Airworthiness directives: Boeing,

[Federal Register: December 3, 1999 (Volume 64, Number 232)]

[Proposed Rules]

[Page 67807-67810]

From the Federal Register Online via GPO Access [wais.access.gpo.gov]

[DOCID:fr03de99-34]

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).

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 filedin 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

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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

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   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. 99-31435Filed12-2-99; 8:45 am]

   BILLING CODE 4910-13-U