[Federal Register Volume 64, Number 162 (Monday, August 23, 1999)]
[Proposed Rules]
[Pages 45927-45929]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-21846]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NM-101-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 757 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
-----------------------------------------------------------------------
SUMMARY: This document proposes the adoption of a new airworthiness
directive (AD) that is applicable to certain Boeing Model 757 series
airplanes. This proposal would require a modification of the reverse
thrust lever assemblies and replacement of the spring bumper assemblies
of the thrust reverser sleeves with new assemblies. This proposal is
prompted by an FAA review of the thrust reverser system on all
transport category airplanes including the Boeing Model 757 series
airplane. The actions specified by the proposed AD are intended to
prevent operation with an energized sync lock or malfunctioning sleeve
locking devices, which could result in the deployment of a thrust
reverser in flight and subsequent reduced controllability of the
airplane.
DATES: Comments must be received by October 7, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 99-NM-101-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: Kathrine Rask, Aerospace Engineer,
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate,
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (425) 227-1547; 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
[[Page 45928]]
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-101-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-101-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
Following a 1991 accident caused by deployment of a thrust reverser
in flight on a Boeing Model 767 series airplane, the FAA initiated a
special certification review of all transport category thrust reverser
systems and airplane controllability in the event of deployment of a
thrust reverser in flight. As a result of that review, Boeing
developed, for certain Boeing airplane models, an additional thrust
reverser locking system and conducted a safety assessment to determine
the probability of deployment of a thrust reverser in flight. The
safety assessment evaluates every possible combination of failures for
the thrust reverser system that could result in deployment of a thrust
reverser in flight, and considers the probability and detectability of
each failure. The safety assessment for the Model 757 series airplane
identified two failure conditions that, because they are latent
failures, would significantly affect the reliability of the thrust
reverser locking system and, in combination with other failures in the
thrust reverser system, could result in deployment of a thrust reverser
in flight and subsequent reduced controllability of the airplane. The
two failure conditions are described below.
Failure of the reverse thrust switch actuator causes the
switch to remain in a powered position. The failure causes the thrust
reverser sync lock to remain energized while the airplane is operated
on the ground, during the takeoff roll, and possibly during the first
two minutes of flight. This failure would not prevent normal operation
of the thrust reverser; however, it would not be detected until the
next sync lock integrity test was conducted.
The spring bumper assembly pushes on the thrust reverser
translating sleeve causing adequate sleeve movement, if the sleeve is
unlocked, to activate the auto-restow system in flight or provide a
visual indication of an unlocked sleeve during the ground walk-around
inspection. If the spring bumper assembly fails, it is likely that a
malfunctioning sleeve locking device would not be detected for several
flight cycles.
Should either of these failure conditions occur but remain
undetected for an extended period, in the event of other failures in
the thrust reverser system, the thrust reverser locking systems may not
prevent deployment of a thrust reverser in flight.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Service Bulletin 757-76-
0009, Revision 1, dated December 3, 1998, which describes procedures
for a modification of the reverse thrust lever assemblies. This
modification improves the reliability of the reverse thrust switch and
changes the failed state of the switch, such that failure of the
reverse thrust switch actuator does not result in latching of the relay
and consequent energizing of the sync lock or opening of the isolation
valve.
The FAA has also reviewed and approved Boeing Service Bulletin 757-
78-0012, dated August 31, 1989, which describes procedures for
replacement of the spring bumper assembly of the thrust reverser sleeve
with a new spring bumper assembly with an improved service life. Such
replacement ensures that a malfunctioning sleeve locking device will be
detected within one flight cycle.
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 require accomplishment of the actions specified in
the service bulletins described previously.
Explanation of Applicability
Certain airplanes listed in Boeing Service Bulletin 757-76-0009,
Revision 1, may not need to be modified in accordance with that service
bulletin. Certain Model 757 series airplanes powered by Pratt and
Whitney Model PW2000 engines that are affected by Boeing Service
Bulletin 757-76-0009, Revision 1, were delivered with reverse thrust
switches that open the thrust reverser hydraulic isolation valves. On
these airplanes, failure of the reverse thrust switch actuator causes
the hydraulic isolation valve to remain open while the airplane is on
the ground and during the takeoff roll. Such a failure would be
detected through various engine indicating and crew alerting system
(EICAS) messages within one flight. Therefore, because the failure
would not go undetected for an extended period, the reliability of the
thrust reverser locking system is not significantly affected, no unsafe
condition exists, and these airplanes are not subject to the
modification described in Boeing Service Bulletin 757-76-0009, Revision
1.
