58-10-06 VICKERS: Applies to All Viscount 700 Series Aircraft.
Compliance required as soon as possible but not later than July 31, 1958.
A case has occurred during production on the Viscount 700 Series aircraft, of the fracturing of the cranked operating lever (P/N N.69195) of the flap selector switch, Type D.7406. Investigation has established that the fracture is the result of excessive case-hardening of the mild steel lever (P/N N.69195) such that the lever became brittle. The hardened mild steel lever (P/N N.69195) must be replaced by a mild steel lever (P/N N.69195/1) which is identified by a blue spot on the outside face of the lever crank which is visible when positioned in the throttle pedestal.
Vickers-Armstrong Aircraft Ltd. PTL No. 188 and Modification Bulletin No. D.2673 cover the same subject. This modification is considered mandatory by the British Air Registration Board. The FAA concurs and considers compliance mandatory.