[Federal Register Volume 60, Number 92 (Friday, May 12, 1995)]
[Rules and Regulations]
[Pages 25606-25608]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-11354]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 94-NM-198-AD; Amendment 39-9222; AD 95-10-05]


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 replacement of the horizontal stabilizer trim 
electric actuator. This amendment is prompted by reports of a binding 
condition in the clutch disk in the horizontal stabilizer trim electric 
actuator. The actions specified by this AD are intended to prevent 
reduced controllability of the airplane due to binding of a clutch disk 
in the horizontal stabilizer trim electric actuator.

DATES: Effective June 12, 1995.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of June 12, 1995.

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: Kenneth W. Frey, Aerospace Engineer, 
Systems and Equipment Branch, ANM- [[Page 25607]] 132S, FAA, Transport 
Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind 
Avenue, SW., Renton, Washington 98055-4056; 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 
November 22, 1994 (59 FR 60095). That action proposed to require 
replacement of the horizontal stabilizer trim electric actuator.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    One commenter requests that the proposed compliance time of 12 
months for replacement of the actuator be extended to 18 months. The 
commenter states that timely accomplishment of the replacement is 
dependent upon the ability of BFGoodrich to quickly rework and return a 
fixed number of rotable actuator units. BFGoodrich has indicated that 
``loaner units'' are not available, and that the initial retrofit/
production units of the newer configuration will not be available to 
affected operators in time to allow replacement within the proposed 
compliance interval. Consequently, retrofit cannot be easily 
accelerated unless more rotable units are made available.
    The FAA does not concur with the commenter's request to extend the 
compliance time for replacement. The FAA has been advised by Boeing 
that 75 loaner units have been made available to operators since the 
end of March 1995. These units are being manufactured to support the 
compliance time of this AD. (Boeing has advised that operators should 
contact Boeing Customer Service to arrange for delivery of loaner 
units.) In addition, the FAA has been advised that some operators have 
several spare units in-house which can be used as rotable units during 
the compliance period for the modification. In consideration of these 
factors, the FAA has determined that an extension of the compliance 
time is not warranted.
    Two commenters request that the compliance time of proposed 
paragraph (b) be revised to allow installation of the unmodified 
actuators (having part number 10-62033-3) for a longer period of time 
after the effective date of the final rule. One of these commenters 
states that the inability to obtain spare units will be most severe in 
the early stages of the proposed retrofit; without more time to provide 
for spare modified units in the fleet, there is a high likelihood that 
airplanes could be grounded due to lack of airworthy parts. The other 
commenter states that the current operational procedures provide 
background information on stabilizer trim coasting, and that the 
current runaway stabilizer procedures in the Abnormal Procedures 
section of the Airplane Flight Manual effectively inhibit and limit an 
out-of-trim condition. In light of this, the commenter considers that 
the safety of flight would not be compromised by extending the 
compliance period by an additional 6 months.
    The FAA concurs with the commenters' request. Although, as 
explained above, the FAA is confident that enough modified units will 
be available to all affected operators for replacement within the 12-
month compliance time, there is a possibility that a modified unit may 
not be available, for example, in a situation where replacement is 
necessary and the airplane is in a remote location. For this reason, 
and the fact that adequate operational procedures are currently 
available to address potential out-of-trim conditions, the FAA 
considers that allowing unmodified units to be installed for a period 
up to 6 months after the effective date of the rule will not adversely 
affect safety. Such an extension also will ensure that no affected 
airplane will be grounded unnecessarily due to the unavailability of 
required parts. Accordingly, paragraph (b) of the final rule has been 
revised to allow installation of unmodified parts for 6 months after 
the effective date.
    One commenter requests that issuance of the final rule be delayed 
until a new electric motor assembly and accompanying service document 
is developed and available from the airframe manufacturer. This 
commenter states that the planned new assembly will do the tasks of the 
autopilot stabilizer trim servo and the stabilizer trim electric 
actuator; the motor does not incorporate directional clutches.
    The FAA does not concur with the commenter's request to delay the 
rule. Delaying this action until after the release of the 
manufacturer's planned modification and service document is 
unwarranted, since parts are available at this time to address the 
unsafe condition within the compliance interval. However, the FAA may 
consider additional rulemaking once the new modification is developed, 
approved, and available.
    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.
    There are approximately 1,448 Model 737-300, -400, and -500 series 
airplanes of the affected design in the worldwide fleet. The FAA 
estimates that 590 airplanes of U.S. registry will be affected by this 
proposed AD. Accomplishment of the required replacement of the 
stabilizer trim actuator will take approximately 4 work hours per 
airplane, at an average labor rate of $60 per work hour. The cost of 
required parts is approximately $600 per airplane. Based on these 
figures, the total cost impact of the AD on U.S. operators is estimated 
to be $495,600, or $840 per airplane.
    The total 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.
    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. [[Page 25608]] 

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. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

95-10-05  Boeing: Amendment 39-9222. Docket 94-NM-198-AD.

    Applicability: Model 737-300, -400, and -500 series airplanes; 
as listed in Boeing Alert Service Bulletin 737-27A1191, Revision 1, 
dated November 3, 1994; certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
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 use the authority 
provided in paragraph (c) to request approval from the FAA. This 
approval may address either no action, if the current configuration 
eliminates the unsafe condition; or different actions necessary to 
address the unsafe condition described in this AD. Such a request 
should include an assessment of the effect of the changed 
configuration on the unsafe condition addressed by this AD. In no 
case does the presence of any modification, alteration, or repair 
remove any airplane from the applicability of this AD.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent reduced controllability of the airplane, accomplish 
the following:
    (a) Within 12 months after the effective date of this AD, 
replace the horizontal stabilizer trim electric actuator having part 
number 10-62033-3 with one that has been modified and re-identified 
as P/N 10-62033-4, in accordance with Boeing Alert Service Bulletin 
737-27A1191, Revision 1, dated November 3, 1994.
    (b) As of a date 6 months after the effective date of this AD, 
no person shall install a horizontal stabilizer trim electric 
actuator having part number 10-62033-3 on any airplane.
    (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 
Secs. 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 replacement shall be done in accordance with Boeing 
Alert Service Bulletin 737-27A1191, Revision 1, dated November 3, 
1994. 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 June 12, 1995.

    Issued in Renton, Washington, on May 3, 1995.
James V. Devany,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-11354 Filed 5-11-95; 8:45 am]
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