[Federal Register Volume 64, Number 119 (Tuesday, June 22, 1999)]
[Proposed Rules]
[Pages 33229-33232]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-15774]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-252-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747-400 Series Airplanes

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 all Boeing Model 747-400 
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 August 6, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-252-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-252-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-252-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On July 13, 1994, the FAA issued AD 94-15-05, amendment 39-8976 (59 
FR 37655, July 25, 1994), applicable to all Boeing Model 747-400 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.
    In addition, this proposed AD changes the acceptable revision 
levels for Boeing Service Bulletin 747-78A2113, from the original 
issue, dated November 11, 1993, and Revision 1, dated March 10, 1994, 
referenced in AD 94-15-05 as the appropriate source of service 
information for accomplishment of the actions, to Revision 2, dated 
June 8, 1993 and Revision 3, dated September 11, 1997. Revisions 2 and 
3 of the service bulletin incorporate substantial technical changes. 
These revisions reduce the permitted resistance from 5.0 ohm to 4.0 ohm 
in the directional control valve hot short protection check, which 
ensures that the related circuit breaker will open if a hot short 
occurs. These revisions also add a step to

[[Page 33230]]

replace the bullnose seal in the next 650 flight hours if damage of 
more than 1 inch, but less than 10 inches is found during the bullnose 
seal inspection.

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 repetitive functional test of the CDU cone brake on each thrust 
reverser, and correction of any discrepancy found. The procedures for 
the functional test of the cone brake are essentially the same as those 
described in Boeing Service Bulletin 747-78-2113, dated November 11, 
1993, and Boeing Alert Service Bulletin 747-78A2113, Revision 1, dated 
March 10, 1994, for Model 747-400 series airplanes powered by General 
Electric CF6-80C2 series engines (which were referenced as appropriate 
sources of service information in AD 94-15-05). 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 Service Bulletin 747-78-2113 (1,000 flight hours).
    In addition, the FAA has reviewed and approved Boeing Service 
Bulletins 747-78-2113, Revision 2, dated June 8, 1995, and Revision 3, 
dated September 11, 1997. The procedures for the functional test of the 
cone brake are essentially the same as those described in Boeing 
Service Bulletin 747-78-2113, dated November 11, 1993, and Boeing Alert 
Service Bulletin 747-78A2113, Revision 1, dated March 10, 1994, 
referenced previously, for Model 747-400 series airplanes powered by 
General Electric CF6-80C2 series engines.
    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 94-15-05 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.

Differences 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 747-400 
series airplanes that are equipped with thrust reversers modified in 
accordance with Boeing Service Bulletin 747-78-2151 (or production 
equivalent). Boeing Model 747-400 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 proposed AD, however, would require that the cone brake 
functional test be performed on Model 747-400 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 747-78-2151. The FAA has determined that an inspection 
interval of 1,000 hours time-in-service (which was required by AD 94-
15-05) provides a sufficient level of safety for the modified thrust 
reversers, and that an inspection interval of 650 hours time-in-service 
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 146 Model 747-400 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 55 
airplanes of U.S. registry would be affected by this proposed AD.
    The new 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 
for thrust reversers that have not been modified). The current costs 
associated with AD 94-15-05 are reiterated in their entirety (as 
follows) for the convenience of affected operators.
    For airplanes powered by Pratt & Whitney PW4000 series engines (39 
U.S.-registered airplanes), the actions that are currently required by 
AD 94-15-05, and retained in this AD, take approximately 48 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 of Model 747-400 series airplanes powered by 
Pratt & Whitney PW4000 series engines is estimated to be $112,320, or 
$2,880 per airplane.
    For airplanes powered by General Electric CF6-80C2 series engines 
(16 U.S.-registered airplanes), the actions that are currently required 
by AD 94-15-05, and retained in this AD, take approximately 60 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 of Model 747-400 series airplanes 
powered by General Electric CF6-80C2 series engines is estimated to be 
$57,600, or $3,600 per airplane.
    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.
    Currently, there are no Model 747-400 series airplanes powered by 
Rolls-Royce RB211-524G/H series engines on the U.S. Register at this 
time. However, should one of these airplanes be imported and placed on 
the U.S. Register in the future, it will require approximately 30 hours 
to accomplish the required actions, at an average labor rate of $60 per 
work hour. Based on these figures, the cost impact of this AD is 
estimated to be $1,800 per airplane.

