75-26-12 BRITISH AIRCRAFT CORPORATION: Amendment 39-2468. Applies to British Aircraft Corp. (BAC) Viscount Model 700 and 810 series airplanes.
Compliance is required as indicated, unless already accomplished.
To prevent possible fatigue failure of the No. 1 and 2 landing flap torque shaft assemblies, accomplish the following:
(a) For No. 1 torque shaft assemblies (LH and RH), comply with the following:
(1) Torque tubes fitted to torque shaft assemblies for which total landings can be determined and which have accumulated in excess of 26,000 landings but not more than 28,000 landings on the effective date of this AD may remain in service for 2,000 additional landings with no special inspections after which time they must be replaced with new torque tubes of the same part number in accordance with paragraph (a)(5) of this AD.
(2) Torque tubes fitted to torque shaft assemblies for which the total landings can be determined and which have accumulated in excess of 28,000 landings on the effective date of this AD may be continued in service, subject to the inspection requirements of paragraph (a)(4) of this AD, for 2,000 additional landings after which they must be replaced with new torque tubes of the same part number in accordance with paragraph (a)(5) of this AD.
(3) Torque tubes fitted to torque shaft assemblies for which total landings cannot be determined must use in lieu thereof the total landings on the aircraft on which they are installed and comply with either paragraph (a)(1) or (a)(2) of this AD as applicable.
NOTE: If total landings on the aircraft are not known, an operator may substitute a value for total landings established by dividing the total aircraft hours by the average flight length for the particular aircraft, subject to the approval of the assigned FAA Inspector.
(4) Torque tubes fitted to torque shaft assemblies may remain in service for 2,000 additional landings in accordance with paragraph (a)(2) of this AD, subject to the following conditions:
(i) Within 50 landings after the effective date of this AD and thereafter at intervals not to exceed 50 landings until replaced in accordance with paragraph (a)(2) of this AD, inspect the torque tubes in accordance with 2.2.1 of Alert PTL No. 290 (700 series) or Alert PTL No. 158 (810 series), both dated August 23, 1972, or an FAA-approved equivalent. If any cracks are found in the torque tubes as a result of this inspection, before further flight, replace the torque tubes with new parts of the same part numbers in accordance with paragraph (a)(5) of this AD.
(ii) Within 500 landings from the effective date of this AD and thereafter at intervals not to exceed 500 landings until replaced in accordance with paragraph (a)(2) of this AD, remove the torque shaft assemblies and inspect and rework in accordance with paragraph 2.2.2 of Alert PTL No. 290 (700 series) or Alert PTL No. 158 (810 series), both dated August 23, 1972, or an FAA-approved equivalent. Where an inspection required by this paragraph coincides with an inspection interval specified in paragraph (a)(4)(1) of this AD, the inspection conducted in accordance with this paragraph is considered as showing compliance with the inspection required by paragraph (a)(4)(i) of this AD. If any cracks are found in the torque tubes or end fittings as a result of this inspection, replace cracked parts with new parts of the same part numbers in accordance with the assembly instructions specified in paragraph (a)(5) of this AD.
(5) Torque tubes replaced in accordance with any provisions of this AD must be assembled to the torque shaft assembly in accordance with figure 2 of Alert PTL No. 290 (700 series) or PTL No. 158 (810 series), both dated August 23, 1972, or an equivalent approved by the Chief, Aircraft Certification Staff, FAA, c/o American Embassy, APO New York 09667.
6) Replacement torque tubes installed in accordance with the provisions of this AD must be replaced within 20,000 landings from new. Thereafter inspect replacement torque tubes in accordance with paragraph 2.3 of Alert PTL No. 290 (700 series) or Alert PTL No. 158 (810 series), both dated August 23, 1972, or an FAA-approved equivalent.
(b) For No. 2 torque shaft assemblies (LH and RH), comply with the following:
(1) For torque tubes fitted to torque shaft assemblies, for which total landings can be determined, within 500 landings after the effective date of this AD or before accumulating 28,500 landings, whichever occurs later, and thereafter at intervals not to exceed 500 landings, inspect the torque tubes in accordance with paragraph 2.4.1 of Alert PTL No. 290 (700 series) or Alert PTL No. 158 (810 series), both dated August 23, 1972, or an FAA-approved equivalent.
(2) Within 1,500 landings after the initial inspection required by paragraph (b)(1) of this AD, and thereafter at intervals not to exceed 2,000 landings from the last inspection, remove the torque shaft assemblies and inspect the torque tubes and end fittings for cracks in accordance with paragraph 2.4.2 of Alert PTL No. 290 (700 series) or Alert PTL No. 158 (810 series), both dated August 23, 1972, or an FAA-approved equivalent. Where an inspection required by this paragraph coincides with an inspection interval specified in paragraph (b)(1) of this AD, the inspection conducted in accordance with this paragraph is considered as showing compliance with that required by paragraph (b)(1) of this AD.
(3) If cracks are found as a result of the inspections conducted in accordance with paragraphs (b)(1) or (b)(2) of this AD, before further flight, replace the cracked parts with new parts of the same part number. Where new torque tubes are installed as a result of the inspections specified in paragraphs (b)(1) and (b)(2) of this AD, the repetitive inspections required by paragraphs (b)(1) and (b)(2) must be initiated upon accumulating 28,000 landings on the new torque tubes.
(4) Torque tubes fitted to torque shaft assemblies for which the total landings cannot be determined, must use in lieu thereof the total landings of the aircraft on which they are installed for the purpose of complying with paragraph (b)(1) of this AD.
NOTE: If total landings of the aircraft are not known, an operator may substitute a value for total landings established by dividing the total aircraft hours by the average flight length for the particular aircraft, subject to the approval of the assigned FAA Inspector.
This amendment becomes effective on January 14, 1976.