AD/DHC-8/41 - Stall Warning System Computer (Cth)

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES

Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes

AD/DHC-8/41 Stall Warning System Computer 7/95

DM

Applicability: Model DHC-8, series 102, 103 and 106, serial numbers 003 and subsequent with Safe Flight stall warning computers part number (P/N) 3605-4, -5 or -6 installed.

Requirement: 1. Action in accordance with Bombardier Regional Aircraft Division de Havilland Dash 8 Alert Service Bulletin A8-27-73 dated 25 November 1993.

2. Amend the DHC-8 Minimum Equipment List (MEL) in accordance with Temporary Revision No. 20 of the DHC-8 Master Minimum Equipment List (MMEL), ATA Chapter 27, 'FLIGHT CONTROLS', Item 27-2, 'Stall Warning System' for Series 100 pre-mod 8/2072 aircraft only, as follows:

One stall warning computer may be inoperative for three flight days (Category A), provided the inoperative system is deactivated and the remaining operative system is confirmed operative in the 'AIRBORNE MODE' each flight day.

Note: Transport Canada Aviation AD CF-95-06 dated 10 April 1995 refers.

Compliance: 1. Within 50 hours time in service after 18 May 1995, unless already accomplished within the last 400 hours time in service. Thereafter at intervals not to exceed 450 hours time in service.

2. At initial inspection in accordance with this Directive.

Incorporation of de Havilland Modification 8/2072 terminates the requirement for the repetitive test and the amendment to the MEL.

Background: A routine "C" check discovered that the stick shakers did not activate when tested. Investigations have determined that relay contacts within the stall warning computer had become contaminated and no longer provided a sufficient path to ground for shaker operation.