[Federal Register Volume 64, Number 207 (Wednesday, October 27, 1999)]
[Proposed Rules]
[Pages 57802-57806]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-28084]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NM-64-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: This document proposes the adoption of a new airworthiness
directive (AD) that is applicable to certain Boeing Model 747 series
airplanes equipped with General Electric Model CF6-45 or -50 series
engines. This proposal would require repetitive inspections and tests
of the thrust reverser control and indication system, and corrective
actions, if necessary. This proposal would also require installation of
a thrust reverser actuation system (TRAS) lock, repetitive functional
tests of that installation, and repair, if necessary. Installation of
the TRAS lock would terminate the repetitive inspections and certain
tests. This proposal is prompted by the results of a safety review,
which revealed that in-flight deployment of a thrust reverser could
result in a significant reduction in airplane controllability. 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, which could result in inadvertent
deployment of a thrust reverser during flight, and consequent reduced
controllability of the airplane.
DATES: Comments must be received by December 13, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 99-NM-64-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: Larry Reising, Aerospace Engineer,
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate,
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (425) 227-2683; 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.
[[Page 57803]]
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 99-NM-64-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. 99-NM-64-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
On May 26, 1991, a Boeing Model 767-300ER series airplane was
involved in an accident as a result of an uncommanded in-flight
deployment of a thrust reverser. Following that accident, a study was
conducted to evaluate the potential effects of an uncommanded thrust
reverser deployment throughout the flight regime of other Boeing
airplane models, including the Boeing Model 747 series airplane
equipped with General Electric Model CF6-45 or -50 series engines. The
study included a re-evaluation of the thrust reverser control system
fault analysis and airplane controllability. The results of the
evaluation revealed that, if not prevented, possible combinations of
failures within the thrust reverser control system may result in an in-
flight deployment of a thrust reverser and that, in the event of thrust
reverser deployment during high-speed climb using high engine power, or
during cruise, these airplanes may not be controllable.
The FAA has prioritized the issuance of AD's for corrective actions
for the thrust reverser system on Boeing airplane models following the
1991 accident. Based on service experience, analyses, and flight
simulator studies, it was determined that an in-flight deployment of a
thrust reverser has more effect on controllability of twin-engine
airplane models than of Model 747 series airplanes, which have four
engines. For this reason, the highest priority was given to rulemaking
that required corrective actions for the twin-engine airplane models.
AD's that correct the same type of unsafe condition as that addressed
by this AD have been previously issued for specific airplanes within
the Boeing Model 737, 757, and 767 series.
Service experience has shown that in-flight thrust reverser
deployments have occurred on Model 747 airplanes in certain flight
conditions with no significant airplane controllability problems being
reported. However, the manufacturer has been unable to establish that
acceptable airplane controllability would be achieved throughout the
operating envelope of the airplane following such a deployment.
Additionally, safety analyses performed by the manufacturer and
reviewed by the FAA, have been unable to establish that the risks for
uncommanded thrust reverser deployment at critical flight conditions
are acceptably low.
Explanation of Relevant Service Information
The FAA has reviewed and approved the following service bulletins:
Boeing Alert Service Bulletin 747-78A2160, dated May 4,
1995, including Notice of Status Change 747-78A2160 NSC 1, dated June
8, 1995, describes procedures for repetitive inspections and tests to
verify proper operation of the thrust reverser stow/deploy switches,
the bullnose seals, the airmotor brake, the overpressure shutoff valve
electrical connectors, the flexible shafts, the directional pilot
valve, and the microswitch pack on each engine; and repair, if
necessary.
Boeing Service Bulletin 747-78-2150, Revision 1, dated
July 2, 1998, describes procedures for installation of a thrust
reverser actuation system (TRAS) lock on each thrust reverser half of
each engine. This service bulletin specifies that prior or concurrent
incorporation of Boeing Service Bulletin 747-78-2067, Boeing Service
Bulletin 747-78-2069, Boeing Service Bulletin 747-78-2133, Middle River
Aircraft Systems CF6-50 Service Bulletin 78-3011, and Middle River
Aircraft Systems CF6-50 Service Bulletin 78-3013, is necessary. Such
installation eliminates the need for the repetitive inspections and
tests described in Boeing Alert Service Bulletin 747-78A2160.
The FAA has also reviewed Chapter 78-34-00 of the Boeing 747
Maintenance Manual, dated April 25, 1998, which describes procedures
for repetitive functional tests of the TRAS lock.
Accomplishment of the modification specified in Boeing Service
Bulletin 747-78-2150, Revision 1, and the repetitive functional tests
specified in the maintenance manual are intended to adequately address
the identified unsafe condition.
