[Federal Register Volume 64, Number 13 (Thursday, January 21, 1999)]
[Proposed Rules]
[Pages 3226-3228]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-1307]


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 Proposed Rules
                                                 Federal Register
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 This section of the FEDERAL REGISTER contains notices to the public of 
 the proposed issuance of rules and regulations. The purpose of these 
 notices is to give interested persons an opportunity to participate in 
 the rule making prior to the adoption of the final rules.
 
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  Federal Register / Vol. 64, No. 13 / Thursday, January 21, 1999 / 
Proposed Rules  

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-247-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747-200 and -300 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 747-
200 and -300 series airplanes, that currently requires various 
inspections and functional tests to detect discrepancies of the thrust 
reverser control and indication system, and correction of any 
discrepancy found. This action would reduce the repetitive interval for 
one certain functional test. This proposal is prompted by reports 
indicating that several center drive units (CDU) 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 March 8, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-247-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-247-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-247-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On March 3, 1995, the FAA issued AD 95-06-01, amendment 39-9171 (60 
FR 13623, March 14, 1995), applicable to certain Boeing Model 747-200 
and -300 series airplanes, to require various inspections and 
functional tests of the thrust reverser control and indication system, 
and correction of any discrepancy found. That action was prompted by an 
investigation to determine the controllability of Model 747 series 
airplanes following an in-flight thrust reverser deployment, which 
revealed that, in the event of thrust reverser deployment during high-
speed climb or during cruise, these airplanes could experience control 
problems. The requirements of that 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.

Actions Since Issuance of Previous Rule

    Since the issuance of that AD, the FAA has received reports 
indicating that several thrust reverser center drive units (CDU) 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.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 747-
78A2166, Revision 1, dated October 9, 1997, which describes procedures 
for a functional test of the CDU cone brake on each thrust reverser. 
The procedures for the functional test of the cone brake are 
substantially similar to those described

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in Boeing Alert Service Bulletin 747-78A2130, dated May 26, 1994 (which 
was referenced as the appropriate source of service information in AD 
95-06-01). However, Boeing Service Bulletin 747-78A2166, Revision 1, 
specifies a shorter repetitive interval for the functional test (650 
flight hours) than was specified in Boeing Alert Service Bulletin 747-
78A2130 (1,300 flight hours).
    The FAA previously reviewed and approved Boeing Alert Service 
Bulletin 747-78A2130, dated May 26, 1994, which describes procedures 
for various inspections and functional tests of the thrust reverser 
control and indication system (including a functional test of the CDU 
cone brake), and correction of any discrepancy found.
    Accomplishment of the actions specified in the service bulletins is 
intended to adequately address the identified unsafe condition.

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 95-06-01 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 
interval for the functional test of the CDU cone brake. The actions 
would be required to be accomplished in accordance with the service 
bulletins described previously, except as discussed below.

Difference Between Latest Service Bulletin and This Proposed AD

    Operators should note that Boeing Service Bulletin 747-78A2166, 
Revision 1, specifies that the functional test of the CDU cone brake 
described in that service bulletin is not necessary for Model 747-200 
and -300 series airplanes that are equipped with thrust reversers 
modified in accordance with Boeing Service Bulletin 747-78-2144 (or 
production equivalent). Boeing Model 747-200 and -300 series airplanes 
having line numbers 1061 and higher are equipped with such modified 
thrust reversers; therefore, the effectivity listing of Boeing Service 
Bulletin 747-78A2166, Revision 1, includes only Model 747 series 
airplanes equipped with General Electric Model CF6-80C2 engines having 
line numbers 679 through 1060 inclusive.
    This AD, however, would require that the cone brake functional test 
be performed on Model 747-200 and -300 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 747-78-2144. The FAA has determined that an inspection 
interval of 1,000 hours time-in-service (which was required by AD 95-
06-01) does not provide a sufficient level of safety for either the 
modified or 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 9 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 2 airplanes of U.S. registry 
would be affected by this proposed AD.
    The actions proposed by this AD would not add any additional 
economic burden on affected operators, other than the costs that are 
associated with repeating the functional test of the cone brake at 
reduced intervals (at intervals not to exceed 650 hours time-in-service 
rather than at intervals not to exceed 1,000 hours time-in-service). 
The current costs associated with AD 95-06-01 are reiterated in their 
entirety (as follows) for the convenience of affected operators.
    The actions that are currently required by AD 95-06-01, and 
retained in this AD, take approximately 33 work hours per airplane to 
accomplish, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of the currently required actions on 
U.S. operators is estimated to be $3,960, or $1,980 per airplane, per 
inspection/test cycle.
    The cost impact figure discussed above is 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.

