[Federal Register Volume 62, Number 18 (Tuesday, January 28, 1997)]
[Rules and Regulations]
[Pages 3993-3994]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-1478]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-156-AD; Amendment 39-9901; AD 97-02-16]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-300, -400, and -500 
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 737-300, -400, and -500 series 
airplanes, that requires modification of the system that detects a loss 
of tension in the cable controlling the flaps by removing the shim from 
behind the proximity switch and by trimming the switch bracket. This 
amendment is prompted by reports that the switch bracket can impair the 
movement of a pulley arm mechanism, ultimately preventing the detection 
system from operating. The actions specified by this AD are intended to 
prevent such impairment, which could result in movement of the flaps 
without action by the pilot, and ultimately cause reduced 
controllability of the airplane.

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: Ken Frey, Aerospace Engineer, Systems 
and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification 
Office, 1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-
2673; 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 737-300, -
400, and -500 series airplanes was published in the Federal Register on 
September 13, 1996 (61 FR 48435). That action proposed to require 
removal of the shim behind the proximity switch, if installed; and 
trimming of the bracket for the proximity switch.
    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 Extend Compliance Time

    One commenter requests that the compliance time for accomplishment 
of the modification be extended from the proposed ``3,200 flight hours 
or 18 months'' to ``4,600 flight hours or 24 months,'' whichever occurs 
first after the effective date of the AD. The commenter states that the 
modification is time-consuming to perform, and the requested extension 
of the compliance time would allow affected operators to accomplish it 
during regularly scheduled maintenance (``C'' check).
    The FAA does not concur. In developing an appropriate compliance 
time for this action, the FAA considered not only the degree of urgency 
associated with addressing the subject unsafe condition, but the 
availability of required parts and the practical aspect of installing 
the required modification within an interval of time that parallels 
normal scheduled maintenance for the majority of affected operators. 
The FAA finds that the compliance time, as proposed, represents the 
average ``C'' check maintenance interval for the majority of affected 
operators. Additionally, the FAA does not consider the modification to 
be especially time-consuming, since it takes only 7 work hours per 
airplane to perform, and does not entail the need for special tools or 
parts. In light of these items, the FAA finds the proposed compliance 
time to be appropriate. However, under the provisions of paragraph (b) 
of the final rule, the FAA may approve requests for adjustments to the 
compliance time if data are submitted to substantiate that such an 
adjustment would provide an acceptable level of safety.

Request To Clarify Description of Required Actions

    One commenter requests that the description of the requirement 
modification of the flap control cable failure detection system be 
clarified. The commenter points out that the shim to be removed is 
located behind the proximity switch, rather than behind the bracket for 
the proximity switch, as was stated in the proposal. Additionally, the 
commenter suggests that the required action would be clearer if stated 
as, ``trimming of the switch bracket,'' rather than ``trimming of the 
bracket of the proximity switch.''
    The FAA concurs that the commenter's suggested changes to the 
description of the required actions would make the AD clearer. The FAA 
has made those changes throughout this final rule in the appropriate 
places.

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 1,619 Model 737-300, -400, and -500 series 
airplanes of the affected design in the worldwide fleet. The FAA 
estimates that 685 airplanes of U.S. registry will be affected by this 
AD, that it will take approximately 7 work hours per airplane to 
accomplish the required actions, and that the average labor rate is $60 
per work hour. Based on these figures, the cost impact of the AD on 
U.S. operators is estimated to be $287,700, or $420 per airplane.

[[Page 3994]]

    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:

    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:

97-02-16 Boeing: Amendment 39-9901. Docket 96-NM-156-AD.
    Applicability: Model 737-300, -400 and -500 series airplanes 
having line production numbers 1001 through 2765, 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 movement of the flaps from their last set position 
without action by the pilot, which could reduce controllability of 
the airplane, accomplish the following:
    (a) Within 18 months or 3,200 hours time-in-service after the 
effective date of this AD, whichever occurs first, remove the shim, 
if installed, from behind the proximity switch in the system which 
detects a loss of tension in the cable controlling the flaps; and 
trim the switch bracket; in accordance with Boeing Alert Service 
Bulletin 737-27A1199, dated June 20, 1996.
    (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 actions shall be done in accordance with Boeing Alert 
Service Bulletin 737-27A1199, dated June 20, 1996. 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 15, 1997.
S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-1478 Filed 1-27-97; 8:45 am]
BILLING CODE 4910-13-U