AD 99-13-51

Effective July 6, 1999, to all persons except those persons to whom it was made immediately effective by telegraphic AD T99-13-51, issued June 10, 1999, which contained the requirements of this amendment.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of July 6, 1999.

Comments for inclusion in the Rules Docket must be received on or before August 30, 1999.

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-133-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

The applicable service information 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.

Gregory L. 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.

On June 10, 1999, the FAA issued telegraphic AD T99-13-51, which is applicable to certain Boeing Model 737-700 and -800 series airplanes.

On June 2, 1999, the FAA received a report of a severe vibration incident on a Boeing Model 737-800 series airplane, which had accumulated 3,517 total flight hours and 1,284 total flight cycles. The airplane was involved in a high-speed descent with speed brakes extended while operating at an airspeed of 320 knots. During the descent, severe vibration occurred at 250 knots. At 230 knots, the speed brakes were retracted and the vibration stopped. The landing was uneventful.

Inspection of the airplane revealed that the upper flange of the right elevator tab mast fitting, to which the elevator tab push rods are attached, was found fractured. The lower flange of the fitting was not damaged. In addition, excessive freeplay in the elevator tab also was observed and measured during the inspection.

Further analysis confirmed that the damage to the fitting was aggravated by speed brake induced airframe vibrations. Such vibration could lead to damage of the elevator tab mast fitting, excessive freeplay in the tab, and consequent separation of the tab mast fitting from the tab. Excessive freeplay in the tab could result in severe airframe vibrations and consequent damage to the tab, elevator, and horizontal stabilizer. Separation of the elevator tab mast fitting will result in a free tab. These conditions, if not corrected, could result in reduced controllability of the airplane.

The FAA has reviewed and approved Boeing Alert Service Bulletin 737-55A1068, dated June 9, 1999, which describes procedures for repetitive high frequency eddy current (HFEC) inspections of the tab mast fitting of the left and right elevator tab assembly to detect cracking, and a one-time elevator tab freeplay check to detect excessive freeplay of the elevator tab; and corrective actions, if necessary. The alert service bulletin also describes procedures for installing an additional high-strength fastener on the tab mast fitting (time-limited modification).

In addition, the alert service bulletin references removing and replacing the cracked tab mast fitting with a new, improved fitting. Such replacement, if accomplished, eliminates the need for the repetitive inspections.

Since the unsafe condition described is likely to exist or develop on other airplanes of the same type design, this airworthiness directive is issued to require revising the Limitations Section of the FAA-approved Airplane Flight Manual (AFM) to prohibit operation of the airplane at certain airspeeds with the speed brakes extended, and at certain altitudes.

This AD also requires repetitive HFEC inspections of the tab mast fitting of the left and right elevator tab assembly to detect cracking, and a one-time elevator tab freeplay check to detect excessive freeplay of the elevator tab; and corrective actions, if necessary. This AD also provides for optional terminating action for the repetitive HFEC inspections.

Certain actions are required to be accomplished in accordance with the alert service bulletin described previously.

Additionally, this AD requires installing an additional high-strength fastener on the tab mast fitting (time-limited modification). Such installation terminates the AFM revision and allows extension of the repetitive interval for accomplishment of the HFEC inspections.

It should be noted that, although this AD prohibits the deployment of the spoilers at speeds in excess of 310 knots indicated airspeed (IAS), the FAA recognizes that under emergency circumstances, previous pilot training and human factors could result in deployment of the spoilers at such speeds notwithstanding the AFM prohibition. In this event, this AD requires accomplishment of the HFEC inspection of the tab mast fitting and of the check of the tab for freeplay prior to further flight after landing.

Since it was found that immediate corrective action was required, notice and opportunity for prior public comment thereon were impracticable and contrary to the public interest, and good cause existed to make the AD effective immediately by individual telegrams issued on June 10, 1999, to all known U.S. owners and operators of Boeing Model 737-700 and -800 series airplanes. These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to section 39.13 of the Federal Aviation Regulations (14 CFR 39.13) to make it effective to all persons.

In the preamble to AD T99-13-51, the FAA indicated that the actions required by that AD were considered to be interim action and that the FAA may consider further rulemaking to require replacement of the tab mast fitting with a new, improved fitting.

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.

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-133-AD.'' The postcard will be date stamped and returned to the commenter.

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.

Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

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:

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.