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''

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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 39-8976 (59 FR 
37655, July 25, 1994), and by adding a new airworthiness directive 
(AD), to read as follows:

Boeing: Docket 98-NM-252-AD. Supersedes AD 94-15-05, Amendment 39-
8976.

    Applicability: All Model 747-400 series airplanes, 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 (h)(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 94-15-05, Amendment 39-8976

Inspections and Tests

    (a) For Model 747-400 series airplanes powered by Pratt & 
Whitney PW4000 series engines: Accomplish paragraphs (a)(1) and 
(a)(2) of this AD.
    (1) Within 90 days after August 24, 1994 (the effective date of 
AD 94-15-05, amendment 39-8976), perform an inspection to detect 
damage to the bullnose seal on the translating sleeve of the thrust 
reverser, and perform a test of the lock mechanism of the center 
locking actuator, in accordance with paragraphs III.C. and III.E. of 
the Accomplishment Instructions of Boeing Service Bulletin 747-78-
2112, dated November 11, 1993; or paragraphs III.E. and III.H. of 
the Accomplishment Instructions of Boeing Alert Service Bulletin 
747-78A2112, Revision 1, dated March 7, 1994. Repeat this inspection 
and test thereafter at intervals not to exceed 1,000 hours time-in-
service.
    (2) Within 9 months after August 24, 1994, perform inspections 
and functional tests of the thrust reverser control and indication 
systems in accordance with paragraphs III.A., III.B., III.D., and 
III.F. through III.M. of the Accomplishment Instructions of Boeing 
Service Bulletin 747-78-2112, dated November 11, 1993; or paragraphs 
III.C., III.D., III.F., III.G., and III.I. through III.P. of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 747-
78A2112, Revision 1, dated March 7, 1994. Repeat these inspections 
and functional tests thereafter at intervals not to exceed 18 
months.

Inspections and Tests

    (b) For Model 747-400 series airplanes powered by General 
Electric CF6-80C2 series engines: Accomplish paragraphs (b)(1) and 
(b)(2) of this AD.
    (1) Within 90 days after August 24, 1994, perform an inspection 
to detect damage to the bullnose seal on the translating sleeve of 
the thrust reverser, and a continuity test of the position switch 
module of the center drive unit (CDU) and a cone brake test of the 
CDU, in accordance with paragraphs III.B. and III.C. of the 
Accomplishment Instructions of Boeing Service Bulletin 747-78-2113, 
dated November 11, 1993; or paragraphs III.E. through III.G. of 
Boeing Alert Service Bulletin 747-78A2113, Revision 1, dated March 
10, 1994; or Boeing Service Bulletin 747-78-2113, Revision 2, dated 
June 8, 1995, or Revision 3, dated September 11, 1997. Repeat the 
inspection and tests thereafter at intervals not to exceed 1,000 
hours time-in-service.
    (2) Within 9 months after August 24, 1994, perform inspections 
and functional tests of the thrust reverser control and indication 
systems in accordance with paragraphs III.A., III.D., III.F., 
III.G., III.H., and III.J. through III.M. of the Accomplishment 
Instructions of Boeing Service Bulletin 747-78-2113, dated November 
11, 1993; or paragraphs III.D. and III.H. through III.N. of Boeing 
Alert Service Bulletin 747-78A2113, Revision 1, dated March 10, 
1994; or Boeing Service Bulletin 747-78-2113, Revision 2, dated June 
8, 1995, or Revision 3, dated September 11, 1997. Repeat these 
inspections and functional tests thereafter at intervals not to 
exceed 18 months.