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 39-9171 (60 FR 
13623, March 14, 1995), and by adding a new airworthiness directive 
(AD), to read as follows:

Boeing: Docket 98-NM-247-AD. Supersedes AD 95-06-01, Amendment 39-
9171.

    Applicability: Model 747-200 and -300 series airplanes equipped 
with General Electric Model CF6-80C2 series engines with Power 
Management Control engine controls, 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 (f) of 
this AD. The request should include an assessment of the

[[Page 3228]]

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 95-06-01

    (a) Within 90 days after April 13, 1995 (the effective date AD 
95-06-01, amendment 39-9171), perform tests of the position switch 
module and the cone brake of the center drive unit (CDU) on each 
thrust reverser, and perform an inspection to detect damage to the 
bullnose seal on the translating sleeve on each thrust reverser, in 
accordance with paragraphs III.A. through III.C. of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 747-
78A2130, dated May 26, 1994. Repeat the tests and inspection 
thereafter at intervals not to exceed 1,000 hours time-in-service 
until the functional test required by paragraph (d) of this AD is 
accomplished.
    (b) Within 9 months after April 13, 1995, perform inspections 
and functional tests of the thrust reverser control and indication 
system in accordance with paragraphs III.D. through III.F., III.H., 
and III.I. of the Accomplishment Instructions of Boeing Alert 
Service Bulletin 747-78A2130, dated May 26, 1994. Repeat these 
inspections and functional tests thereafter at intervals not to 
exceed 18 months.
    (c) If any of the inspections and/or functional tests required 
by paragraphs (a) and (b) of this AD cannot be successfully 
performed, or if any discrepancy is found during those inspections 
and/or functional tests, accomplish either paragraph (c)(1) or 
(c)(2) of this AD.
    (1) Prior to further flight, correct the discrepancy found, in 
accordance with Boeing Alert Service Bulletin 747-78A2130, dated May 
26, 1994. Or
    (2) The airplane may be operated in accordance with the 
provisions and limitations specified in an operator's FAA-approved 
Minimum Equipment List (MEL), provided that no more than one thrust 
reverser on the airplane is inoperative.

New Requirements of This AD

    (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 
747-78A2166, Revision 1, dated October 9, 1997, or paragraph III.B. 
of the Accomplishment Instructions of Boeing Alert Service Bulletin 
747-78A2130, dated May 26, 1994. Repeat the functional test 
thereafter at intervals not to exceed 650 hours time-in-service. 
Accomplishment of such functional test constitutes terminating 
action for the repetitive test of the CDU cone brake required by 
paragraph (a) of this AD.
    (e) If any functional test required by paragraph (d) of this AD 
cannot be successfully performed, or if any discrepancy is found 
during any functional test required by paragraph (d) of this AD, 
accomplish either paragraph (e)(1) or (e)(2) of this AD.
    (1) Prior to further flight, correct the discrepancy found, in 
accordance with Boeing Service Bulletin 747-78A2166, Revision 1, 
dated October 9, 1997, or paragraph III.B. of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 747-78A2130, dated May 
26, 1994. Or
    (2) The airplane may be operated in accordance with the 
provisions and limitations specified in the operator's FAA-approved 
MEL, provided that no more than one thrust reverser on the airplane 
is inoperative.
    (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, 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 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (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 airplane to a location where 
the requirements of this AD can be accomplished.

    Issued in Renton, Washington, on January 14, 1999.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-1307 Filed 1-20-99; 8:45 am]
BILLING CODE 4910-13-P