AD 96-26-52

Effective January 8, 1997, to all persons except those persons to whom it was made immediately effective by telegraphic AD T96-26-52, issued December 20, 1996, which contained the requirements of this amendment.

Comments for inclusion in the Rules Docket must be received on or before March 4, 1997.

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 96-NM-280-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Service information pertaining to this rulemaking action 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.

Tamara L. Dow, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, 1601 Lind Avenue, SW., Renton, Washington 98055-4056, telephone (206) 227-2771; fax (206) 227-1181.

On December 20, 1996, the FAA issued telegraphic AD T96-26-52, which is applicable to certain Boeing Model 747 series airplanes.

That action was prompted by a report indicating that a fuse pin had migrated \5/8\ inch out of an inboard spring beam fitting on the Number 1 engine pylon of a Boeing Model 747-400 series airplane. In addition, the mating nut to this pin had backed off approximately \3/10\ inch from full engagement with the pin. The discrepant fuse pin was detected after maintenance personnel observed that the access door (part number 65B94112-43) to this fuse pin protruded outward from its adjacent pylon structure.

At the time this discrepancy was found, the airplane had accumulated 12,446 total hours time-in-service, and accomplished 1,439 total landings. Prior to delivery of this airplane in June 1994, the manufacturer had installed fuse pins in the spring beam fitting that are made of 15-5 corrosion resistant steel (``third generation pins''). These pins replaced existing pins made of 4330 or 4340 steel.

Migration of the fuse pin, if not detected and corrected in a timely manner, could result in failure of the engine pylon and consequent separation of the engine from the wing.

The FAA previously had issued AD 95-13-05 [amendment 39-9285 (60 FR 33333, dated June 28, 1995; as corrected at 60 FR 35452, July 7, 1995)], which applies to certain Boeing Model 747 series airplanes equipped with Rolls Royce Model RB211 series engines. The FAA also had issued AD 95-13-06 [amendment 39-9286 (60 FR 33338, June 28, 1995; as corrected at 60 FR 37500, July 20, 1995)], which applies to certain Model 747 series airplanes equipped with General Electric Model CF6-80C2 series engines or Pratt & Whitney Model PW4000 series engines. These AD's, which are almost identical, require modification of the nacelle strut and wing structure of the applicable airplanes. Among the actions required by both AD's is the installation of a mechanical secondary retention to prevent the fuse pins for the midspar/spring beam fittings from migrating.

At the time the discrepancy described above was discovered, the nacelle strut and wing modification had not yet been accomplished on the incident airplane;

consequently, the secondary retention device had not yet been installed either. (The secondary retention device has been installed during production of airplanes beginning at line number 1047.)

Since the unsafe condition described is likely to exist or develop on other airplanes of the same type design, the FAA issued Telegraphic AD T96-26-52 to prevent migration of this fuse pin, subsequent failure of the engine pylon, and consequent separation of the engine from the wing. The AD requires repetitive detailed visual inspections of the access doors to the midspar/spring beam fuse pins on all engine pylons to detect cracks on the external surface, and repair, if necessary. In addition, the AD requires repetitive detailed visual inspections of each midspar/spring beam fuse pin to detect if it protrudes beyond its mating nut by a specified distance, and repair, if necessary. These inspections are to be repeated until the terminating modifications currently required by AD 95-13-05 or AD 95-13-06, as applicable, are accomplished.

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 December 20, 1996, to all known U.S. owners and operators of Boeing Model 747 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.

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 96-NM-280-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, 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.