[Federal Register Volume 64, Number 113 (Monday, June 14, 1999)]
[Proposed Rules]
[Pages 31764-31769]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-14818]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-231-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 767 Series Airplanes 
Equipped With General Electric CF6-80C2 Series Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing 
airworthiness directive (AD), applicable to certain Boeing Model 767 
series airplanes, that currently requires tests, inspections, and 
adjustments of the thrust reverser system. That AD also requires 
installation of a terminating modification, and repetitive follow-on 
actions. This action would reduce the repetitive intervals for the 
follow-on actions. This proposal is prompted by reports indicating that 
several center drive units (CDU's) were returned to the manufacturer of 
the CDU's because of low holding torque of the CDU cone brake. The 
actions specified by the proposed AD are intended to ensure the 
integrity of the fail safe features of the thrust reverser system by 
preventing possible failure modes in the thrust reverser control system 
that can result in inadvertent deployment of a thrust reverser during 
flight.

DATES: Comments must be received by July 29, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-231-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

FOR FURTHER INFORMATION CONTACT: Holly Thorson, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-1357; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 98-NM-231-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 98-NM-231-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On June 22, 1995, the FAA issued AD 95-13-12, amendment 39-9292 (60 
FR 36976, July 19, 1995), as revised by AD 95-13-12 R1, amendment 39-
9528 (61 FR 9092, March 7, 1996), applicable to certain Boeing Model 
767 series airplanes, to require tests, inspections, and adjustments of 
the thrust reverser system. That AD also requires installation of a 
terminating modification, and repetitive operational checks of the 
electro-mechanical brake and the cone brake of the center drive unit 
(CDU) following accomplishment of the modification. That action was 
prompted by the identification of a modification that ensures that the 
level of safety inherent in the original type

[[Page 31765]]

design of the thrust reverser system is further enhanced. The 
requirements of that AD are intended to prevent possible discrepancies 
in the thrust reverser control system, which could result in 
inadvertent deployment of a thrust reverser during flight. The revision 
of the AD clarifies the requirements of AD 95-13-12 by specifying a 
revised number of pound-inches of torque that operators should use when 
performing the torque check of the cone brake of the CDU.

Actions Since Issuance of Previous Rule

    Since the issuance of AD 95-13-12 R1, the FAA has received reports 
indicating that several thrust reverser CDU's were returned to the 
manufacturer of the CDU's because of low holding torque of the CDU cone 
brake. This possible failure condition was not included in any previous 
safety assessment of the thrust reverser by the manufacturer. The 
returned CDU's had accumulated between 3,400 and 3,600 total flight 
hours. The cause of the low holding torque is a combination of cone 
brake wear, overrunning clutch wear, and grease contamination of the 
cone brake. Such a low torque condition could result in failure of the 
cone brake of the CDU, which could disable one of the fail safe 
features of the thrust reverser system that prevent deployment of a 
thrust reverser during flight.
    As a result of this failure condition, the manufacturer has 
submitted a revised safety analysis of the thrust reverser system and 
has defined specific intervals for accomplishing functional tests of 
the CDU cone brake and operational checks of the electro-mechanical 
brake, which occur more frequently than those defined in AD 95-13-12 
R1. The recommended intervals have been published in the Boeing 767 
Maintenance Planning Document.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 767-
78A0081, Revision 1, dated October 9, 1997, which describes procedures 
for a repetitive functional test of the CDU cone brake on each thrust 
reverser, and correction of any discrepancy detected. The procedures 
for the functional test of the cone brake are essentially the same as 
those described in Boeing Service Bulletin 767-78-0047, Revision 3, 
dated July 28, 1994 (which was referenced as an appropriate source of 
service information in AD 95-13-12) for Model 767 series airplanes 
equipped with General Electric CF6-80C2 series engines. However, Boeing 
Service Bulletin 767-78A0081, Revision 1, specifies a shorter 
repetitive interval for the functional test (650 flight hours) than was 
specified in Boeing Service Bulletin 767-78-0047, Revision 3 (1,000 
flight hours).

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would supersede AD 95-13-12 R1 to continue to require 
various inspections and functional tests to detect discrepancies of the 
thrust reverser control and indication system, and correction of any 
discrepancy found. This proposed AD would reduce the repetitive 
intervals for the functional test of the CDU cone brake and the 
operational check of the electro-mechanical brake. The functional test 
of the CDU cone brake would be required to be accomplished in 
accordance with the service bulletin described previously, except as 
discussed below.

