[Federal Register Volume 61, Number 169 (Thursday, August 29, 1996)]
[Proposed Rules]
[Pages 45373-45375]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-22013]
=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 96-NM-125-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 757 and 767 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 and 767
series airplanes. This proposal would require replacement of the thrust
management computer (TMC) with a new TMC. This proposal is prompted by
reports that, due to a defective relay within the TMC, an uncommanded
advancement of the throttle levers occurred. The actions specified by
the proposed AD are intended to prevent an uncommanded runaway of the
autothrottle during flight or ground operations, which could distract
the crew from normal operation of the airplane or lead to an unintended
speed or altitude change.
DATES: Comments must be received by October 7, 1996.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 96-NM-125-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: Forrest Keller, Senior Aerospace
Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft
Certification Office, 1601 Lind Avenue, SW., Renton, Washington;
telephone (206) 227-2790; fax (206) 227-1181.
SUPPLEMENTARY INFORMATION:
Comments Invited
Interested persons are invited to participate in the making of the
[[Page 45374]]
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 96-NM-125-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-103, Attention: Rules
Docket No. 96-NM-125-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
The FAA has received two reports of uncommanded advancement of the
throttle levers on Boeing Model 757 series airplanes. In one of these
incidents, during flight, the flightcrew had to overpower the
autothrottle to control the airspeed of the airplane. In the other
incident, a similiar event occurred while the airplane was on the
ground. In both of these incidents, the throttle levers continued to
advance even though the flightcrew activated the autothrottle
disconnect switch and switched the ARM switch of the mode control panel
(MCP) to the `off' position. Results of testing on the thrust
management computer (TMC) revealed that the cause of the uncommanded
advancement of the autothrottle lever was attributed to a defective
relay within the TMC. This condition, if not corrected, could result in
a runaway of the autothrottle during flight or ground operations, and,
consequently, distract the crew from normal operation of the airplane
or lead to an unintended speed or altitude change.
The TMC of Model 767 series airplanes is similar in design to that
installed on Model 757 series airplanes. Therefore, the FAA has
determined that both of these models may be subject to this same unsafe
condition.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Alert Service Bulletin
757-22A0052, dated May 30, 1996 (for Model 757 series airplanes), and
Boeing Alert Service Bulletin 767-22A0097, dated May 30, 1996 (for
Model 767 series airplanes). These service bulletins describe
procedures for replacement of the TMC with a new TMC in the E1-3 shelf
in the main equipment center. Accomplishment of the replacement will
correct the previous problem with the relay and prevent a runaway
condition of the autothrottle.
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 replacement of the TMC with a new TMC in the
E1-3 shelf in the main equipment center. The actions would be required
to be accomplished in accordance with the service bulletins described
previously.
Cost Impact
There are approximately 1,339 Boeing Model 757 and 767 series
airplanes (716 Model 757 series airplanes and 623 Model 767 series
airplanes) of the affected design in the worldwide fleet. The FAA
estimates that 558 Model 757 and 767 series airplanes (356 Model 757
series airplanes and 202 Model 767 series airplanes) of U.S. registry
would be affected by this proposed AD. The proposed replacement would
take approximately 3 work hours per airplane to accomplish, at an
average labor rate of $60 per work hour. The cost of the required parts
would be nominal. Based on these figures, the cost impact of the
replacement proposed by this AD on U.S. operators is estimated to be
$100,440, or $180 per airplane.
The cost impact figure discussed above is 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 96-NM-125-AD.
Applicability: Model 757 series airplanes, having line positions
001 through 716, inclusive; and Model 767 series airplanes having
line positions 001 through 556 inclusive, 558 through 587 inclusive,
and 589 through 615 inclusive; certificated in any category.
Note 1: This AD applies to each airplane identified in the
preceding applicability provision, regardless of whether it has been
otherwise 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
[[Page 45375]]
of the requirements of this AD is affected, the owner/operator must
request approval for an alternative method of compliance in
accordance with paragraph (b) 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 runaway of the autothrottle during flight or ground
operations, which could distract the crew from normal operation of
the airplane or lead to an unintended speed or altitude change,
accomplish the following:
(a) Within 6 months after the effective date of this AD, replace
the thrust management computer with a new thrust management computer
in the E1-3 shelf in the main equipment center, in accordance with
the Boeing Alert Service Bulletin 757-22A0052, dated May 30, 1996
(for Model 757 series airplanes), or Boeing Alert Service Bulletin
767-22A0097, dated May 30, 1996 (for Model 767 series airplanes), as
applicable.
(b) 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.
(c) 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 22, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 96-22013 Filed 8-28-96; 8:45 am]
BILLING CODE 4910-13-U