The modification procedures described by Boeing Service Bulletin
747-78-2150, dated March 20, 1997, have been validated previously, and
the necessary changes have been incorporated into Revision 1 of the
service bulletin. The FAA has determined that the procedures described
by Boeing Service Bulletin 747-78-2150, Revision 1, and the numerous
referenced service bulletins, have been sufficiently validated to now
propose that this modification be required. Several airplanes have been
successfully modified in accordance with the service bulletin, and this
past experience should minimize the likelihood for subsequent service
bulletin revisions, requests for alternative methods of compliance, and
superseding AD's.
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 require repetitive inspections and tests of the
thrust reverser control and indication system, and corrective actions,
if necessary. The proposed AD would also require installation of a TRAS
lock, repetitive functional tests of that installation, and repair, if
necessary. Installation of the TRAS lock would terminate the repetitive
inspections and certain tests.
This proposed AD would also include a provision for deactivation of
one thrust reverser in accordance with Section 78-1 of Boeing Document
D6-33391, ``Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures
Guide,'' Revision 22, dated January 30, 1998. No more than one thrust
reverser on any airplane may be deactivated under the provisions of
this document.
Differences Between Proposed Rule and Service Bulletins
The effectivity of Boeing Alert Service Bulletin 747-78A2160
identifies all Model 747-100 and -200 series airplanes powered by
General Electric Model CF6-45 or -50 series engines, line numbers 232
through 886 inclusive; however, this proposed AD would apply to all
Model 747 series airplanes powered by General Electric Model CF6-45 or
-50 series engines. The FAA has been notified by the airplane
[[Page 57804]]
manufacturer that there are Model 747-300 and 747SR series airplanes,
and airplanes having line numbers lower than 232, that are powered by
Model CF6-45 or -50 series engines.
Operators should note that, although Boeing Alert Service Bulletin
747-78A2160 recommends accomplishing the inspections and tests within
1,500 flight hours or 4 months (after the release of the service
bulletin), the FAA has determined that the recommended interval would
not address the identified unsafe condition in a timely manner. In
developing an appropriate compliance time for this AD, the FAA
considered not only the manufacturer's recommendation, but the degree
of urgency associated with addressing the subject unsafe condition, the
average utilization of the affected fleet, and the time necessary to
perform the inspection. In light of all of these factors, the FAA finds
a 90-day compliance time for initiating the inspections and tests of
the thrust reverser stow/deploy switches, the bullnose seals, and the
airmotor brakes; and a 6-month compliance time for initiating the
inspections and tests of the overpressure shutoff valve electrical
connectors, the flexible shafts, the directional pilot valves, and the
microswitch packs; to be warranted, in that those times represent
appropriate intervals of time allowable for affected airplanes to
continue to operate without compromising safety.
Operators should also note that, although Boeing Service Bulletin
747-78-2150, Revision 1, does not specify a compliance time for
accomplishment of installation of the TRAS locks, this proposal would
require that action to be accomplished within 36 months after the
effective date of this AD. In developing an appropriate compliance time
for this proposed AD, the FAA considered the degree of urgency
associated with addressing the subject unsafe condition, the average
utilization of the affected fleet, and the time necessary to accomplish
the proposed actions (approximately 791 work hours).
In light of these factors, the FAA finds a compliance time of 36
months for accomplishing the proposed actions to be warranted, in that
it represents an appropriate interval of time allowable for affected
airplanes to continue to operate without compromising safety.
Although not described in either service bulletin, this proposed AD
would allow the option to dispatch an airplane with one thrust reverser
deactivated and operate the airplane for up to 10 days with one thrust
reverser deactivated. This option would be allowed in the event of
unsuccessful accomplishment of the repetitive inspections and tests
specified in paragraphs (a) and (b) of this AD or installation of a
spare thrust reverser assembly with a different configuration than that
installed on the other engines of the airplane.
Cost Impact
There are approximately 138 airplanes of the affected design in the
worldwide fleet. The FAA estimates that 27 airplanes of U.S. registry
would be affected by this proposed AD.
It would take approximately 12 work hours per airplane to
accomplish the proposed inspections and tests of the thrust reverser
stow/deploy switches, the bullnose seals, and the airmotor brakes, at
an average labor rate of $60 per work hour. Based on these figures, the
cost impact of the proposed repetitive inspections and tests on U.S.
operators is estimated to be $19,440, or $720 per airplane, per
inspection and test cycle.