Differences Between Service Bulletin and This Proposed AD

    Operators should note that Boeing Service Bulletin 767-78A0081, 
Revision 1, specifies that the functional test of the CDU cone brake 
described in that service bulletin is not necessary for Model 767 
series airplanes that are equipped with thrust reversers modified in 
accordance with Boeing Service Bulletin 767-78-0063 (or production 
equivalent). Boeing Model 767 series airplanes having line numbers 475 
and higher are equipped with such modified thrust reversers; therefore, 
the effectivity listing of Boeing Service Bulletin 767-78A0081, 
Revision 1, includes only Model 767 series airplanes equipped with 
General Electric Model CF6-80C2 engines having line numbers prior to 
475.
    This proposed AD, however, would require that the cone brake 
functional test be performed on Model 767 series airplanes equipped 
with General Electric Model CF6-80C2 engines regardless of whether they 
are equipped with thrust reversers modified in accordance with Boeing 
Service Bulletin 767-78-0063. The FAA has determined that an inspection 
interval of 1,000 hours time-in-service (for both the CDU cone brake 
and the electro-mechanical brake) provides a sufficient level of safety 
for the modified thrust reversers, and that 650 hours time-in-service 
(for the CDU cone brake) provides a sufficient level of safety for the 
unmodified thrust reversers, given the low holding torque condition 
that has been identified for the CDU cone brake.

Interim Action

    This is considered to be interim action. The manufacturer has 
advised that it currently is developing a modification that will 
positively address the unsafe condition addressed by this AD. Once this 
modification is developed, approved, and available, the FAA may 
consider additional rulemaking.

Cost Impact

    There are approximately 143 Boeing Model 767 series airplanes 
equipped with General Electric CF6-80C2 series engines in the worldwide 
fleet. The FAA estimates that 45 airplanes of U.S. registry would be 
affected by this proposed AD.
    The tests, inspections, and adjustments that are currently required 
by AD 95-13-12, and retained in this proposed AD, take approximately 30 
work hours per airplane to accomplish, at an average labor rate of $60 
per work hour. Based on these figures, the cost impact on U.S. 
operators of the currently required tests, inspections, and adjustments 
that are retained in this proposed AD is estimated to be $81,000, or 
$1,800 per airplane, per inspection cycle.
    The terminating modification currently required by AD 95-13-12, and 
retained in this proposed AD, take approximately 786 work hours per 
airplane to accomplish, at an average labor rate of $60 per work hour. 
Required parts will be provided by the manufacturer at no cost to the 
operator. Based on these figures, the cost impact on U.S. operators of 
the terminating modification required by this proposed AD is estimated 
to be $2,122,200, or $47,160 per airplane.
    The repetitive operational checks required by AD 95-13-12, and 
retained in this proposed AD, take approximately 2 work hours per 
airplane to accomplish, at an average labor rate of $60 per work hour. 
Based on these figures, the cost impact on U.S. operators of the 
repetitive operational checks required by this proposed AD is estimated 
to be $5,400, or $120 per airplane, per operational check cycle.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the current or proposed 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this AD were not adopted.
    The FAA has been advised that the terminating modification has been 
accomplished in accordance with the

[[Page 31766]]

requirements of this AD on 45 U.S.-registered airplanes. Therefore, the 
future economic cost impact of this rule on U.S. operators is now only 
the cost associated with the repetitive operational checks required by 
this AD.
    The number of required work hours for each requirement of AD 95-13-
12 R1, as indicated above, is presented as if the accomplishment of the 
actions were to be conducted as ``stand alone'' actions. However, in 
actual practice, these actions for the most part will be accomplished 
coincidentally or in combination with normally scheduled airplane 
inspections and other maintenance program tasks. Therefore, the actual 
number of necessary additional work hours will be minimal in many 
instances. Additionally, any costs associated with special airplane 
scheduling will be minimal.

Regulatory Impact

    The regulations proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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 copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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 removing amendment 39-9528 (61 FR 
9092, March 7, 1996), and by adding a new airworthiness directive (AD), 
to read as follows:

Boeing: Docket 98-NM-231-AD. Supersedes AD 95-13-12 R1, Amendment 
39-9528.

    Applicability: Model 767 series airplanes equipped with General 
Electric CF6-80C2 series engines, certificated in any category.

