Airworthiness Directive · Amendment 39-11744 · Lockheed Model L-1011-385 Series Airplanes
Lockheed Model L-1011-385 Series Airplanes
All Model L-1011-385 series airplanes, as listed in Lockheed Service Bulletin 093-53-279, dated May 6, 1998; certificated in any category.
Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (f) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
This amendment adopts a new airworthiness directive (AD), applicable to all Lockheed Model L-1011-385 series airplanes, that requires repetitive inspections to detect cracking of the fuselage skin in the areas of the left- and right-hand stringerless sidewall window belts, and repair, if necessary. This amendment is prompted by reports of fatigue cracks found in the fuselage skin where the skin thickness steps from 0.40 to 0.23 inch. The actions specified by this AD are intended to detect and correct cracking of the fuselage skin, which could result in reduced structural integrity of the airplane.
To detect and correct cracking of the fuselage skin, which could result in reduced structural integrity of the airplane, accomplish the following:
(a) Perform an ultrasonic inspection on the fuselage skin in the area of the stringerless sidewall window belts, at the radii on both the forward and aft sides of the machined cutout where the fuselage skin steps from 0.40 to 0.23 inch, to detect cracking in the base of the radii. Accomplish the inspection in accordance with Lockheed Service Bulletin 093-53-279, dated May 6, 1998, at each of the 6 specific inspection zones identified in the service bulletin at the later of the times specified in paragraphs (a)(1) and (a)(2) of this AD.
(1) Prior to the accumulation of 20,000 total flight cycles; or
(2) Within 600 flight cycles or 6 months after the effective date of this AD, whichever occurs first.
(b) For readings of less than 20 percent obtained at all 6 inspection zones during the ultrasonic inspection required by paragraph (a) of this AD: Repeat the ultrasonic inspection thereafter at intervals not to exceed 1,500 flight cycles.
(c) Except as provided by paragraph (e) of this AD: For any reading of 20 percent or greater and less than or equal to 50 percent obtained at any inspection zone during the ultrasonic inspection required by paragraph (a) of this AD, prior to further flight, perform a low frequency eddy current (LFEC) inspection to measure the depth of the cracking, in accordance with Lockheed Service Bulletin 093-53-279, dated May 6, 1998.
(1) If the results of the LFEC inspection are outside the reject zone, as defined in the service bulletin: Within 1,500 flight cycles, repeat both the ultrasonic and LFEC inspections specified by paragraphs (a) and (c), respectively, of this AD.
(i) If the results of the LFEC inspection specified by paragraph (c)(1) of this AD are outside the reject zone: Within 1,800 flight cycles after the initial crack finding, as detected during the ultrasonic inspection specified in paragraph (a) of this AD, repair any affected inspection zone in accordance with Part II of the Accomplishment Instructions of the service bulletin. Such repair constitutes terminating action for the repetitive inspection requirements of this AD for the repaired inspection zone only.
(ii) If the results of the LFEC inspection specified by paragraph (c)(1) of this AD are within the reject zone: Prior to further flight, repair any affected inspection zone in accordance with Part II of the Accomplishment Instructions of the service bulletin. Such repair constitutes terminating action for the repetitive inspection requirements of this AD for the repaired inspection zone only.
(2) If the results of the LFEC inspection are within the reject zone, as defined in the service bulletin: Prior to further flight, repair any affected inspection zone in accordance with Part II of the Accomplishment Instructions of the service bulletin. Such repair constitutes terminating action for the repetitive inspection requirements of this AD for the repaired inspection zone only.
(d) Except as provided by paragraph (e) of this AD: For any reading of 50 percent or greater obtained at any inspection zone during the ultrasonic inspection required by paragraph (a) of this AD, prior to further flight, perform a LFEC inspection to measure the depth of the cracking, in accordance with Lockheed Service Bulletin 093-53-279, dated May 6, 1998.
(1) If the results of the LFEC inspection are outside the reject zone, as defined in the service bulletin: Within 300 flight cycles, repeat both the ultrasonic and LFEC inspections specified in paragraphs (a) and (c), respectively, of this AD.
(i) If the results of the LFEC inspection specified by paragraph (d)(1) of this AD are outside the reject zone: Within 600 flight cycles after the initial crack finding, as detected during the ultrasonic inspection specified in paragraph (a) of this AD, repair any affected inspection zone in accordance with Part II of the Accomplishment Instructions of the service bulletin. Such repair constitutes terminating action for the repetitive inspection requirements of this AD for the repaired inspection zone only.
(ii) If the results of the LFEC inspection specified by paragraph (d)(1) of this AD are within the reject zone: Prior to further flight, repair any affected inspection zone in accordance with Part II of the Accomplishment Instructions of the service bulletin. Such repair constitutes terminating action for the repetitive inspection requirements of this AD for the repaired inspection zone only.
(2) If the results from the LFEC inspection are within the reject zone, as defined in the service bulletin: Prior to further flight, repair any affected inspection zone in accordance with Part II of the Accomplishment Instructions of the service bulletin. Such repair constitutes terminating action for the repetitive inspection requirements of this AD for the repaired inspection zone only.
(e) For any inspection results that require repair in two adjacent zones: Prior to further flight, repair in accordance with a method approved by the Manager, Atlanta Aircraft Certification Office (ACO), FAA, Small Airplane Directorate.
