77-14-11 BRITISH AIRCRAFT CORPORATION: Amendment 39-2963. Applies to BAC 1- 11 200 and 400 series airplanes certificated in all categories, and equipped with any of the following flap assemblies:
Inboard Flap Assy.
Center Flap Assy.
Outboard Flap Assy.
AB09 A1/2 or
AB09 A3/4 or
AB09 A5/6 or
AK09 A121/2 or
AK09 A123/4 or
AK09 A125/6 or
AK09 A1579/80 or
AP09 A3/4 or
AP09 A5/6 or
AP09 A1/2 or
EN09 A3/4
EN09 A5/6
AP09 A501/2 or
EN09 A1/2
Compliance is required as indicated.
To detect cracks and prevent possible failure of the flap structure, accomplish the following:
(a) For airplanes equipped with flap assemblies (R/H and L/H) which do not incorporate Modification 57-PM2961, the following inspections apply:
1) Upon accumulating 20,000 landings on the flap assemblies or within 50 landings after the effective date of this AD, whichever occurs later, unless accomplished within the preceding 200 landings for inboard flap assemblies or 950 landings for center and outboard flap assemblies, visually inspect the top surface skin panels of all flaps for cracks, paying particular attention to the rivet attachment areas.
2) Repeat the inspection of paragraph (a)(1) of this AD at intervals from the last inspection not to exceed 250 landings for the inboard flaps and 1000 landings for the center and outboard flaps.
3) If, during an inspection required by paragraph (a)(1) or (a)(2) of this AD, signs of movement or distress are found at a group of rivets, within 500 landings, unless already accomplished within the preceding 500 landings, conduct an X-ray or visual inspection of the flap internal structure in accordance with paragraph 2.1.1 of the section titled "Accomplishment instructions" of BAC Alert Service Bulletin 57-A-PM5381, Issue 2, dated July 5, 1976, (hereinafter referred to as BAC ASB 57-A-PM5381), or an FAA-approved equivalent.
4) Upon accumulating 20,000 landings on the inboard flapsor within 100 landings after the effective date of this AD, whichever occurs later, unless already accomplished within the preceding 3,400 landings, conduct an X-ray inspection of the flap structure in accordance with paragraph 2.1.3 of BAC ASB 57-A-PM5381, or an FAA-approved equivalent.
5) Repeat the X-ray inspection of the flap structure of the inboard flaps required by paragraph (a)(4) of this AD at intervals not to exceed 3,500 landings from the last inspection.
6) If an inspection required by paragraph (a)(4) or (a)(5) of this AD confirms that the internal structure is free of cracks, and if the skin panels are free of cracks, the intervals of 250 landings for the repetitive visual inspection of the skin panels of the inboard flaps required by paragraph (a)(2) of this AD may be increased to 1,200 landings.
7) Upon accumulating 23,000 landings on the center and outboard flaps, or within 500 landings after the effective date of this AD, whichever occurs later, unless already accomplished, conduct an X-ray inspection of the flap structure in accordance with the instructions contained in paragraph 2.1.6 of BAC ASB 57-A-PM5381, or an FAA-approved equivalent.
(b) For airplanes equipped with flap assemblies (R/H and L/H) that incorporate Modifications 57-PM-1931 and 57-PM-2961, the following inspections apply:
1) Upon accumulating 25,000 landings on the flap assemblies or within 1,000 landings after the effective date of this AD, whichever occurs later, unless already accomplished, conduct an X-ray inspection of the flap structure in accordance with paragraph 2.2.1 of BAC ASB 57-A-PM5381, or an FAA-approved equivalent.
2) Repeat the inspection required by paragraph (b)(1) of this AD, for the inboard flaps only, at intervals not to exceed 5,000 landings.
(c) For airplanes equipped with flap assemblies (R/H and L/H) that were originally manufactured to the standard of Modification 57-PM-2961, upon accumulating 25,000 landingson the flap assemblies, or within 1000 landings after the effective date of this AD, whichever occurs later, unless already accomplished, conduct an X-ray inspection of the flap structure in accordance with paragraph 2.3.1 of BAC ASB 57-A-PM5381, or an FAA-approved equivalent.
(d) If one or more cracks are found in the top skin panels during an inspection required by this AD, comply with the following as applicable:
1) If skin panel cracks are found that do not exceed two inches in length (measured from the skin panel edge) and no more than three such cracks exist over the span of any one spar with no more than one crack at any rib station, the flap may continue in service provided that each crack is measured for propagation at intervals not to exceed 250 landings.
