03-13647. Airworthiness Directives; Boeing Model 777 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Proposed rule; withdrawal.

SUMMARY:

This action withdraws a notice of proposed rulemaking (NPRM) that proposed a new airworthiness directive (AD), applicable to all Boeing Model 777 series airplanes. That action would have required repetitive inspections for cracking of the floor beam structure located at body station 246; and repair, if necessary. Since the issuance of the NPRM, the Federal Aviation Administration (FAA) has received new data that indicate that the unsafe condition does not exist on the airplanes identified in the proposed rule. Accordingly, the proposed rule is withdrawn.

FOR FURTHER INFORMATION CONTACT:

Gary Oltman, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to add a new airworthiness directive (AD), applicable to all Boeing Model 777 series airplanes, was published in the Federal Register as a Notice of Proposed Rulemaking (NPRM) on June 19, 2002 (67 FR 41640). The NPRM would have required repetitive inspections for cracking of the floor beam structure located at body station 246; and repair, if necessary. That action was prompted by numerous reports of fatigue cracking of the floor beam structure located at body station (BS) 246 on several Boeing Model 777 series airplanes. The proposed actions were intended to find and fix such cracking, which could extend and sever the floor beam, resulting in rapid depressurization of the airplane and consequent collapse of the floor structure.

Actions That Occurred Since the NPRM Was Issued

Since the issuance of that NPRM, the FAA has received new information as a comment from the airplane manufacturer (Boeing). The manufacturer indicated that even though the BS 246 floor beam cracking is not desirable, it did not result in an unsafe condition. As a result, we met with the manufacturer on December 5, 2002, and the manufacturer presented additional supporting data and analysis results.

We have reviewed the data and concur with the manufacturer's conclusion that operators continue to find cracks, and that the type and extent of the floor beam cracking remains unchanged since the original findings. The analysis also showed that the cracked beam is prevented from deflecting to the point of affecting critical flight control.

Based on these facts, we agree with the manufacturer's assessment that the cracking will not result in an unsafe condition, and the critical structural elements in the floor beam will continue to retain the required structural integrity throughout the life of the airplane.

FAA's Conclusions

Upon further consideration, the FAA has determined that the unsafe condition does not exist on the airplanes identified in the NPRM. Accordingly, the proposed rule is hereby withdrawn.

Withdrawal of this NPRM constitutes only such action, and does not preclude the agency from issuing another action in the future, nor does it commit the agency to any course of action in the future.

Regulatory Impact

Since this action only withdraws a notice of proposed rulemaking, it is neither a proposed nor a final rule and therefore is not covered under Executive Order 12866, the Regulatory Flexibility Act, or DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979).

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Withdrawal

Accordingly, the notice of proposed rulemaking, Docket 2001-NM-30-AD, published in the Federal Register on June 19, 2002 (67 FR 41640), is withdrawn.

Issued in Renton, Washington, on May 27, 2003.

Vi L. Lipski,

Manager, Transport Airplane Directorate, Aircraft Certification Service.