It would take approximately 11 work hours per airplane to
accomplish the proposed inspections and tests of the overpressure
shutoff valve electrical connectors, the flexible shafts, the
directional pilot valves, and the microswitch packs, at an average
labor rate of $60 per work hour. Based on these figures, the cost
impact of the proposed repetitive inspections and tests on U.S.
operators is estimated to be $17,820, or $660 per airplane, per
inspection and test cycle.
It would take approximately 791 work hours per airplane to
accomplish the proposed installation of TRAS locks, at an average labor
rate of $60 per work hour. Required parts would be provided at no cost
by the airplane manufacturer. Based on these figures, the cost impact
of the proposed installation on U.S. operators is estimated to be
$1,281,420, or $47,460 per airplane.
This cost impact figure does not reflect the cost of the
modifications described in the service bulletins listed in paragraph
I.K.1.h. of Boeing Service Bulletin 747-78-2150, Revision 1, that are
proposed to be accomplished prior to, or concurrently with, the
installation of the TRAS lock. (The cost impact figure does reflect the
cost of the modifications described in the service bulletins listed in
paragraph I.K.1.j. of the service bulletin that are also proposed to be
accomplished prior to, or concurrently with, the installation of the
TRAS lock.) Since some operators may have accomplished certain
modifications on some or all of the airplanes in its fleet, while other
operators may not have accomplished any of the modifications on any of
the airplanes in its fleet, the FAA is unable to provide a reasonable
estimate of the cost of accomplishing the terminating actions described
in the service bulletins listed in paragraph I.K.1.h. of Boeing Service
Bulletin 747-78-2150. As indicated earlier in this preamble, the FAA
invites comments specifically on the overall economic aspects of this
proposed rule. Any data received via public comments to this proposed
AD will aid the FAA in developing an accurate accounting of the cost
impact of the rule.
It would take approximately 4 work hours per airplane to accomplish
the proposed functional test of the TRAS lock, at an average labor rate
of $60 per work hour. Based on these figures, the cost impact of the
proposed repetitive functional tests on U.S. operators is estimated to
be $6,480, or $240 per airplane, per test cycle.
The cost impact figures discussed above are based on assumptions
that no operator has yet accomplished any of the 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.
[[Page 57805]]
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 adding the following new
airworthiness directive:
Boeing: Docket 99-NM-64-AD.
Applicability: Model 747 series airplanes; certificated in any
category; equipped with General Electric Model CF6-45 or -50 series
engines.
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) 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, which could
result in inadvertent deployment of a thrust reverser during flight,
and consequent reduced controllability of the airplane, accomplish
the following:
Repetitive Inspections and Tests
Note 2: For the purposes of this AD, a detailed visual
inspection is defined as: ``An intensive visual examination of a
specific structural area, system, installation, or assembly to
detect damage, failure, or irregularity. Available lighting is
normally supplemented with a direct source of good lighting at
intensity deemed appropriate by the inspector. Inspection aids such
as mirror, magnifying lenses, etc., may be used. Surface cleaning
and elaborate access procedures may be required.''
(a) Within 90 days after the effective date of this AD, perform
the applicable detailed visual inspections and tests to verify
proper operation of the thrust reverser stow/deploy switches, the
bullnose seals, and the airmotor brake on each engine, in accordance
with Work Package I of the Accomplishment Instructions of Boeing
Alert Service Bulletin 747-78A2160, dated May 4, 1995, including
Notice of Status Change 747-78A2160 NSC 1, dated June 8, 1995.
Repeat the applicable inspections and tests thereafter at intervals
not to exceed 1,300 flight hours, until accomplishment of paragraph
(d) of this AD.
(b) Within 6 months after the effective date of this AD, perform
the applicable detailed visual inspections and tests to verify
proper operation of the overpressure shutoff valve electrical
connectors, the flexible shafts, the directional pilot valve, and
the microswitch pack on each engine, in accordance with Work Package
II of the Accomplishment Instructions of Boeing Alert Service
Bulletin 747-78A2160, dated May 4, 1995, including Notice of Status
Change 747-78A2160 NSC 1, dated June 8, 1995. Repeat the applicable
inspections and tests thereafter at intervals not to exceed 18
months, until accomplishment of paragraph (d) of this AD.
Corrective Actions
(c) If any of the inspections and tests required by paragraphs
(a) and (b) of this AD cannot be successfully performed, or if any
discrepancy is detected during the inspections and tests, accomplish
paragraphs (c)(1) or (c)(2) of this AD, as applicable.
(1) Prior to further flight, repair in accordance with Boeing
Alert Service Bulletin 747-78A2160, dated May 4, 1995. Additionally,
prior to further flight, any failed inspection or test required by
paragraph (a) or (b) of this AD must be repeated and successfully
accomplished.
