01-25185. Airworthiness Directives; Lockheed Model L-1011-385 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 certain Lockheed Model L-1011-385 series airplanes. That action would have required the replacement of the flap position indicator with an improved flap position indicator. Since the issuance of the NPRM, the Federal Aviation Administration (FAA) has received new data that indicate that currently there are adequate annunciation provisions and crew procedures to safely detect and accommodate slat drive failures. Accordingly, the proposed rule is withdrawn.

FOR FURTHER INFORMATION CONTACT:

Hector Hernandez, Aerospace Engineer, Systems and Flight Test Branch, ACE-116A, FAA, Atlanta Aircraft Certification Office, One Crown Center, 1895 Phoenix Boulevard, suite 450, Atlanta, Georgia 30349; 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 certain Lockheed Model L-1011-385 series airplanes, was published in the Federal Register as a Notice of Proposed Rulemaking (NPRM) on June 17, 1998 (63 FR 33019). The proposed rule would have required the replacement of the flap position indicator with an improved flap position indicator. That action was prompted by a report indicating that an airplane landed at an excessive sink rate and sustained substantial structural damage when the leading edge slats failed to extend for landing and the flightcrew failed to increase airspeed in response, due to inadequate annunciation of the slat failure. The proposed actions were intended to prevent such inadequate annunciation, which could result in the flightcrew being unaware when the leading edge slats fail to extend properly; such failure could result in reduced stall margins, and consequent reduced controllability of the airplane.

Actions That Occurred Since the NPRM Was Issued

Since the issuance of that NPRM, the FAA has received numerous comments from operators claiming that there are adequate annunciation provisions and crew procedures currently in place. The manufacturer and operators have identified three separate locations that show the position of the slats on Model L-1011 series airplanes:

1. A slat monitor panel at the flight engineer's station displays the position of each of the fourteen individual slat panels by illuminating when each slat reaches the fully extended position, as determined by proximity sensors in each slat's drive mechanism. This slat monitor panel also displays the angular position of both the right and left slat drive trains on a dial-type indicator.

2. A green “LE EXT” annunciation on the flap/slat position indicator on the center instrument panel illuminates when the slats reach the fully extended, 30-degree deflection.

3. Two slat drive fault indicators indicate that the slat drive has been inhibited.

Most but not all slat drive failure modes are detected and actively annunciated by the slat drive fault indicators. Any failure that inhibits the slat travel prior to full extension is clearly indicated on the slat monitor panel and flap/slat position indicator by the “no indication of slat extension” indicator. Current crew procedures call for the flight engineer to check and confirm slat extension prior to landing. To require the production and installation of approximately 180 shipsets of modified indicators (to accommodate the worldwide fleet), which have not been manufactured in more than 15 years, does not is not necessary in light of the additional indications already in place. While the modified indicators do improve slat drive position awareness by actively annunciating the lack of slat extension, currently there are adequate annunciation provisions and crew procedures to safely detect and accommodate slat drive failures.

FAA's Conclusions

Upon further consideration, the FAA has determined that mandating the installation of modified indicators is not necessary or justifiable because current annunciation provisions and crew procedures are adequate to address the identified unsafe condition. 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 98-NM-36-AD, published in the Federal Register on June 17, 1998 (63 FR 33019), is withdrawn.

Issued in Renton, Washington, on October 2, 2001.

Vi L. Lipski,

Manager, Transport Airplane Directorate, Aircraft Certification Service.