    Note 1: This AD applies to each airplane 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 airplanes 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 (g)(1) 
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 ensure the integrity of the fail safe features of the thrust 
reverser system by preventing possible failure modes in the thrust 
reverser control system that can result in inadvertent deployment of 
a thrust reverser during flight, accomplish the following:

Restatement of Requirements of AD 95-13-12 R1, Amendment 39-9528:

    (a) Within 30 days after August 18, 1995 (the effective date of 
AD 95-13-12 R1, amendment 39-9528), perform tests, inspections, and 
adjustments of the thrust reverser system in accordance with Boeing 
Service Bulletin 767-78-0047, Revision 3, dated July 28, 1994.
    (1) Except as provided by paragraph (a)(2) of this AD, repeat 
all tests and inspections thereafter at intervals not to exceed 
3,000 flight hours until the modification required by paragraph (c) 
of this AD is accomplished.
    (2) Repeat the check of the grounding wire for the Directional 
Pilot Valve (DPV) of the thrust reverser in accordance with the 
service bulletin at intervals not to exceed 1,500 flight hours, and 
whenever maintenance action is taken that would disturb the DPV 
grounding circuit, until the modification required by paragraph (c) 
of this AD is accomplished.
    (b) If any of the tests and/or inspections required by paragraph 
(a) of this AD cannot be successfully performed, or if those tests 
and/or inspections result in findings that are unacceptable in 
accordance with Boeing Service Bulletin 767-78-0047, Revision 3, 
dated July 28, 1994; accomplish paragraphs (b)(1) and (b)(2) of this 
AD.
    (1) Prior to further flight, deactivate the associated thrust 
reverser in accordance with Section 78-31-1 of Boeing Document 
D630T002, ``Boeing 767 Dispatch Deviation Guide,'' Revision 9, dated 
May 1, 1991; or Revision 10, dated September 1, 1992. After August 
18, 1995, this action shall be accomplished only in accordance with 
Revision 10 of the Boeing document. No more than one reverser on any 
airplane may be deactivated under the provisions of this paragraph.
    (2) Within 10 days after deactivation of any thrust reverser in 
accordance with this paragraph, the thrust reverser must be repaired 
in accordance with Boeing Service Bulletin 767-78-0047, Revision 3, 
dated July 28, 1994. Additionally, the tests and/or inspections 
required by paragraph (a) of this AD must be successfully 
accomplished; once this is accomplished, the thrust reverser must 
then be reactivated.
    (c) Within 3 years after August 18, 1995, install a third 
locking system on the left-and right-hand engine thrust reversers in 
accordance with Boeing Service Bulletin 767-78-0063, Revision 2, 
dated April 28, 1994.

New Requirements of this AD

    Note 2: Boeing Service Bulletin 767-78-0063, references General 
Electric (GE) Service Bulletin 78-135 as an additional source of 
service information for accomplishment of the third locking system 
on the thrust reversers. However, the Boeing Service Bulletin does 
not specify the appropriate revision level, and the GE service 
bulletin has a new Lockheed Martin title for the same service 
bulletin: Lockheed Martin Service Bulletin 78-135, Revision 4, dated 
September 30, 1996. The appropriate revision level for the GE 
Service Bulletin is Revision 3, dated August 2, 1994. The GE and 
Lockheed Martin service bulletins are identical, and either may be 
used for accomplishment of the action described previously.

    Note 3: The actions specified in Lockheed Martin Service 
Bulletin 78-1007, Revision 1, dated March 18, 1997; and Lockheed 
Martin Service Bulletin 78-1020, Revision 2, dated March 20, 1997; 
may be accomplished simultaneously in conjunction with Boeing 
Service Bulletin 767-78-0063 for accomplishment of the installation 
of the thrust reverser bracket and the thrust reverser lock. 
(Accomplishment of these two service bulletins together achieves the 
same results as Lockheed Martin Service Bulletin 78-135, Revision 4, 
and is acceptable for compliance with Boeing Service Bulletin 767-
78-0063.)

    (d) Within 1,000 hours time-in-service after the most recent 
test of the CDU cone brake performed in accordance with paragraph 
(a) of this AD, or within 650 hours time-in-service after the 
effective date of this AD, whichever occurs first: Perform a 
functional test to detect discrepancies of the CDU cone brake on 
each thrust reverser, in accordance with Boeing Service Bulletin 
767-78A0081, Revision 1, dated October 9, 1997, or Appendix 1 
(including Figure 1), sections 1.A.(2), 2.A., 2.C., and 2.D of this 
AD.
    (1) For Model 767 series airplanes, line numbers up to and 
including 474, equipped with thrust reversers that have not been

[[Page 31767]]

modified in accordance with Boeing Service Bulletin 767-78-0063: 
Repeat the functional test of the CDU cone brake thereafter at 
intervals not to exceed 650 hours time-in-service.
    (2) For Model 767 series airplanes, line numbers 475 and 
subsequent; and Model 767 series airplanes equipped with thrust 
reversers that have been modified in accordance with Boeing Service 
Bulletin 767-78-0063: Repeat the functional test of the CDU cone 
brake thereafter at intervals not to exceed 1,000 hours time-in-
service.
    (e) Within 1,000 flight hours after accomplishing the 
modification required by paragraph (c) of this AD, or within 1,000 
flight hours after the effective date of this AD, whichever occurs 
later: Perform operational checks of the electro-mechanical brake in 
accordance with Appendix 1 (including Figure 1), sections 1.A.(1), 
2.A., 2.B., and 2.D of this AD. Repeat the operational checks 
thereafter at intervals not to exceed 1,000 flight hours.

