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 na me. 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 ma y 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 Can ada, Ottawa, telephone 613 952-4357.

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### 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 Communicat ions 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 Extensi on 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 us ing 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 t he 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 subs equent 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 fr om 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 Chie f, 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 exc eed 50 hours air time or 10 calendar days, whichever occurs first, repeat the ins pection 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.