AD/DHC-3/40 Amdt 1 Elevator Servo-Tab Assembly (Cth)

AIRWORTHINESS DIRECTIVE

On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/DHC-3/40 and issues the following AD under subregulation 39.001(1) of CASR 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.

DHC-3 (Otter) Series Aeroplanes

AD/DHC-3/40 Amdt 1 Elevator Servo-Tab Assembly 8/2008

Applicability:

All Model DHC-3 aircraft with any of the following Supplemental Type Certificates (STC) installed: SA01-111; SA89-32; or SA02-15 for turbine engines or STC
SA83-18 for the PZL ASZ-621R-M18 engine.

Requirement:

Install one of the following elevator flutter prevention kits:

a.    Viking Air Ltd. Retro Kit No. V3MK1148 Issue 3, or later Transport Canada approved revision; in accordance with Viking Air Ltd. STC SA99-219 Issue 3, or later Transport Canada approved revision;

b.    American Automotives Inc STC No. SA03-99 (FAA STC No. SA01059SE) with new elevator servo-tab and redundant control linkage; or

c.    Other modifications, approved by Transport Canada, designed to prevent the elevator servo-tab flutter.

Note:  Transport Canada AD CF-2006-02R1 refers.

Compliance:

Unless already accomplished, within 300 flight hours or 6 months after 31 July 2008, whichever occurs first.

This Amendment becomes effective on 31 July 2008.

Background:

Transport Canada received several reports of incidents on turbine-powered DHC-3 aircraft whereby the control rod of the elevator servo-tab system detached from the servo-tab.  This failure can cause severe flutter of the elevator servo-tab and could lead to loss of control of the aircraft.

Turbine engines are more powerful, allow for a higher cruise speed, and therefore may reduce the elevator servo-tab flutter margins.  This Directive requires installation of a kit to reduce the probability of elevator servo-tab failure due to flutter.

Amendment 1 is issued in response to a revision of the related Transport Canada AD which was prompted, following a review of the service history of all Model DHC-3 aircraft, that those aircraft with the higher powered PZL ASZ-621R-M18 reciprocating radial engine installed (STC SA83-18) could reach cruise speeds similar to the turbine powered aircraft.

David Villiers
Delegate of the Civil Aviation Safety Authority

12 June 2008