Inspections and Tests

    (c) For Model 747-400 series airplanes powered by Rolls-Royce 
RB211-524G/H series engines: Within 9 months after August 24, 1994, 
and thereafter at intervals not to exceed 18 months, perform 
inspections and functional tests of the thrust reverser control and 
indication systems in accordance with paragraphs III.D. through 
III.K. of the Accomplishment Instructions of Boeing Service Bulletin 
747-78-2115, dated October 28, 1993; or paragraphs III.D. through 
III.L. of the Accomplishment Instructions of Boeing Alert Service 
Bulletin 747-78A2115, Revision 1, dated March 4, 1994.

Corrective Action

    (d) If any of the inspections and/or functional tests required 
by this AD cannot be successfully performed, or if any discrepancy 
is found during those inspections and/or functional tests, 
accomplish either paragraph (d)(1) or (d)(2) of this AD.
    (1) Prior to further flight, correct the discrepancy found, in 
accordance with Boeing Service Bulletin 747-78-2112, dated November 
11, 1993, or Boeing Alert Service Bulletin 747-78A2112, Revision 1, 
dated March 7, 1994 (for Model 747-400 series airplanes powered by 
Pratt & Whitney PW4000 series engines); Boeing Service Bulletin 747-
78-2113, dated November 11, 1993, or Boeing Alert Service Bulletin 
747-78A2113, Revision 1, dated March 10, 1994, or Boeing Service 
Bulletin 747-78-2113, Revision 2, dated June 8, 1995, or Revision 3, 
dated September 11, 1997 (for Model 747-400 series airplanes powered 
by General Electric CF6-80C2 series engines); or Boeing Service 
Bulletin 747-78-2115, dated October 28, 1993, or Boeing Alert 
Service Bulletin 747-78A2115, Revision 1, dated March 4, 1994 (for 
Model 747-400 series airplanes powered by Rolls-Royce RB211-524G/H 
series engines); as applicable. 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

Functional Tests

    (e) For Model 747-400 series airplanes powered by General 
Electric CF6-80C2 series engines: 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 
the applicable section of paragraph III.A. of the Accomplishment 
Instructions of Boeing Service Bulletin 747-78-2113, Revision 2, 
dated June 8, 1995, or Revision 3, dated September 11, 1997.

[[Page 33232]]

    (1) For Model 747-400 series airplanes having line numbers 679 
through 1060 inclusive, equipped with thrust reversers that have not 
been modified in accordance with Boeing Service Bulletin 747-78-
2151: Repeat the functional test of the CDU cone brake thereafter at 
intervals not to exceed 650 hours time-in-service.
    (2) For Model 747-400 series airplanes having line numbers 1061 
and higher, equipped with thrust reversers that have been modified 
in accordance with Boeing Service Bulletin 747-78-2151: Repeat the 
functional test of the CDU cone brake thereafter at intervals not to 
exceed 1,000 hours time-in-service.

Terminating Action

    (f) Accomplishment of the functional test of the CDU cone brake, 
as specified in paragraphs (e)(1) and (e)(2) of this AD, as 
applicable, constitutes terminating action for the repetitive tests 
of the CDU cone brake required by paragraph (b)(1) of this AD.

Corrective Action

    (g) 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 (g)(1) or (g)(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 Boeing Service Bulletin 747-78-2113, 
Revision 2, dated June 8, 1995, or Revision 3, dated September 11, 
1997. 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.

Alternative Methods of Compliance

    (h)(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.
    (h)(2) Alternative methods of compliance for Model 747-400 
series airplanes powered by General Electric CF6-80C2 series 
engines, approved previously in accordance with AD 94-15-05, 
amendment 39-8976, are not considered to be approved as alternative 
methods of compliance with this AD.

    Note 2: 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

    (i) 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 June 15, 1999.
Dorenda D. Baker,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-15774 Filed 6-21-99; 8:45 am]
BILLING CODE 4910-13-P