AD 70-02-04

70-02-04 BRITISH AIRCRAFT CORPORATION: Amdt. 39-916. Applies to Viscount Models 744, 745D, and 810 series airplanes.

To provide immediate indication of failures in the electrical generation system, to preclude a simultaneous failure of all generators, and to ensure that emergency electrical power is supplied to certain emergency equipment necessary to continue flight to a safe landing, accomplish the following:

(a) For Models 744, 745D, 810 series airplanes, within the next 1000 hours' time in service after the effective date of this AD, unless already accomplished, install a bus-bar under the voltage warning light in accordance with British Aircraft Corporation Modification Leaflet No. D3232, dated 1 August 1969, (for Model 744 and 745D series airplanes) or No. FG2107, dated 18 July 1969, (for Model 810 series airplanes) or later ARB-approved issues or an FAA-approved equivalent.

(b) For Models 744 and 745D series airplanes, within the next 1000 hours' time in serviceafter the effective date of this AD, unless already accomplished -

(1) Install PVC sheathing over the generator equalizing lines in accordance with British Aircraft Corporation Bulletin for Modification No. D969, Issue 3, dated 17 March 1969, or a later ARB-approved issue or an FAA-approved equivalent; and

(2) Modify the electrical power distribution system in accordance with British Aircraft Corporation Modification Leaflet No. D3239, dated 6 June 1969, or a later ARB-approved issue or an FAA- approved equivalent to ensure that the electrical power for the following equipment is supplied from the No. 4 D.C. Emergency Bus-Bar:

(i) Pitot head heater No. 1 (port).

(ii) Flight deck lighting (i.e., instrument panels, pedestals, magnetic compass and circuit breaker panels).

(iii) D.C. and/or A.C. communication equipment for emergency communications.

(iv) Artificial horizon.

This amendment becomes effective February 5, 1970.