(2) Accomplish both paragraphs (c)(2)(i) and (c)(2)(ii) of this
AD.
(i) Prior to further flight, deactivate the associated thrust
reverser in accordance with Section 78-1 of Boeing Document D6-
33391, ``Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures
Guide,'' Revision 22, dated January 30, 1998. No more than one
thrust reverser on any airplane may be deactivated under the
provisions of this paragraph.
Note 3: The airplane may be operated in accordance with the
provisions and limitations specified in the operator's FAA-approved
Master Minimum Equipment List, provided that no more than one thrust
reverser on the airplane is inoperative.
(ii) Within 10 days after deactivation of any thrust reverser in
accordance with paragraph (c)(2)(i) of this AD, the affected thrust
reverser must be repaired in accordance with Boeing Alert Service
Bulletin 747-78A2160, dated May 4, 1995. Additionally, prior to
further flight, any failed inspection or test required by paragraph
(a) or (b) of this AD must be repeated and successfully
accomplished; once such inspections and tests have been successfully
accomplished, the thrust reverser may then be reactivated.
Modification
(d) Within 36 months after the effective date of this AD,
install a thrust reverser actuation system (TRAS) lock on each
thrust reverser half of each engine, in accordance with Boeing
Service Bulletin 747-78-2150, Revision 1, dated July 2, 1998. All of
the modifications described in the service bulletins listed in
paragraphs I.K.1.h. and I.K.1.j. of Boeing Service Bulletin 747-78-
2150, Revision 1, must be accomplished, as applicable, in accordance
with those service bulletins, prior to, or concurrently with, the
accomplishment of the installation of the TRAS lock. Accomplishment
of these actions constitutes terminating action for the repetitive
inspections required by paragraphs (a) and (b) of this AD.
Note 4: Accomplishment of the installation specified in Boeing
Service Bulletin 747-78-2150, dated March 20, 1997, is acceptable
for compliance with the installation required by paragraph (d) of
this AD.
Functional Tests
(e) Within 3,000 flight hours after accomplishing the
modification required by paragraph (d) of this AD, or within 1,000
flight hours after the effective date of this AD, whichever occurs
later, perform a functional test of the TRAS lock on each reverser
half, in accordance with Chapter 78-34-00 of the Boeing 747
Maintenance Manual, dated April 25, 1998.
Correction Actions
(1) If no discrepancy is detected, repeat the functional test
thereafter at intervals not to exceed 3,000 flight hours.
(2) If any discrepancy is detected, prior to further flight,
repair in accordance with the procedures specified in the Boeing 747
Maintenance Manual. Additionally, prior to further flight, the
functional test must be successfully accomplished. Repeat the
functional test thereafter at intervals not to exceed 3,000 flight
hours.
Spares
(f) If, after incorporation of the modification required by
paragraph (d) of this AD on any airplane, it becomes necessary to
install a thrust reverser assembly that does not have the TRAS locks
installed, dispatch of the airplane is allowed in accordance with
the provisions and limitations specified in the operator's FAA-
approved Master Minimum Equipment List, provided that the thrust
reverser assembly that does not have the TRAS locks installed is
deactivated in accordance with Section 78-1 of Boeing Document D6-
33391, ``Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures
Guide,'' Revision 22, dated January 30, 1998. No more than one
thrust reverser on any airplane may be deactivated under the
provisions of this paragraph. Within 10 days after deactivation of
the thrust reverser, install a thrust reverser assembly that has the
TRAS locks installed and reactivate the thrust reverser.
(g) If, prior to incorporation of the modification required by
paragraph (d) of this AD on any airplane, it becomes necessary to
install a thrust reverser assembly that has the TRAS locks
installed, dispatch of the airplane is allowed in accordance with
the provisions and limitations specified in the operator's FAA-
approved Master Minimum Equipment List, provided that the thrust
reverser assembly that has the TRAS locks installed is deactivated
in accordance with Section 78-1 of Boeing Document D6-33391,
``Boeing 747-100/-200/-300/SP Dispatch Deviations Procedures
Guide,'' Revision 22, dated January 30, 1998. No more than one
thrust reverser on any airplane may
[[Page 57806]]
be deactivated under the provisions of this paragraph. Within 10
days after deactivation of the thrust reverser, install a thrust
reverser assembly that does not have the TRAS locks installed and
reactivate the thrust reverser.
Alternative Methods of Compliance
(h) 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 5: 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
Sec. Sec. 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 October 21, 1999.
D. L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-28084 Filed 10-26-99; 8:45 am]
BILLING CODE 4910-13-P