Transport Transports 

Canada Canada

 TP 7245E

 

AIRWORTHINESS DIRECTIVE

The following airworthiness directive (AD) may be applicable to an aircraft which our records indicate is registered in your name. ADs are issued pursuant to Canadian 

Aviation Regulation (CAR) 521 Division X. Pursuant to CAR 605.84 and the further details of CAR Standard 625, Appendix H, the continuing airworthiness of a Canadian registered aircraft is contingent upon compliance with all applicable ADs. Failure to comply with the requirements of an AD may invalidate the flight authorization of the aircraft. 

Alternative means of compliance shall be applied for in accordance with CAR 605.84 and the above-referenced Standard. 

This AD has been issued by the Continuing Airworthiness Division (AARDG), National Aircraft Certification Branch, Transport Canada, Ottawa, telephone 613 952-4357.

Pursuant to CAR 202.51 the registered owner of a Canadian aircraft shall, within seven days, notify the Minister in writing of any change of his or her name or address. 

To request a change of address, contact the Civil Aviation Communications Centre (AARC) at Place de Ville, Ottawa, Ontario K1A 0N8, or 1-800-305-2059, or www.tc.gc.ca/civilaviation/communications/centre/ address.asp 

24-0022 (01-2005)

1/2 No.

CF-2011-01R1

Issue Date 

 20 May 2011 

Number: CF- 2011-01R1 

Subject: Main Landing Gear Alternate Extension System – Cam Mechanism not in Normal 

Rested Position 

Effective: 17 June 2011 

Revision: Supersedes Airworthiness Directive (AD) CF-2011-01 

Applicability: Bombardier Inc. DHC-8 Aeroplane, Models 400, 401 and 402, Serial Numbers 4001 

and subsequent 

Compliance: As indicated, unless already accomplished. 

Background: Two cases of the main landing gear (MLG) alternate extension system (AES) cam 

mechanism failure were found during line checks. The cam mechanism operates the 

cable to open the MLG door and releases the MLG uplock in sequence. In the case 

where it is necessary to deploy the MLG using the AES, the failure of the MLG AES cam 

mechanism on one side will lead to an unsafe asymmetrical landing configuration. 

Preliminary investigation indicates that the cam mechanism failure may have occurred 

and remained dormant after a previous AES operation. The cam mechanism may not 

have fully returned to the normal rested position. With the cam mechanism out of normal 

rested position, normal powered landing gear door operation could introduce sufficient 

loads to fracture the cam mechanism or rupture the door release cable. 

This directive mandates the initial and subsequent inspections for proper operation of the 

MLG AES cam mechanism, and rectify as necessary. 

Since the original issue of this directive, Bombardier Inc. has determined that the existing 

inspection procedure is insufficient for verification of proper MLG AES cam mechanism 

operation, and has superseded this inspection procedure. This revision of the directive 

mandates the use of the latest inspection procedure. 

Corrective 

Actions: 

Within 50 hours air time or 10 calendar days from the effective date of the Original Issue 

of this directive (17 January 2011), whichever occurs first: 

A. Inspect for proper operation the MLG AES cam mechanism in accordance with Part 

A of Bombardier Repair Drawing (RD) 8/4-32-0160, Issue 3, dated 12 February 

2011, or later revision approved by Chief, Continuing Airworthiness, Transport 

Canada. As of the effective date of this directive, inspection in accordance with RD 

8/4-32-0160 Issue 1, dated 14 January 2011 or Issue 2, dated 18 January 2011, no 

longer complies with the requirements of this directive. 
No.

N° CF-2011-01R1 2/2 

1. If the cam mechanism is found to reset to the normal rested position without any 

sticking or binding, it is operating properly. Proceed to paragraph B of this 

directive. 

2. If the cam mechanism has not reset to its normal rested position, or if any sticking 

or binding is observed, replace or overhaul the cam mechanism assembly in 

accordance with Part B of RD 8/4-32-0160, Issue 3, dated 12 February 2011, or 

later revision approved by Chief, Continuing Airworthiness, Transport Canada,

prior to further flight and proceed to paragraph B of this directive. 

3. If the cam mechanism is found damaged or inoperative, or if the damage is 

beyond the allowable limits specified in the above-mentioned RD, contact 

Bombardier Regional Aircraft Customer Response Center for disposition prior to 

further flight and proceed to paragraph B of this directive. 

B. Subsequently, at intervals not to exceed 50 hours air time or 10 calendar days, 

whichever occurs first, repeat the inspection specified in paragraph A of this 

directive. 

Authorization: For the Minister of Transport, Infrastructure and Communities 

ORIGINAL SIGNED BY

Derek Ferguson 

Chief, Continuing Airworthiness 

Contact: Miss Helen Tsai, Continuing Airworthiness, Ottawa, telephone 613-952-4357, facsimile 

613-996-9178 or e-mail CAWWEBFeedback@tc.gc.ca or any Transport Canada Centre.