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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. 

URGENT URGENT URGENT URGENT URGENT URGENT URGENT URGENT URGENT

TRANSPORT CANADA EMERGENCY AIRWORTHINESS DIRECTIVE 

PLEASE FORWARD IMMEDIATELY TO THE PERSON RESPONSIBLE FOR THE 

OPERATION AND MAINTENANCE OF YOUR AIRCRAFT

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-2011-01

Issue Date 

 17 January 2011 

Number: CF- 2011-01 

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

Rested Position

Effective: Upon Receipt 

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. 

Corrective 

Actions: 

Within 50 hours air time or 10 calendar days from the effective date of this directive, 

whichever occurs first: 

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

Part A of Bombardier Repair Drawing (RD) 8/4-32-0160, Issue 1, dated 14 January 

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

Canada. 

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. 
No.

 N° CF-2011-01 2/2 

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

sticking or binding is observed, remove and repair the cam mechanism assembly 

in accordance with Part B of the above-mentioned RD 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 repairs required 

by paragraph A.2 of this directive cannot be accomplished, 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.