71-01-02 BRITISH AIRCRAFT CORPORATION: Amdt. 39-1133. Applies to Viscount Models 744, 745D, and 810 series airplanes.
Compliance is required as indicated.
To prevent failure of the flap gearbox drive motor assembly due to break-up of the steel inner clutch plate, accomplish the following:
(a) Within the next 25 landings after the effective date of this AD, or within the next 700 landings after the clutch plate was replaced in accordance with AD 68-23-07, whichever occurs later, unless already accomplished, accomplish the following:
(1) Replace the flap gearbox drive motor clutch assembly with a solid spline adaptor by incorporating Rotax Modification No. 4603c Part A in accordance with Rotax Service Bulletin 24-337, Revision 2, dated November 24, 1969, or later ARB-approved issue or an FAA- approved equivalent.
(2) Replace obsolete clutch driving shafts, clutch shafts, and brake drum assemblies of the flap gearbox drive motor assembly having obsolete part numbers, with serviceable replacement components having replacement part numbers, in accordance with the following table:
Component
Obsolete Part
Numbers
Replacement
Part Numbers
Clutch driving
shaft
N117500 and
N145421
N149327,
N187295,
or N196101
Clutch shaft
Brake drum
assembly
N98825
N117504 and
N117504/1
N149328
N149329
(3) Replace clutch driving shafts P/Ns N149327 or N187295, having a total of 5,000 or more landings on the shaft with a serviceable shaft, P/N 149327, N187295, or N196101.
(b) Replace clutch driving shafts P/Ns N149327 and N187295 at intervals not to exceed 5,000 landings on the shaft, and replace clutch driving shafts P/N N196101 at intervals not to exceed 10,000 landings on the shaft.
(c) Within the next 500 landings after the effective date of this AD, unless already accomplished within the last 4,500 landings, and thereafter at intervals not to exceed 5,000 landings since the last inspection, visually inspect the brake drum assembly P/N 149329 for cracks in accordance with Rotax Service Bulletin No. 24-142 dated February 11, 1966, or later ARB-approved issue or an FAA-approved equivalent, and replace drums found to be cracked with serviceable drums of the same part number.
(d) Upon completion of the replacements required by paragraph (a), remove the placard and the temporary in flight procedures in the Airplane Flight Manual required by AD 68- 23-07.
(e) For the purpose of complying with this AD, subject to acceptance by the assigned maintenance inspector the number of landings may be determined by dividing each airplane's hours' time in service by the operator's fleet average time from take-off to landing for the BAC Viscount airplane.
(British Aircraft Corporation Preliminary Technical Leaflets No. 148 and No. 283 cover this same subject.)
This supersedes Amendment 39-263 (31 F.R. 10022), AD 66-19-05, and Amendment 39- 695 (33 F.R. 16493), AD 68-23-07.
Thisamendment becomes effective January 21, 1971.