[Federal Register Volume 62, Number 18 (Tuesday, January 28, 1997)]
[Rules and Regulations]
[Pages 3997-3999]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-1617]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-125-AD; Amendment 39-9904; AD 97-02-19]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 757 and 767 Series 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain Boeing Model 757 and 767 series airplanes, that 
requires replacement of the thrust management computer (TMC) with a new 
TMC. This amendment is prompted by reports indicating that an 
uncommanded advancement of the throttle levers occurred; this condition 
was apparently due to a high impedance connection to the excitation 
phase of the servo motor. The actions specified by this AD are intended 
to prevent an uncommanded runaway of the autothrottle during flight or 
ground operations as a result of problems associated with the TMC, 
which could distract the crew from normal operation of the airplane or 
lead to an unintended speed or altitude change.

DATES: Effective March 4, 1997.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 4, 1997.

ADDRESSES: The service information referenced in this AD may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the Federal 
Aviation Administration (FAA), Transport Airplane Directorate, Rules 
Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of 
the Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.

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: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to certain Boeing Model 757 and 767 
series airplanes was published in the Federal Register on August 29, 
1996 (61 FR 45373). That action proposed to require replacement of the 
thrust management computer (TMC) with a new TMC in the main equipment 
center.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Request To Clarify Description of Problem Addressed

    One commenter requests that references in the proposal to the 
problems prompting the AD action be clarified. The commenter points out 
that the ``Discussion'' section of the preamble to the notice makes 
reference to a ``defective relay within the TMC'' as being the cause of 
the uncommanded advancement of the autothrottle lever.

[[Page 3998]]

However, the commenter considers that statement to be inaccurate. 
Instead, the commenter suggests that the statement be changed to 
indicate that the cause is due to ``high impedance connection to the 
excitation phase of the servo motor. The impedance can be internal to 
the TMC or the result of an external condition.''
    The FAA concurs that the commenter's suggested wording is more 
accurate. The pertinent portions of this final rule have been revised 
to incorporate that wording.

Request to Extend Compliance Time

    Several commenters request that the proposal be revised to extend 
the compliance time for the TMC replacement from the proposed 6 months 
to as much as 24 months. These commenters are concerned that there will 
be a problem with the availability of ample parts to retrofit the 
affected U.S. fleet within the proposed compliance time.
    The FAA concurs that the compliance time can be extended somewhat. 
Input from the TMC vendor indicates that there are 1,800 units that 
will need to be modified and the turn-around time for doing that is 45 
days for each unit; based on current production rates, it will be 
logistically impossible for the vendor to meet a 6-month schedule. In 
light of this information, the FAA has determined that the compliance 
time can be extended to 18 months without adversely compromising 
safety. Paragraph (a) of the final rule has been revised accordingly.

Request to Clarify References to E1-3 Shelf

    One commenter, Boeing, points out that the references in the 
proposal to the TMC being located in the ``E1-3 shelf of the main 
equipment center'' are incorrect with regard to the Model 757. Further, 
this commenter states that the Boeing service bulletins referenced in 
the proposal adequately describe the correct replacement instructions 
for TMC's in both the Model 757 and 767, including the location of the 
TMC; therefore, any reference to the specific shelf number is not 
needed. The commenter suggests that those references be deleted from 
the final rule.
    The FAA concurs. To avoid any confusion on the part of affected 
operators, the FAA has deleted all references to the ``E1-3 shelf'' 
from the final rule.

Request to Revise Cost Impact Information

    Several commenters request that the cost impact information, which 
appeared in the preamble to the proposal, be revised. These commenters 
point out that the cost figures presented did not include the per-unit 
modification cost changed by the manufacturer or approved repair 
station for modification of the TMC. One commenter, Lockheed-Martin, 
indicates that some operators, if they have the tooling capability, can 
perform the modification themselves with a $104 kit obtained from the 
TMC manufacturer; Lockheed-Martin charges $1,000 per unit to modify the 
TMC. Other commenters present cost estimates per airplane that range 
from $1,780 to $2,400. Two commenters also factor in the cost of 
purchasing an additional new TMC unit as a ``seed unit'' for 
implementing the change in their fleets, resulting in cost estimates 
ranging from $45,530 to $60,000.
    The FAA concurs that the cost impact information should be revised 
to reflect more up-to-date and accurate information. While any operator 
certainly has the option to purchase new TMC's to meet the intent of 
this AD, the FAA does not consider that to be economically feasible for 
the majority of the affected fleet. However, based on figures provided 
by the commenters, the FAA finds that an appropriate estimate of costs 
is $2,400 per airplane; this represents 3 work hours to replace the 
unit (at an average labor charge of $60 per work hour) and an average 
of $2,220 for the required (modified) replacement parts. The cost 
impact information, below, has been revised accordingly.

Conclusion

    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the changes previously 
described. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.

Cost Impact

    There are approximately 1,339 Boeing Model 757 and 767 series 
airplanes of the affected design in the worldwide fleet; this number 
represents 716 Model 757 series airplanes and 623 Model 767 series 
airplanes. Of the total number, the FAA estimates that 558 airplanes of 
U.S. registry will be affected by this AD; this number represents 356 
Model 757 series airplanes and 202 Model 767 series airplanes.
    The required replacement will take approximately 3 work hours per 
airplane to accomplish, at an average labor rate of $60 per work hour. 
The cost of the required (modified) replacement units would differ 
depending upon whether the operator, airframe manufacturer, repair 
station, or TMC manufacturer performs the modification of the TMC; in 
any case, the FAA estimates that the average cost for these replacement 
units will be $2,220 per airplane. Based on these figures, the cost 
impact of the AD on U.S. operators is estimated to be $1,339,200, or 
$2,400 per airplane.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet accomplished any of the 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 adopted herein will 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 final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it may be obtained 
from the Rules Docket at the location provided under the caption 
ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends 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:


[[Page 3999]]


    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:

97-02-19 Boeing: Amendment 39-9904. 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 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 18 months after the effective date of this AD, 
replace the thrust management computer (TMC) with a new TMC in 
accordance with 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.
    (d) The replacement shall be done in accordance with 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. 
This incorporation by reference was approved by the Director of the 
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 
51. Copies may be obtained from Boeing Commercial Airplane Group, 
P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be 
inspected at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington; or at the Office of the Federal 
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
    (e) This amendment becomes effective on March 4, 1997.

    Issued in Renton, Washington, on January 16, 1997.
S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-1617 Filed 1-27-97; 8:45 am]
BILLING CODE 4910-13-U