[Federal Register Volume 64, Number 44 (Monday, March 8, 1999)]
[Rules and Regulations]
[Pages 10935-10937]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-5432]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-09-AD; Amendment 39-11063; AD 99-05-15]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, -200C, -
300, -400, and -500 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to certain Boeing Model 737-100, -200, -200C, -300, -400, 
and -500 series airplanes. This action requires a one-time inspection 
of the attachment nuts at each end attachment of the elevator tab push 
rods to measure run-on torque values, and corrective actions, if 
necessary. This amendment is prompted by reports of excessive high-
frequency airframe vibration during flight, with consequent structural 
damage to the elevator tab, elevator, and stabilizer. The actions 
specified in this AD are intended to prevent detachment of an elevator 
tab push rod due to a detached nut at either end attachment of a push 
rod, which could result in excessive high-frequency airframe vibration 
during flight; consequent structural damage to the elevator tab, 
elevator, and horizontal stabilizer; and reduced controllability of the 
airplane.

DATES: Effective March 23, 1999.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 23, 1999.
    Comments for inclusion in the Rules Docket must be received on or 
before May 7, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-09-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056.
    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 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.

FOR FURTHER INFORMATION CONTACT: Greg Schneider, Aerospace Engineer, 
Airframe Branch, ANM-120S; FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-2028; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: The FAA has received two reports indicating 
that excessive high-frequency airframe vibration occurred during flight 
on Boeing Model 737-200 and 737-300 series airplanes, which resulted in 
severe damage to the elevator, elevator tab, and elevator tab control 
mechanism. One report indicated that the source of the vibration was 
due to a detached elevator tab push rod that resulted from a missing or 
detached end attachment nut. The other report indicated that the 
initial source of vibration was a missing end bearing on an elevator 
tab push rod.
    The FAA also has reviewed the results of inspections that were 
accomplished in accordance with Boeing Alert Service Bulletin 737-
27A1205, dated August 28, 1997, and Boeing All-Base Telex M-7272-97-
0897, dated February 13, 1997. Findings revealed that after 478 
airplanes were inspected, 3 loose end attachment nuts and 7.9 per cent 
of all end attachment nuts inspected (a total of 2,278 nuts) did not 
have adequate run-on torque. These findings indicate that the 
occurrence of inadequate run-on and seating torque values of the end 
attachment nuts of the elevator tab push rods is not an isolated event.
    The FAA has determined from these reports that, if an end 
attachment nut of an elevator tab push rod is removed and

[[Page 10936]]

reinstalled during routine or non-routine maintenance, the self-locking 
capability (run-on torque) of the nut may become degraded. If an end 
attachment nut having inadequate run-on torque has been installed on an 
airplane, the likelihood of the nut becoming loose is increased 
significantly. The same is true for a nut having a seating torque with 
less than the minimum value specified in the alert service bulletin.
    Inadequate run-on and/or seating torque values of an attachment nut 
at either end of an elevator tab push rod, if not corrected, could 
result in a nut becoming detached from an end attachment bolt of a push 
rod, which could cause excessive high-frequency vibration during 
flight. Such vibration could result in structural damage to the 
elevator tab, elevator, and horizontal stabilizer; and result in 
reduced controllability of the airplane.

Explanation of Relevant Service Information

    The FAA has reviewed and approved the previously referenced alert 
service bulletin, which describes procedures for a one-time inspection 
of the attachment nuts at each end of each elevator tab push rod to 
measure run-on torque values, and corrective actions, if necessary. 
Corrective actions include the replacement of any end attachment nut 
that is outside the run-on torque values specified in the alert service 
bulletin with a new nut, and ensuring that the final seating torque of 
the nuts is within the limits specified in the alert service bulletin.
    The FAA also has reviewed and approved Boeing Service Letter 737-
SL-27-118-A, dated November 14, 1997, which describes procedures for 
the replacement of the existing bolts and nuts at each end of the push 
rods with new bolts and nuts that incorporate the installation of 
cotter pins as a secondary locking feature. This new bolt, nut, and 
cotter pin design provides an additional level of safety in preventing 
detachment of an end attachment nut, which could result in detachment 
of an elevator tab push rod.

Explanation of the Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other Boeing Model 737-100, -200, -200C, -300, -
400, and -500 series airplanes of the same type design, this AD is 
being issued to prevent detachment of the elevator tab push rod due to 
a detached nut at either end attachment of a push rod, which could 
result in excessive high-frequency airframe vibration during flight; 
consequent structural damage to the elevator tab, elevator, and 
horizontal stabilizer; and reduced controllability of the airplane. 
This AD requires accomplishment of actions specified in the alert 
service bulletin and the service letter described previously, except as 
discussed below.

