.
    One commenter requests that paragraph (e) of the proposed rule be 
revised to require only the ``sync lock test'' portion of the proposed 
functional test. The commenter indicates that the proposed ``Thrust 
Reverser Auto Restow and Sync Lock Test'' is a combination test 
procedure that consists of an auto restow test of the entire thrust 
reverser assembly and a test of the sync lock mechanism. The commenter 
believes that this combination test procedure is more extensive than 
that which is necessary to verify proper functioning of the sync lock.
    The FAA concurs with the commenter's request. The FAA's objective 
in proposing periodic functional tests of the sync lock device is to 
ensure the integrity of the locking function. The FAA included the auto 
restow portion of the functional test in the proposal because the 
airplane maintenance manual does not distinguish between the sync lock 
test and the auto restow test. However, since issuance of the proposal, 
Boeing has submitted to the FAA separate procedures for accomplishment 
of the sync lock integrity test described in the airplane maintenance 
manual. These procedures are accomplished independently of the auto 
restow test and other thrust reverser system tests. Accordingly, the 
FAA has revised paragraph (e) of the final rule to remove the 
requirement to accomplish the auto restow portion of the functional 
test and to specify instructions for accomplishment of the sync lock 
integrity test only.
    The Air Transport Association (ATA) of America, on behalf of 
several of its members, requests that the FAA review its justification 
for including in an AD the functional test requirements proposed in 
paragraph (e). ATA members are not opposed to accomplishing the 
proposed tests as part of their maintenance programs, but are opposed 
to accomplishing the tests as part of the requirements of this AD. The 
commenters believe that the adoption of paragraph (e), as proposed, is 
equivalent to issuing a Certification Maintenance Requirements (CMR) 
item by means of an AD.
    The FAA does not concur. The FAA acknowledges that similarities 
exist between the periodic functional tests of the sync lock, as 
required by paragraph (e) of this AD, and tasks denoted as CMR items. 
The extent of those similarities is that both CMR items and the 
periodic functional tests required by this AD place specific 
requirements on operators of Model 757 series airplanes with respect to 
scheduling airplane maintenance activities.
    Generally, CMR items define specific repetitive inspections or 
component replacements for equipment, systems, and installations. 
Accomplishment of these CMR items ensures that the likelihood of 
certain failures that could occur during operation of the airplane does 
not exceed the limitations specified in Federal Aviation Regulations 
(FAR) 25.1309, which is applicable to the design and approval of 
transport category airplanes.
    These CMR items are identified as a result of safety analyses of 
airplane electrical, electronic, pressurization, and propulsion 
systems. These analyses must be completed and approved by the FAA prior 
to its issuance of an airplane Type Certificate (TC). Following 
issuance of the TC, other necessary inspections, component 
replacements, or overhaul intervals for airplane systems that are based 
on in-service experience with the airplane, but that do not result in 
re-evaluation of the basic safety analysis on which approval of the 
system is based, are not included as additional CMR items; rather, 
these are addressed through changes to the airplane maintenance program 
or as the subjects of AD's.
    In conclusion, while the effect of a CMR item is the same as that 
of an AD requirement, its derivation is different. A CMR item is based 
on a statistical analysis required by FAR 25.1309; an AD requirement is 
based on follow-up work that is necessary to address an unsafe 
condition that is likely to exist or develop on other airplanes of the 
same type design.
    This AD addresses an unsafe condition identified as deployment of a 
thrust reverser during flight, and requires the installation of an 
additional thrust reverser system locking feature to correct that 
unsafe condition. The periodic functional tests contained in paragraph 
(e) of this AD are not the result of a re-evaluation of the safety 
analyses for Model 757 series airplanes with respect to FAR 25.1309 
requirements. These tests have been established to ensure the 
effectiveness of the modification required to address the identified 
unsafe condition. The FAA considers issuance of this AD to be 
necessary, since AD's are the means by which accomplishment of 
procedures and adherence to specific compliance times are made 
mandatory.
