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 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 b y the Continuin g Airworthiness Division ( AARDG ) , National Aircraft Certification Branch, Trans p ort Canada, Ottawa, tele p hone 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 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/ addr ess.asp 2 4-0022 ( 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 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 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 subs equent 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 ve rification of proper MLG AES cam mechanism operation, and has superseded this inspection pr ocedure. 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 ca m 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 Chie f, Continuing Airworthiness, Transport Canada. As of the effective date of this di rective, 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 require ments 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 it s normal rested position, or if any sticking or binding is observed, replace or ov erhaul 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 Re sponse 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.