[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]


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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).

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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

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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

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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