    ATA states further that, if the FAA finds sufficient justification 
to include the functional test requirements in this AD, an alternative 
to accomplishing paragraph (e) should be provided in the final rule. 
That alternative would include the following:
    1. Within 3 months after accomplishing the sync lock installation, 
operators would be required to revise the FAA-approved maintenance 
inspection program to include a functional test of the sync lock. The 
initial test would be accomplished within 1,000 hours time-in-service 
after modification. This AD would no longer be applicable for operators 
that have acceptably revised the maintenance program.
    2. Operators complying with this suggested alternative could use an 
alternative recordkeeping method in place of that otherwise required by 
FAR 91.417 or 121.380.
    3. For operators complying with this suggested alternative, the FAA 
would be defined as the cognizant Principal Maintenance Inspector 
(PMI).
    ATA reasons that its suggested alternative to accomplishing 
paragraph (e) of this AD is justified because no data exist to show 
that repetitive tests of a modified thrust reverser cannot be handled 
adequately through an operator's maintenance program.
    The FAA does not concur. As discussed previously, the FAA has 
determined that repetitive functional tests are necessary to ensure 
that the sync lock modification is effective in preventing the 
identified unsafe condition. This determination is based on the fact 
that the sync lock is a new design whose reliability has not been 
adequately proven through service experience. The ATA's proposal would 
enable each operator to determine whether and how often these tests 
should be conducted. In light of the severity of the identified unsafe 
condition, the FAA has determined that allowing this degree of operator 
discretion is inappropriate at this time. However, as the FAA obtains 
further information with regard to in-service experience, it may 
consider revising the requirements of paragraph (e) of this AD based on 
that new data.
    One commenter, Boeing, opposes the requirement contained in 
paragraph (e) of the proposal for periodic functional tests of the sync 
lock following accomplishment of the sync lock installation, and 
proposes that the paragraph be removed until the FAA reviews the ``more 
comprehensive'' scheduled maintenance recommendations developed by the 
Model 757/767 Thrust Reverser Working Group (TRWG). Boeing indicates 
that these more comprehensive tests will be recommended for maintenance 
of the thrust reverser system in the next revision to the Maintenance 
Review Board (MRB) report. Boeing also adds that the proposed interval 
at which the tests specified in paragraph (e) of this AD must be 
accomplished will be inconsistent with the next revision to the MRB 
report.
    Boeing states that any scheduled maintenance requirements for 
airplanes on which the sync lock installation has been accomplished 
should be presented at a Model 757 Industry Steering Committee meeting 
with the FAA, which is scheduled for December 1993. Boeing adds that, 
contingent upon FAA approval, recommendations developed by the TRWG 
will be included in Revision D to the MRB report, which will be 
published in the first quarter of 1994. Boeing believes that adoption 
of the maintenance recommendations contained in the forthcoming 
revision to the MRB report will ensure that an adequate level of 
safety, with regard to the sync lock installation, will be maintained 
by all operators of Model 757 series airplanes.
    The FAA does not concur with the commenter's request. The FAA finds 
that addressing the sync lock integrity test in a recommended action, 
such as the MRB report, will not ensure an acceptable level of safety 
with regard to the thrust reverser maintenance program. The FAA has 
determined that requiring the periodic functional tests of the sync 
lock integrity in this AD will provide an adequate level of safety.
    The FAA recognizes that differences exist currently where this AD 
requires that the sync lock integrity test be accomplished at more 
frequent intervals than those currently proposed by Boeing for 
inclusion in the MRB report. However, the FAA has determined that the 
test interval of 4,000 hours time-in-service, which will be recommended 
by Boeing for inclusion in the next revision to the MRB report, is too 
long in light of the sync lock function and the limited information 
available to substantiate in-service experience of the sync lock. 
Consequently, the FAA has based the requirement for accomplishment of 
the test at intervals of 1,000 hours time-in-service, as specified in 
paragraph (e) of this AD, on a philosophy that will ensure that all 
