[Federal Register Volume 64, Number 232 (Friday, December 3, 1999)]
[Proposed Rules]
[Pages 67807-67810]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-31435]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-69-AD]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration, DOT.


[[Page 67808]]


ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing 
airworthiness directive (AD), applicable to certain Boeing Model 737-
100, -200, -200C, -300, -400, and -500 series airplanes, that currently 
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 action would add a 
requirement to replace all existing bolts and attachment nuts at the 
forward and aft end attachment of each elevator tab push rod with new 
bolts and self-locking castellated nuts with cotter pins. This proposal 
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: Comments must be received by January 18, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-69-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056. Comments may be inspected at this location 
between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal 
holidays.
    The service information referenced in the proposed rule 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.

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:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed 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 above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 99-NM-69-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 99-NM-69-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On February 26, 1999, the FAA issued AD 99-05-15, amendment 39-
11063 (64 FR 10935, March 8, 1999), applicable to certain Boeing Model 
737-100, -200, -200C, -300, -400, and -500 series airplanes, to require 
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. That action was prompted by reports 
of excessive high-frequency airframe vibration during flight, with 
consequent structural damage to the elevator tab, elevator, and 
stabilizer. The requirements of that 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.
    In the preamble to AD 99-05-15, the FAA indicated that the actions 
required by that AD were considered ``interim action'' until final 
action is identified, at which time the FAA may consider further 
rulemaking. Final action has been identified, and the FAA has 
determined that further rulemaking action is indeed necessary; this AD 
follows from that determination.

Actions Since Issuance of Previous Rule

    Based upon a report of airframe vibration which resulted in severe 
damage to the elevator, elevator tab push rods, and elevator tab, the 
FAA has determined that a fastener installation which incorporates a 
secondary locking feature should be installed at the elevator tab push 
rod end attachments. The report indicated that airframe vibration was 
initially caused by the absence of a bushing, which was not installed 
during maintenance, in one of the elevator push rod attachments. Based 
on this finding, it is concluded that vibration may occur as a result 
of a single elevator tab push rod becoming disconnected. In addition, a 
review of numerous reports has revealed that airframe vibration has 
been caused by worn, loose, or missing parts at the elevator tab 
attachments. To positively address the problem with the elevator tab 
push rod end attachments becoming loose, the FAA finds it necessary to 
mandate the new bolt, castellated nut, and cotter pin installation.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would supersede AD 99-05-15 to continue to require a one-
time inspection of the attachment nuts at each end attachment of the 
elevator tab push rods to measure run-on torque values. The proposed AD 
would also require replacement of existing bolt and attachment nuts 
with new bolts and self-locking castellated nuts that incorporate 
cotter pins as a secondary locking feature. The actions would be 
required to be accomplished in accordance with the service information 
described previously in AD 99-05-15, except as discussed below.

Differences Between Proposed Rule and Service Letter

    Operators should note that Boeing Service Letter 737-SL-27-118-A, 
dated November 14, 1997, describes the actions specified by this 
proposed AD as a design improvement that may be accomplished at any 
time by the

[[Page 67809]]

operator. The service letter, therefore, does not provide a recommended 
timeframe for accomplishing the replacement of the existing bolts and 
attachment nuts with new bolts and self-locking castellated nuts that 
incorporate the installation of cotter pins as a secondary locking 
feature. The FAA has determined that an unspecified interval would not 
address the identified unsafe condition in a timely manner. In 
developing an appropriate compliance time for this AD, the FAA 
considered not only the manufacturer's recommendation, but the degree 
of urgency associated with addressing the subject unsafe condition, the 
average utilization of the affected fleet, and the time necessary to 
perform the replacement (4 hours). In light of all of these factors, 
the FAA finds a 12-month compliance time for completing the required 
actions to be warranted, in that it represents an appropriate interval 
of time allowable for affected airplanes to continue to operate without 
compromising safety.

Cost Impact

    There are approximately 2,742 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 1,106 airplanes of U.S. 
registry would be affected by this proposed AD.
    The new replacement that is proposed in this AD action would take 
approximately 4 work hours per airplane to accomplish, at an average 
labor rate of $60 per work hour. Required parts would cost 
approximately $560 per airplane. Based on these figures, the cost 
impact of the proposed requirements of this AD on U.S. operators is 
estimated to be $884,800, or $800 per airplane.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet accomplished any of the current or proposed 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this AD were not adopted.
    The one-time inspection required by AD 99-05-15 was required to be 
accomplished within 90 days after the effective date of that AD (March 
23, 1999). Since the 90-day compliance time has past, the FAA assumes 
that all airplanes currently on the U.S. Register have been inspected. 
Therefore, there is no future cost impact of this requirement on 
current U.S. operators of these airplanes.
    However, should an affected airplane be imported and placed on the 
U.S. Register in the future, it would take approximately 4 work hours 
per airplane to accomplish the one-time inspection, at an average labor 
rate of $60 per work hour. Based on these figures, the cost impact of 
the proposed inspection requirement on U.S. operators is estimated to 
be $240 per airplane.

Regulatory Impact

    The regulations proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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 copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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 removing amendment 39-11063 (64 FR 
10935, March 8, 1999), and by adding a new airworthiness directive 
(AD), to read as follows:

Boeing: Docket 99-NM-69-AD. Supersedes AD 99-05-15, Amendment 39-
11063.

    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 (c)(1) 
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:

Restatement of Requirements of AD       99-05-15

One-Time Inspection

    (a) Within 90 days after March 23, 1999 (the effective date of 
AD 99-05-15, amendment 39-11063), 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.

Replacement

    (b) Within 12 months after the effective date of this AD, 
replace all existing bolts and attachment nuts at the forward and 
aft end attachment of each elevator tab push rod

[[Page 67810]]

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.

Alternative Methods of Compliance

    (c)(1) 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.
    (2) Alternate methods of compliance, approved previously in 
accordance with AD 99-05-15, amendment 39-11063, are not considered 
to be approved as alternate methods of compliance with this AD.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

Special Flight Permits

    (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.

    Issued in Renton, Washington, on November 29, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-31435 Filed 12-2-99; 8:45 am]
BILLING CODE 4910-13-U