Terminating Action

    (f) Accomplishment of the modification and periodic operational 
checks required by paragraphs (c), (d), and (e) of this AD 
constitutes terminating action for the tests, inspections, and 
adjustments required by paragraph (a) of this AD.

Alternative Methods of Compliance

    (g)(1) 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.
    (g)(2) Alternative methods of compliance, approved previously in 
accordance with AD 95-13-12, amendment 39-9292, are approved as 
alternative methods of compliance with 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.

Special Flight Permits

    (h) Special flight permits may be issued in accordance with 
Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 
21.197 and 21.199) to operate the airplane to a location where the 
requirements of this AD can be accomplished.

Appendix 1--Thrust Reverser Electro-Mechanical Brake and CDU Cone Brake 
Test

1. General

    A. This procedure contains steps to do two checks:
    (1) A check of the holding torque of the electro-mechanical 
brake.
    (2) A check of the holding torque of the CDU cone brake.

2. Electro-Mechanical Brake and CDU Cone Brake Torque Check (Fig. 
1)

    A. Prepare to do the checks:
    (1) Open the fan cowl panels.
    B. Do a check of the torque of the electro-mechanical brake:
    (1) Do a check of the running torque of the thrust reverser 
system:
    (a) Manually extend the thrust reverser six inches and measure 
the running torque.
    (1) Make sure the torque is less than 10 pound-inches.
    (2) Do a check of the electro-mechanical brake holding torque:
    (a) Make sure the thrust reverser translating cowl is extended 
at least one inch.
    (b) Make sure the CDU lock handle is released.
    (c) Pull down on the manual release handle on the electro-
mechanical brake until the handle fully engages the retaining clip.

    Note: This will lock the electro-mechanical brake.

    (d) With the manual drive lockout cover removed from the CDU, 
install a \1/4\-inch extension tool and dial-type torque wrench into 
the drive pad.

    Note: You will need a 24-inch extension to provide adequate 
clearance for the torque wrench.

    (e) Apply 90 pound-inches of torque to the system.
    (1) The electro-mechanical brake system is working correctly if 
the torque is reached before you turn the wrench 450 degrees (1-1/4 
turns).
    (2) If the flexshaft turns more than 450 degrees before you 
reach the specified torque, you must replace the long flexshaft 
between the CDU and the upper angle gearbox.
    (3) If you do not get 90 pound-inches of torque, you must 
replace the electro-mechanical brake.
    (f) Release the torque by turning the wrench in the opposite 
direction until you read zero pound-inches.
    (1) If the wrench does not return to within 30 degrees of 
initial starting point, you must replace the long flexshaft between 
the CDU and upper angle gearbox.
    (3) Fully retract the thrust reverser.
    C. Do a check of the CDU cone brake:
    (1) Pull up on the manual release handle to unlock the electro-
mechanical brake.
    (2) Pull the manual brake release lever on the CDU to release 
the cone brake.

    Note: This will release the pre-load tension that may occur 
during a stow cycle.

    (3) Return the manual brake release lever to the locked position 
to engage the cone brake.
    (4) Remove the two bolts that hold the lockout plate to the CDU 
and remove the lockout plate.
    (5) Install a \1/4\-inch drive and a dial type torque wrench 
into the CDU drive pad.
    CAUTION: DO NOT USE MORE THAN 100 POUND-INCHES OF TORQUE WHEN 
YOU DO THIS CHECK. EXCESSIVE TORQUE WILL DAMAGE THE CDU.
    (6) Turn the torque wrench to try to manually extend the 
translating cowl until you get at lease 15-pound inches.

    Note: The cone brake prevents movement in the extend direction 
only. If you try to measure the holding torque in the retract 
direction, you will get a false reading.

    (a) If the torque is less than 15-pound-inches, you must replace 
the CDU.
    D. Return the airplane to its usual condition:
    (1) Fully retract the thrust reverser (unless already 
accomplished).
    (2) Pull down on the manual release handle on the electro-
mechanical brake until the handle fully engages the retaining clip 
(unless already accomplished).

    Note: This will lock the electro-mechanical brake.

    (3) Close the fan cowl panels.

BILLING CODE 4910-13-P

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[GRAPHIC] [TIFF OMITTED] TP14JN99.053




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    Issued in Renton, Washington, on June 4, 1999.
Vi L. Lipski,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-14818 Filed 6-11-99; 8:45 am]
BILLING CODE 4910-13-C