affected operators will accomplish a common sync lock integrity test at 
common intervals.
    The FAA anticipates that when the revised MRB report is issued in 
early 1994, that revision will contain a recommendation for 
accomplishment of the sync lock integrity test that is consistent with 
the requirements of paragraph (e) of this AD, thereby allowing the MRB 
to be consistent with AD-required actions.
    Several commenters request that the repetitive interval for 
functional tests of the sync lock installation be increased from the 
proposed 1,000 hours time-in-service to 3,000 hours time-in-service. 
One commenter states that, according to results of a check of the sync 
lock installation accomplished by Boeing, the proposed 1,000-hour 
functional test was intended to be accomplished only on Model 767 
series airplanes due to physical changes between the sync lock systems 
installed on Model 757 and 767 series airplanes. One commenter reasons 
that the proposed interval for functional tests of the sync lock device 
should be 3,000 hours time-in-service because AD 91-20-09 (which will 
be superseded by this proposed AD) specifies a 3,000-hour interval for 
inspections and tests of the thrust reverser system.
    The FAA does not concur with the commenters' request. The test 
interval specified in this AD is reduced from the interval specified in 
AD 91-20-09 because only limited information is available currently to 
substantiate the in-service reliability of the sync lock device. 
Consequently, the FAA has established an appropriate functional test 
interval to ensure all affected operators will accomplish a common sync 
lock integrity test at common intervals not to exceed 1,000 hours time-
in-service.
    ``Note 2'' of this final rule has been revised to state that 
paragraph ``(c)'' of this AD restates the requirement for repetitive 
inspections contained in paragraph (d) of AD 91-20-09, Amendment 39-
8043. An incorrect reference to paragraph ``(d)'' of this AD was made 
in ``Note 2'' of the supplemental NPRM.
    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 change previously 
described. The FAA has determined that this change will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.
    There are approximately 211 Model 757 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 192 
airplanes of U.S. registry will be affected by this AD, that it will 
take approximately 624 work hours per airplane to accomplish the 
required modification, and that the average labor rate is $55 per work 
hour. Required parts will be supplied by the manufacturer at no cost to 
operators. Based on these figures, the total cost impact of the AD on 
U.S. operators to accomplish the required modification is estimated to 
be $6,589,440, or $34,320 per airplane.
    The FAA recognizes that the required modification (sync lock 
installation) entails a large number of work hours to accomplish. 
However, the 5-year compliance time specified in paragraph (d) of this 
AD should allow ample time for the sync lock installation to be 
accomplished coincidentally with scheduled major airplane inspection 
and maintenance activities, thereby minimizing the costs associated 
with special airplane scheduling.
    In addition, the FAA estimates that 270 airplanes of U.S. registry 
will be required to accomplish the periodic functional tests required 
by this AD, that it will take approximately 1 work hour per airplane to 
accomplish each functional test, and that the average labor rate is $55 
per work hour. Based on these figures, the total cost impact of the AD 
on U.S. operators to accomplish each functional test is estimated to be 
$14,850, or $55 per airplane.
    Based on these figures, the total cost impact of the AD on U.S. 
operators is estimated to be $6,604,290. This total cost figure assumes 
that no operator has yet accomplished the requirements of this AD.
    The regulations adopted herein will not have substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government. Therefore, in 
accordance with Executive Order 12612, it is determined that this final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) will not have a 
significant economic impact, positive or negative, on a substantial 
number of small entities under the criteria of the Regulatory 
Flexibility Act. A final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it may be obtained 
from the Rules Docket at the location provided under the caption 
ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends 14 CFR part 
39 of the Federal Aviation Regulations 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 removing amendment 39-8043 (56 FR 
46725, September 16, 1991), and by adding a new airworthiness directive 
(AD), amendment 39-8792, to read as follows:

94-01-10 Boeing: Amendment 39-8792. Docket 92-NM-173-AD. Supersedes 
AD 91-20-09, Amendment 39-8043.

    Applicability: Model 757 series airplanes equipped with Pratt 
and Whitney PW2000 series engines, certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.

    Note 1: Paragraphs (a) and (b) of this AD restate the 
requirements of AD 91-20-09, Amendment 39-8043, paragraphs (a) and 
(b). As allowed by the phrase, ``unless accomplished previously,'' 
if the requirements of AD 91-20-09 have been accomplished 
previously, paragraphs (a) and (b) of this AD do not require those 
actions to be repeated.
    Note 2: Paragraph (c) of this AD restates the requirement for 
repetitive inspections contained in paragraph (d) of AD 91-20-09, 
Amendment 39-8043. Paragraph (c) of this AD requires that the first 
inspection required by this AD must be performed within the 
specified repetitive inspection interval after the last inspection 
performed in accordance with paragraph (d) of AD 91-20-09.

    To prevent deployment of a thrust reverser in flight and 
subsequent reduced controllability of the airplane, accomplish the 
following:
    (a) Within 14 days after September 16, 1991 (the effective date 
of AD 91-20-09, Amendment 39-8043), accomplish either paragraph 
(a)(1) or (a)(2) of this AD.
    (1) Accomplish both paragraphs (a)(1)(i) and (a)(1)(ii) of this 
AD:
    (i) Inspect the thrust reverser Directional Control Valve (DCV) 
assemblies of both engines to determine the solenoid-driven pilot 
valve's part number, in accordance with Boeing Alert Service 
Bulletin 757-78A0027, dated September 9, 1991.
    (A) If any DCV has a suspect pilot valve as specified in the 
service bulletin, prior to further flight, replace the DCV with a 
DCV that has a part number of a non-suspect solenoid-driven pilot 
valve, in accordance with the service bulletin.
    (B) If a DCV has a non-suspect solenoid-driven pilot valve as 
specified in the service bulletin, that pilot valve does not need to 
be replaced.
    (ii) Perform all tests and inspections of the engine thrust 
reverser control and indication system on both engines in accordance 
with Boeing Service Bulletin 757-78-0025, dated September 9, 1991. 
Prior to further flight, correct any discrepancy found in accordance 
with the service bulletin.
    (2) Accomplish paragraph (a)(1) of this AD on one engine's 
thrust reverser and deactivate the other engine's thrust reverser, 
in accordance with section 78-31-1 of Boeing Document D630N002, 
``Boeing 757 Dispatch Deviation Guide,'' Revision 8, dated January 
15, 1991.
    (b) Within 24 days after September 16, 1991 (the effective date 
of AD 91-20-09, Amendment 39-8043), the requirements of paragraph 
(a)(1) of this AD must be accomplished on both engines' thrust 
reverser systems.
    (c) Repeat the tests and inspections specified in paragraph 
(a)(1)(ii) at intervals not to exceed 3,000 flight hours, and prior 
to further flight following any maintenance that disturbs the thrust 
reverser control system. Prior to further flight, correct any 
discrepancy found in accordance with Boeing Service Bulletin 757-78-
0025, dated September 9, 1991.
    (d) Within 5 years after the effective date of this AD, install 
an additional thrust reverser system locking feature (sync lock 
installation), in accordance with Boeing Service Bulletin 757-78-
0028, Revision 1, dated October 29, 1992, or Revision 2, dated 
January 14, 1993.
    (e) Within 1,000 hours time-in-service after installing the sync 
lock required by paragraph (d) of this AD (either in production or 
by retrofit), or within 1,000 hours time-in-service after the 
effective date of this AD, whichever occurs later; and thereafter at 
intervals not to exceed 1,000 hours time-in-service: Perform 
functional tests of the sync lock in accordance with the ``Thrust 
Reverser Sync Lock Integrity Test'' procedures specified below. If 
any discrepancy is found during any test, prior to further flight, 
correct it in accordance with procedures described in the Boeing 757 
Maintenance Manual.

``Thrust Reverser Sync Lock Integrity Test

1. General
    A. Use this procedure to test the integrity of the thrust 
reverser sync locks.
2. Thrust Reverser Sync Lock Test
    A. Prepare for the Thrust Reverser Sync Lock Test.
    (1) Open the AUTO SPEEDBRAKE circuit breaker on the overhead 
circuit breaker panel, P11.
    (2) Do the steps that follow to supply power to the thrust 
reverser system:
    (a) Make sure the thrust levers are in the idle position.

    Caution: Do not extend the thrust reverser while the core cowl 
panels are open. Damage to the thrust reverser and core cowl panels 
can occur.

    (b) Make sure the thrust reverser halves are closed.
    (c) Make sure the core cowl panels are closed.
    (d) Put the EEC maint power switch or the EEC power L and EEC 
power R switches to the Altn position.
    (e) For the left engine:
    (1) Put the EEC MAINT CHANNEL SEL L switch to the AUTO position.
    (2) Put the L ENG fire switch to the NORM position.
    (f) For the right engine:
    (1) Put the EEC MAINT CHANNEL SEL R switch to the AUTO position.
    (2) Put the R ENG fire switch to the NORM position.
    (g) Make sure the EICAS circuit breakers (6 locations) are 
closed.