2) If more than three skin panel cracks are found over the span of any one spar or more than one crack is found at any rib station, all of which measure less than two inches in length (measured from the skin panel edge), before further flight, accomplish temporary repairs in accordance with Figure 2A or 2B of BAC ASB 57-A-PM5381, or accomplish a repair in accordance with the BAC 1-11 Structural Repair Manual, Chapter 57-02-4, or an FAA-approved equivalent.
3) If a skin panel crack is found that exceeds two inches in length (measured from the skin panel edge), before further flight, accomplish a repair in accordance with the BAC 1-11 Structural Repair Manual, Chapter 57-02-4, or an FAA-approved equivalent.
4) If one or more skin cracks that do not exceed six inches in length are found along a rib flange rivet line, and providing not more than one crack exists at any one rib station and not more than two cracks are found on any one flap surface, before further flight, accomplish a temporary repair of the cracked area in accordance with Figure 3 of BAC ASB 57-A- PM5381, or accomplish a repair in accordance with BAC 1-11 Structural Repair Manual, Chapter 57-02-4, or an FAA-approved equivalent.
5) If a skin crack that exceeds six inches in length is found along a rib flange rivet line or if more than two cracks of any length are found on any one flap surface, before further flight, accomplish a repair of the cracked areas in accordance with the BAC 1-11 Structural Repair Manual, Chapter 57-02-4, or an FAA-approved equivalent.
6) If skin cracks are found emanating from beneath rubbing strips or external patches, before further flight, remove the rubbing strip or external patch and accomplish a repair in accordance with the criteria established in paragraph (d)(4) or (d)(5) of this AD as applicable.
7) If temporary repairs are accomplished for cracked areas in the skin panels in compliance with paragraph (d)(2), (d)(4), or (d)(6) of this AD, within 15 landings after accomplishing the temporary repair, conduct an X-ray inspection of the internal structure of the flap in the area of the repair in accordance with paragraph 2.1.3 of BAC ASB 57-A-PM5381, or an FAA-approved equivalent. If the X-ray inspection confirms that the internal structure is free of cracks, the flap with temporary repairs incorporated may remain in service for a period not to exceed 1,200 landings at which time the temporary repairs must be replaced by repairs in accordance with the BAC 1-11 Structural Repair Manual, Chapter 57-02-4, or an FAA-approved equivalent.
(e) If one or more cracks are found in the flap spars as a result of an inspection required by this AD, the following apply:
1) Except as provided in paragraph (e)(2) of this AD, before further flight, repair the cracked area of the spar in accordance with Figure 4 or Figure 5, or both, as applicable, of BAC ASB 57-A-PM5381, or an FAA-approved equivalent.
2) If one or more cracks are found in the flanges of the flap spars but they have not progressed into the web of the spar, the flap assembly may remain in service for an additional 600 landings provided that, before further flight, a temporary repair of the affected area is accomplished in accordance with Figure 2A or 2B of BAC Alert Service Bulletin 57-A-PM5381, Issue 2, dated July 5, 1976, or an FAA-approved equivalent. Upon accumulating the 600 additional landings, repair the cracked area of the spar in accordance with Figure 4 or Figure 5, or both, as applicable, of BAC ASB 57-A-PM5381, or an FAA-approved equivalent.
(f) For the purpose of complying with this AD, subject to acceptance by the assigned Airworthiness Inspector, the number of landings, if not recorded, may be determined by dividing the actual number of flight hours for the particular flap assembly by the operator's fleet average time from takeoff to landing for the airplane type.
(g) Upon the request of an operator, the Chief, Aircraft Certification Staff, FAA, Europe, Africa and Middle East Region, c/o American Embassy, APO New York, N.Y. 09667, may adjust crack length limitations, approve alternate repetitive inspection intervals and procedures, and approve alternate rework procedures to facilitate continued operations by the operator, if data substantiating such action are submitted by the operator.
(h) The repetitive inspections required by paragraphs (a)(2) and (a)(5) of this AD may be discontinued upon the incorporation of Modifications 57-PM-1931, 57-PM-2961, and 57- PM5381.
(i) The repetitive inspections required by paragraph (b)(2) of this AD may be discontinued upon the incorporation of Modification 57-PM5381.
This amendment becomes effective July 21, 1977.