[Federal Register Volume 62, Number 26 (Friday, February 7, 1997)]
[Rules and Regulations]
[Pages 5746-5748]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-2675]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-148-AD; Amendment 39-9919; AD 97-03-14]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-300 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 series airplanes, that 
requires an inspection to detect fatigue cracking, base trim, and upper 
flange over-trim of the pulley brackets of the aileron control cables. 
This amendment also requires, if necessary, replacement of the pulley 
brackets with new pulley brackets, and replacement of the two button-
head rivets with flush-head rivets. This amendment is prompted by a 
review of the design of the flight control systems on Model 737 series 
airplanes. The actions specified by this AD are intended to prevent 
fatigue cracking or fracturing of the pulley brackets, which could 
result in slack in the cables and consequent reduced ability of the 
flightcrew to control the aileron.

DATES: Effective March 14, 1997.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 14, 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: Don Kurle, Senior Engineer, Systems 
and Equipment Branch, ANM-130S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (206) 227-2798; 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 
series airplanes was published in the Federal Register on August 28, 
1996 (61 FR 44237). That action proposed to require a visual inspection 
to detect fatigue cracking, base trim, and upper flange over-trim of 
the pulley brackets of the aileron control cables. That action also 
proposed to require, if necessary, replacement of the pulley brackets 
with new pulley brackets, and replacement of the two button-head rivets 
with flush-head rivets.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Support for the Proposal

    One commenter supports the proposed rule.

Request To Revise Statement of Findings of Critical Design Review Team

    One commenter requests the second paragraph of the Discussion 
section that appeared in the preamble to the proposed rule be revised 
to accurately reflect the findings of the Critical Design Review (CDR) 
team. The commenter asks that the FAA delete the one sentence in that 
paragraph, which read: ``The recommendations of the team include 
various changes to the design of the flight control systems of these 
airplanes, as well as correction of certain design deficiencies.'' The 
commenter suggests that the following sentences should be added: ``The 
team did not find any design issues that could lead to a definite cause 
of the accidents that gave rise to this effort. The recommendations of 
the team include various changes to the design of the flight control 
systems of these airplanes, as well as incorporation of certain design 
improvements in order to enhance its already acceptable level of 
safety.''
    The FAA does not find that a revision to this final rule in the 
manner suggested by the commenter is necessary, since the Discussion 
section of a proposed rule does not reappear in a final rule. The FAA 
acknowledges that the CDR team did not find any design issue that could 
lead to a definite cause of the accidents that gave rise to this 
effort. However, as a result of having conducted the CDR of the flight 
control systems on Boeing Model 737 series airplanes, the team 
indicated that there are a number of recommendations that should be 
addressed by the FAA for each of the various models of the Model 737.

Request To Extend Compliance Time

    The Air Transport Association (ATA) of America, on behalf of one of 
its members, requests that the proposed compliance time be extended 
from 18 months to four years. The ATA member indicates that the 
consequences of bracket failure are minimal since a dual control path 
exists. The commenter adds that, even in the event of total cable input 
failure on one side of the control path, control of the aircraft would 
not be lost. The commenter points out that the referenced service 
bulletin states that resultant cable slack will cause sluggish aileron 
control, which should be apparent to the flightcrew in the event of 
failure of a bracket. The commenter also states that the adoption of an 
18-month compliance time would pose an unnecessary burden on operators, 
and that a compliance time of four years is adequate to address the 
unsafe condition. The ATA states that it does not view the identified 
unsafe condition as an airworthiness concern. However, in the interest 
of enhancing safety, the ATA requests that the rule be adopted with the 
extended compliance time.
    The FAA does not concur. The FAA acknowledges that a dual control 
path exists, and that in the event of failure of a bracket, the second 
load path will

[[Page 5747]]

allow operation of the aileron. However, under heavy flightcrew 
workload conditions, the ability of the flightcrew to control the 
airplane would be reduced; the FAA has determined that this poses a 
potential unsafe condition that must be corrected in a timely manner.
    In developing an appropriate compliance time for the proposed 
inspection, the FAAs' intent is that it be performed during a regularly 
scheduled maintenance visit for the majority of the affected fleet when 
the airplanes would be located at a base where special equipment and 
trained personnel would be readily available, if necessary. The FAA 
finds that 18 months corresponds closely to the interval representative 
of most of the affected operators' normal maintenance schedules. 
Additionally, since the service bulletin cited in this AD was issued in 
1988, the FAA anticipates that a majority of the pulley brackets and 
rivets that require replacement have already been replaced. Finally, in 
light of the fact that the required actions take only one work hour per 
airplane to accomplish, the FAA is puzzled by the commenter's assertion 
that the 18-month compliance time imposes an ``unnecessary burden'' on 
affected operations. The FAA considers that an 18-month compliance time 
is appropriate and will provide an acceptable level of safety.

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 as proposed.

Cost Impact

    There are approximately 262 Model 737-300 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 169 
airplanes of U.S. registry will be affected by this AD, that it will 
take approximately 1 work hour 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 $10,140, or $60 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.
    Should an operator be required to accomplish the replacement of 
pulley brackets and rivets, it will take approximately 15 work hours 
per airplane to accomplish those actions, at an average labor rate of 
$60 per work hour. Required parts will cost approximately $713 per 
airplane. Based on these figures, the cost impact of any necessary 
replacement action is estimated to be $1,613 per airplane.

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:

97-03-14 Boeing: Amendment 39-9919. Docket 96-NM-148-AD.

    Applicability: Model 737-300 series airplanes; as listed in 
Boeing Service Bulletin 737-27-1154, dated August 25, 1988; 
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 (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 fatigue cracking or fracturing of the pulley 
brackets, which could result in slack in the cables and consequent 
reduced ability of the flightcrew to control the aileron, accomplish 
the following:
    (a) Within 18 months after the effective date of this AD: 
Perform a visual inspection to detect fatigue cracking, base trim, 
or upper flange over-trim of the pulley brackets, part number (P/N) 
65C25555-3, 65C25555-501, or 69-73479-1, of the aileron control 
cables, in accordance with Boeing Service Bulletin 737-27-1154, 
dated August 25, 1988.
    (b) If any cracking or over-trim of the pulley brackets is 
detected: Prior to further flight, replace the pulley brackets with 
new pulley brackets; and replace the two existing button-head rivets 
with flush-head rivets; in accordance with Boeing Service Bulletin 
737-27-1154, dated August 25, 1988.
    (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 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (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.
    (e) The inspection and replacement shall be done in accordance 
with Boeing Service Bulletin 737-27-1154, dated August 25, 1988. 
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.
    (f) This amendment becomes effective on March 14, 1997.


[[Page 5748]]


    Issued in Renton, Washington, on January 29, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-2675 Filed 2-6-97; 8:45 am]
BILLING CODE 4910-13-P