Certain other Model 757 series airplanes powered by Pratt and
Whitney Model PW2000 engines that are affected by Boeing Service
Bulletin 757-76-0009, Revision 1, have a redesigned switch function
arrangement on which the reverse thrust switches energize the sync
locks. (This redesign transfers control of the hydraulic isolation
valve from the reverse thrust switches to the autothrottle switchpack
switches.) On these airplanes, failure of the reverse thrust switch
actuator causes the reverse thrust switch to remain in a powered
position, which results in the thrust reverser sync lock remaining
energized while the airplane is on the ground. Because there is no
indication of such a failure, except from the sync lock integrity test,
these airplanes would therefore be subject to the unsafe condition
described previously.
The FAA knows of operators of Boeing Model 757 series airplanes
powered by Pratt and Whitney Model PW2000 engines that have
incorporated the redesigned switch function arrangement. However, the
FAA cannot define the extent of incorporation of this modification in
the affected fleet; therefore, this proposed AD is applicable to all
airplanes listed in Boeing Service Bulletin 757-76-0009, Revision 1 (in
addition to those listed in Boeing Service Bulletin 757-78-0012). If an
operator of Boeing Model 757 series airplanes powered by Pratt and
Whitney Model PW2000 engines can determine that the reverse thrust
switches, as defined in Boeing Service Bulletin 757-76-0009, Revision
1, open the thrust reverser hydraulic isolation valves, that operator
may request an alternative method of compliance in
[[Page 45929]]
accordance with paragraph (c) of this proposed AD.
Cost Impact
There are approximately 308 airplanes of the affected design in the
worldwide fleet.
The FAA estimates that the proposed modification of the reverse
thrust lever assemblies would be required to be accomplished on 169
U.S. registered airplanes. It would take approximately 8 work hours per
airplane to accomplish the proposed modification at an average labor
rate of $60 per work hour. Required parts would cost approximately $29
per airplane. Based on these figures, the cost impact of this proposed
modification on U.S. operators is estimated to be $86,021, or $509 per
airplane.
The FAA estimates that the proposed replacement of the spring
bumper assemblies would be required to be accomplished on 92 U.S.
registered airplanes. It would take approximately 10 work hours per
airplane to accomplish the proposed replacement at an average labor
rate of $60 per work hour. Required parts would cost approximately
$5,178 per airplane. Based on these figures, the cost impact of this
proposed replacement on U.S. operators is estimated to be $531,576, or
$5,778 per airplane.
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.
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-101-AD.
Applicability: Model 757 series airplanes, as listed in Boeing
Service Bulletin 757-76-0009, Revision 1, dated December 3, 1998, or
Boeing Service Bulletin 757-78-0012, dated August 31, 1989;
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 (c) 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 prevent operation with an energized sync lock or
malfunctioning sleeve locking devices, which could result in
deployment of a thrust reverser in flight and subsequent reduced
controllability of the airplane, accomplish the following:
(a) For airplanes listed in Boeing Service Bulletin 757-76-0009,
Revision 1, dated December 3, 1998: Within 2 years after the
effective date of the AD, replace the reverse thrust switches and
actuators with improved switches and actuators, and modify the
reverse lever links and thrust control levers in accordance with the
service bulletin.
Note 2: Modifications accomplished prior to the effective date
of this AD in accordance with Boeing Service Bulletin 757-76-0009,
dated November 8, 1990, are considered acceptable for compliance
with the applicable action specified in this amendment.
(b) For airplanes listed in Boeing Service Bulletin 757-78-0012,
dated August 31, 1989: Within 2 years after the effective date of
the AD, replace the spring bumper assemblies of the thrust reverser
sleeve with improved assemblies in accordance with the service
bulletin.
Alternative Methods of Compliance
(c) An alternative method of compliance or adjustment of the
compliance time that provides an acceptable level of safety may be
used if approved by the Manager, Seattle Aircraft Certification
Office (ACO), FAA, Transport Airplane Directorate. Operators shall
submit their requests through an appropriate FAA Principal
Maintenance Inspector, who may add comments and then send it to the
Manager, Seattle ACO.
Note 3: 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
(d) 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 August 17, 1999.
D. L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-21846 Filed 8-20-99; 8:45 am]
BILLING CODE 4910-13-P
