AD 75-11-09 ACTIVE

75-11-09 LOCKHEED-CALIFORNIA COMPANY: Amendment 39-2219. Applies to Model L-1011-385-1 Series Airplanes, certificated in all categories, incorporating Lockheed counterbalances, P/N 671827-107, -109, -113.

To prevent possible failure of Belleville springs resulting in inoperative counterbalances of the Type I. emergency door actuation system, which could cause the most rearward Type I. left and right doors to be inoperative in the emergency mode, accomplish the following:

Compliance required as indicated.

(a) For airplanes incorporating P/N 671827-113 counterbalances:

(1) Within 300 additional flight hours after the effective date of this AD, unless already accomplished, reduce the spring prewind per accomplishment instructions of Lockheed-California Company Service Bulletin 093-52-072, Revision Number 1, dated May 8, 1975, or later FAA-approved revisions.

(2) Within 300 additional flight hours after the effective date of this AD, unless previously accomplishedwithin the last l,300 flight hours prior to the effective date of this AD, and at intervals not to exceed 1,600 hours thereafter, until (3), below is accomplished, perform the operational checks on the door emergency mode for proper functioning of the counterbalance for the most rearward Type I. left and right doors, per the accomplishment instructions of Lockheed-California Service Bulletin 093-52-072, Revision Number 1, dated May 8, 1975, or later FAA-approved revisions.

(i) If the operational checks are not satisfactory, replace the defective counterbalances, P/N 671827-113, with either a P/N 671827-107, or -109 counterbalance per Lockheed-California Company Service Bulletin 093-52-072, Revision Number 1, dated May 8, 1975, or later FAA-approved revisions, or a counterbalance P/N 671827-115 or -117 per Lockheed-California Service Bulletin 093-52-076, Revision Number 1, dated May 8, 1975, or later FAA-approved revisions. Prior to further flight perform the operational checks toensure that the operation of the doors with the new counterbalances is satisfactory.

(ii) Mark the defective P/N 671827-113 counterbalances in a conspicuous manner to prevent inadvertent return to service.

(3) Within 8000 hours additional flight time after the effective date of this AD, unless already accomplished, replace all counterbalances P/N 671827-113 with either counterbalances P/N 671827-115 or -117, per Service Bulletin 093-52-076, Revision Number 1, dated May 8, 1975, or later FAA-approved revisions or with counterbalances P/N 671827-107 or - 109 per Lockheed-California Company Service Bulletin 093-52-072, Revision Number 1, dated May 8, 1975, or later FAA-approved revisions. Prior to further flight perform the operational checks to ensure that the operation of the doors with the new counterbalances is satisfactory. If satisfactory operation of the doors exist no further inspections are required per this AD.

(b) For airplanes incorporating counterbalances P/N671827-107 and -109:

(1) Within 300 additional flight hours after the effective date of this AD, unless already accomplished, perform the operational checks of the door emergency mode for the most rearward Type I. left and right doors, per the accomplishment instructions of the Lockheed- California Company Service Bulletin 093-52-072, Revision Number 1, dated May 8, 1975, or later FAA-approved revisions.

(i) If the operational checks are satisfactory then no further checks are required per this AD.

(ii) If the operational checks are not satisfactory, replace the defective counterbalances, P/N 671827-107 or -109, with either a new counterbalance, P/N 671827-107 or - 109, per Lockheed-California Company Service Bulletin 093-52-072, Revision Number 1, dated May 8, 1975 or later FAA-approved revisions, or with counterbalances, P/N 671827-115 or -117, per Lockheed-California Company Service Bulletin 093-52-076, Revision Number 1, dated May 8, 1975 or later FAA-approved revisions. Perform the doors operational checks to ensure that the operation of the doors with the new counterbalance is satisfactory. If satisfactory operation of the doors exist no further inspections are required per this AD.

(iii) Mark the defective P/N 671827-107 or -109 counterbalances in a conspicuous manner to prevent inadvertent return to service.

(c) Equivalent inspections may be approved by the Chief, Aircraft Engineering Division, FAA Western Region.

(d) Airplanes may be flown to a base where the inspections and modifications can be performed per FAR's 21.197 and 21.199.

This amendment becomes effective May 30, 1975.