Differences Between the Alert Service Bulletin and This AD

    Operators should note that, although the effectivity listing in the 
Summary of the alert service bulletin specifies ``all 737 airplanes 
line positions 1 through 2892,'' the applicability statement of this AD 
specifies ``Model 737-100, -200, -200C, -300, -400, and -500 series 
airplanes, line numbers 1 through 2939 inclusive.'' The FAA points out 
that, at the time of issuance of the alert service bulletin, ``all 737 
airplanes'' only included Model 737-100 through -500 series airplanes. 
The FAA has determined that the use of ``line numbers'' rather than 
``line positions'' is the more appropriate term. The FAA also has 
determined that it is necessary to include the line numbers 2893 
through 2939 in the applicability of this AD because those additional 
airplanes are subject to the same unsafe condition as the airplanes 
specified in the alert service bulletin.
    Operators also should note that the alert service bulletin 
specifies replacement of any end attachment nut that is outside the 
run-on torque values specified in the alert service bulletin with a new 
nut. However, if the run-on torque value of any end attachment nut is 
outside the limits specified in the alert service bulletin, paragraph 
(a)(2) of this AD requires replacement of all existing attachment nuts 
at each end of each elevator tab push rod with new bolts and self-
locking castellated nuts that have cotter pins installed as a secondary 
locking feature. The FAA has determined that such a replacement 
provides an additional level of safety in preventing detachment of an 
end attachment nut, which could result in detachment of an elevator tab 
push rod.
    Operators also should note that the alert service bulletin 
recommends that the one-time inspection to measure run-on torque values 
of the attachment nuts at each end attachment of the elevator tab push 
rods be accomplished at the next scheduled elevator tab maintenance 
work. However, this AD requires that the inspection be accomplished 
within 90 days after the effective date of this AD. In developing an 
appropriate compliance time for this AD, the FAA considered not only 
the degree of urgency associated with addressing the subject unsafe 
condition, but the average utilization of the affected fleet and the 
time necessary to perform the inspection (4 hours). In light of all of 
these factors, the FAA finds that a 90-day compliance time for 
initiating the required actions is warranted, in that it represents an 
appropriate interval of time allowable for affected airplanes to 
continue to operate without compromising safety.

Interim Action

    This AD is considered to be interim action until final action is 
identified, at which time the FAA may consider further rulemaking, 
which could include replacement of the existing bolts and nuts at each 
end of the push rods with new bolts and self-locking castellated nuts 
that have cotter pins installed.

Determination of Rule's Effective Date

    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.

[[Page 10937]]

    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 99-NM-09-AD.'' The postcard will be date stamped and 
returned to the commenter.

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.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, 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:

99-05-15  Boeing: Amendment 39-11063. Docket 99-NM-09-AD.

    Applicability: Model 737-100, -200, -200C, -300, -400, and -500 
series airplanes; line numbers 1 through 2939 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 
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 detachment of an elevator tab push rod due to a 
detached nut at either end attachment of a push rod, which could 
result in excessive high-frequency airframe vibration during flight; 
consequent structural damage to the elevator tab, elevator, and 
horizontal stabilizer; and reduced controllability of the airplane; 
accomplish the following:
    (a) Within 90 days after the effective date of this AD, perform 
a one-time inspection of all attachment nuts at each end of each 
elevator tab push rod to measure the run-on torque values of the 
nuts, in accordance with Boeing Alert Service Bulletin 737-27A1205, 
dated August 28, 1997.
    (1) If the run-on torque value of any end attachment nut is 
within the limits specified in the alert service bulletin, prior to 
further flight, ensure that the final seating torque of the 
attachment nuts is within the torque values specified in the alert 
service bulletin.
    (2) If the run-on torque value of any end attachment nut is 
outside the limits specified in the alert service bulletin, prior to 
further flight, replace all existing bolts and attachment nuts at 
each end of each elevator tab push rod with new bolts and self-
locking castellated nuts that have cotter pins installed as a 
secondary locking feature in accordance with Boeing Service Letter 
737-SL-27-118-A, dated November 14, 1997, and ensure that the final 
seating torque of the nuts is within the torque values specified in 
the service letter.

    Note 2: Accomplishment of the inspection and ensuring adequate 
final seating torque values, prior to the effective date of this AD, 
in accordance with Boeing All-Base Telex M-7272-97-0897, dated 
February 13, 1997, are considered acceptable for compliance with the 
actions specified in paragraphs (a) and (a)(1) of this AD for only 
the forward attachment nuts.

    (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 3: 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 737-27A1205, dated August 28, 1997, and Boeing 
Service Letter 737-SL-27-118-A, dated November 14, 1997. 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 23, 1999.

    Issued in Renton, Washington, on February 26, 1999.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-5432 Filed 3-5-99; 8:45 am]
BILLING CODE 4910-13-U