AIRWORTHINESS DIRECTIVE
For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.
Bombardier (Boeing Canada/de Havilland) DHC-8 Series Aeroplanes
AD/DHC-8/82 Autopilot Servo Engagement 2/2002
DM
Applicability: DHC-8 Series 102, 103, 106, 201, 202, 301, 311, 314 and 315, with Serial Numbers
003 through 580 inclusive.
Requirement: 1. Determine through a visual inspection of the automatic flight control system, SM-300 servo drive assemblies, Part Numbers (P/N) 7002260-922 and -923, the serial numbers (S/N) of the aileron and elevator servo drives.
Note 1: P/N 7002260-922 applies to both the elevator servo drive unit installed in Series 100, 200 and 300 aircraft and to the aileron servo drive unit installed in Series 300 aircraft.
Note 2: P/N 7002260-923 applies to the aileron servo drive units installed in Series 100 and 200 aircraft.
2. Remove and replace aileron and elevator servo drive assemblies (P/Ns 7002260- 922 and -923) that have a serial number with the last four digits in the range from 4826 through 5935 (i.e. xxxx 4826 through xxxx 5935) with servo drive assemblies complying with the following:
- If P/N 7002260-922 is removed, replace with servo drive assembly
P/N 7002260-722 or with servo drive assembly P/N 7002260-922 that has a serial number with the last four digits being 4825 or lower.
b. If P/N 7002260-923 is removed, replace with servo drive assembly
P/N 7002260-723 or with servo drive assembly P/N 7002260-923 that has a serial number with the last four digits being 4825 or lower.
Bombardier Alert Service Bulletin A8-22-18 dated 06 September 2001 or Revision A dated 18 September 2001, provides approved instructions for replacing the servo drive units.
3. Aileron and elevator servo drive assemblies (P/Ns 7002260-922 and -923) that have a serial number with the last four digits in the range from 4826 through 5935 shall not be installed in any aircraft.
Note 3: Transport Canada AD CF-2001-40 refers.
Bombardier (Boeing Canada/de Havilland) DHC-8 Series Aeroplanes
AD/DHC-8/82 (continued)
Compliance: For Requirement 1 - Before 28 December 2002.
For Requirement 2 - Before 28 December 2002.
For Requirement 3 - As of the effective date of this Directive.
This Airworthiness Directive becomes effective on 28 December 2001.
Background: A Transport Canada investigation, of an incident involving higher than normal aileron control forces, determined that screws in the SM-300 autopilot clutch assembly had backed out sufficiently, causing the clutch to mechanically engage the autopilot servo. The screws were able to back out due to the type of screw adhesive used during manufacture of the unit.
This Directive requires the replacement of affected servo drive units and limits their installation on aeroplanes as replacement parts.
Eugene Paul Holzapfel
Delegate of the Civil Aviation Safety Authority 12 December 2001
The above AD is notified in the Commonwealth of Australia Gazette on 19 December 2001.