AD 81-08-01 R1 ACTIVE

81-08-01 R1 LOCKHEED - CALIFORNIA: Amendment 39-4079 as amended by Amendment 39-4230. Applies to Lockheed Model L-1011-385 series airplanes certificated in all categories.

Compliance required as indicated, unless already accomplished.

To prevent possible loss of ground directional control resulting from unannunciated anti- skid systems failure or excessive pedal force due to parking brake circuit/supply valve failure, accomplish the following:

(a) Commencing ten days from the effective date of this AD, prior to each flight, when "C" hydraulic system (ALT SYS "C") is used for anti-skid wheel braking, perform either a brake system check in accordance with item (1) below or an inspection in accordance with item (2) below:

1. Operations check:

(i) Chock wheels and release parking brake.

(ii) Pressurize both system B and C brake accumulators using AC motor pumps, then turn off pumps.

NOTE: Hydraulic system B and C should not be pressurized while performing this check.

(iii) Select alternate system C with brake system select switch on pilot's center instrument panel.

(iv) Pump brake pedals. B system brake pressure, as indicated on pilot's center instrument panel gauge, should remain steady, and C system brake pressure should decay as pedals are pumped. If B system pressure decays, the NORM system B brake supply valve has failed and must be repaired prior to further flight.

If unable to perform operations check, or if results are inconclusive or suspect, perform visual inspection as specified in item (2):

2. Visual inspection:

(i) Pressurize both B and C hydraulic systems.

(ii) Select ALT SYS C with brake system select switch on pilot's center instrument panel.

(iii) Chock wheels and release parking brake.

(iv) Gain access to both brake supply valve modules (Lockheed P/N 672173-119 (contacts normally open) and Lockheed P/N 672173-121 (contacts normally closed)) in hydraulic service center, located above B and C system accumulators in left and right forward corners of service center.

(v) Verify that two each indicator pins (located adjacent to electrical connector on each valve) are protruding from both B and C brake supply valves. If both pins are not protruding, the valves have failed and must be repaired prior to further flight.

(b) Within 1 year from the effective date of this amendment, modify the parking brake and anti-skid electrical circuits either in accordance with the Accomplishment Instructions of Part 2 of Lockheed Service Bulletin 093-32-145 dated May 1, 1980, or Part 2 of Lockheed Service Bulletin 093-32-179, Revision 1, dated April 7, 1981, or later revisions to either service bulletin approved by the Chief, Los Angeles Area Aircraft Certification Office, FAA Northwest Region.

(c) The pre-flight check/inspections required by paragraph (a) of this AD are no longer required after accomplishment of paragraph (b) of this AD.(d) Alternative means of compliance or other actions which provide an equivalent level of safety may be used when approved by the Chief, Los Angeles Area Aircraft Certification Office, FAA Northwest Region.

(e) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base for the accomplishment of inspections and/or modifications required by this AD.

The manufacturer's specifications and procedures identified and described in this directive are incorporated herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). All persons affected by this directive who have not already received these documents from the manufacturer may obtain copies upon request to Lockheed-California Company, P.O. Box 551, Burbank, California 91520, Attention: Commercial Support Contracts, Dept. 63-11, U-33, B-1.

These documents also may be examined at FAA Northwest Region, 9010 East Marginal Way South, Seattle, Washington 98108, or Los Angeles Area Aircraft Certification Office, 4344 Donald Douglas Drive, Long Beach, California 90808.

Amendment 39-4079 became effective April 16, 1981.

This amendment 39-4230 becomes effective October 18, 1981.