    Warning: The thrust reverser will automatically retract if the 
electrical power to the EEC/thrust reverser control system is turned 
off or if the EEC maint power switch is moved to the norm position. 
The accidental operation of the thrust reverser can cause injury to 
persons or damage to equipment can occur.
    (h) Make sure these circuit breakers on the main power 
distribution panel, P6, are closed:
    (1) Fuel cond cont L
    (2) Fuel cond cont R
    (3) T/L interlock L
    (4) T/L interlock R
    (5) Left T/R sync lock
    (6) Right T/R sync lock
    (7) L eng electronic engine control altn pwr (if installed)
    (8) R eng electronic engine control altn pwr (if installed)
    (i) Make sure these circuit breakers on the overhead circuit 
breaker panel, P11, are closed:
    (1) Air/gnd sys 1
    (2) Air/gnd sys 2
    (3) Landing gear pos sys 1
    (4) Landing gear pos sys 2
    (j) For the left engine, make sure these circuit breakers on the 
P11 panel are closed:
    (1) Left engine pdiu
    (2) Left engine thrust reverser cont/scav press
    (3) Left engine electronic engine control altn pwr (if 
installed)
    (4) Left engine thrust reverser pri cont
    (5) Left engine thrust reverser sec cont
    (k) For the right engine, make sure these circuit breakers on 
the P11 panel are closed:
    (1) Right engine pdiu
    (2) Right engine thrust reverser cont/scav press
    (3) Right engine electronic engine control altn pwr (if 
installed)
    (4) Right engine thrust reverser pri cont
    (5) Right engine thrust reverser sec cont
    (l) Supply electrical power.
    (m) Remove the pressure from the left (right) hydraulic system.
    B. Do the Thrust Reverser Sync Lock Test.
    (1) Move and hold the manual unlock lever on the center actuator 
on both thrust reverser sleeves to the unlock position.
    (2) Make sure the thrust reverser sleeves did not move.
    (3) Move the left (right) reverser thrust lever up and rearward 
to the idle detent position.
    (4) Make sure both thrust reverser sleeves move aft 
(approximately 0.15 to 0.25 inch).
    (5) Release the manual unlock lever on the center actuators.

    Warning: Make sure all persons and equipment are clear of the 
area around the thrust reverser. When you apply hydraulic pressure 
the thrust reverser will extend and can cause injuries to persons or 
damage to equipment.
    (6) Pressurize the left (right) hydraulic system.
    (7) Make sure the thrust reverser extends.
    (8) Move the left (right) reverser thrust lever to the fully 
forward and down position to retract the thrust reverser.
    C. Put the Airplane Back to its Usual Condition.
    (1) Remove hydraulic pressure.
    (2) Close the left and right fan cowls.
    (3) Close the AUTO SPEEDBRAKE circuit breaker on the P11 panel.
    (4) Remove electrical power if it is not necessary.
    D. Repeat the Thrust Reverser Sync Lock Test on the other 
engine.''

    (f) Installation of the sync lock, as required by paragraph (d) 
of this AD, constitutes terminating action for the requirements of 
paragraphs (a) through (c) of this AD.
    (g) 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, Seattle Aircraft Certification 
Office (ACO), FAA, Transport Airplane Directorate. Operators shall 
submit their requests through an appropriate FAA Principal 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Seattle ACO.

    Note 3: Approvals of alternative methods of compliance issued 
for AD 91-20-09 constitute valid approvals for compliance with the 
requirements of paragraphs (a) through (c) of this AD.

    Note 4: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (h) Special flight permits may be issued in accordance with FAR 
21.197 and 21.199 to operate the airplane to a location where the 
requirements of this AD can be accomplished.
    (i) The actions shall be done in accordance with Boeing Alert 
Service Bulletin 757-78A0027, dated September 9, 1991; Boeing 
Service Bulletin 757-78-0025, dated September 9, 1991; Boeing 
Document D630N002, ``Boeing 757 Dispatch Deviation Guide,'' Revision 
8, dated January 15, 1991; Boeing Service Bulletin 757-78-0028, 
Revision 1, dated October 29, 1992; and Boeing Service Bulletin 757-
78-0028, Revision 2, dated January 14, 1993. The incorporation by 
reference of Boeing Alert Service Bulletin 757-78A0027, dated 
September 9, 1991; Boeing Service Bulletin 757-78-0025, dated 
September 9, 1991; Boeing Document D630N002, ``Boeing 757 Dispatch 
Deviation Guide,'' Revision 8, dated January 15, 1991; was approved 
previously by the Director of the Federal Register in accordance 
with 5 U.S.C. 552(a) and 1 CFR part 51 as of September 16, 1991 (56 
FR 46725, September 16, 1991). The incorporation by reference of the 
remainder of the service documents listed above is approved by the 
Director of Federal Register in accordance with 5 U.S.C. 552(a) and 
1 CFR part 51. Copies may be obtained from Boeing Commercial 
Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. 
Copies may be inspected at the FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington; or at the Office of the 
Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.
    (j) This amendment becomes effective on March 3, 1994.

    Issued in Renton, Washington, on January 3, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-346 Filed 1-31-94; 8:45 am]
BILLING CODE 4910-13-P