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)

1/1 No.

CF-2013-38

Issue Date 

 28 November 2013 

Number: CF-2013-38 

Subject: Design Deficiency of the Nose Wheel Steering Control Unit 

Effective: 12 December 2013 

Applicability: Bombardier Inc. model DHC-8-400, -401 and -402 aeroplanes, serial numbers 4001 

through 4448. 

Compliance: Within 2000 flight cycles or 12 months, whichever occurs first, from the effective 

date of this AD, unless already accomplished. 

Background: There has been one in-service report of an un-commanded and un-annunciated nose 

wheel steering during aeroplane push-back from the gate. The investigation revealed that 

a design deficiency exists within the steering control unit (SCU) where an open circuit 

may not be adequately detected and annunciated to the flight crew. A sustained open 

circuit could result in an un-commanded and un-annunciated nose wheel steering input. 

Un-commanded nose wheel steering during takeoff or landing may lead to a runway 

excursion. 

This AD mandates the installation of new cable assemblies, with a pull-down resistor, to 

ensure that the nose wheel steering system reverts to fail-safe free castor mode in the 

event of an open circuit in the steering system. 

Corrective 

Actions: 

Incorporate Bombardier Modsum 4-126585. Bombardier Service Bulletin (SB) 84-32-122, 

Revision A, dated 4 October 2013, or later revisions approved by the Chief, Continuing 

Airworthiness, Transport Canada, provides approved instructions for incorporating 

Modsum 4-126585. 

Incorporation of Modsum 4-126585 in accordance with the Initial Issue of SB 84-32-122, 

dated 28 August 2013, also satisfies the requirements of this AD. 

Authorization: For the Minister of Transport, 

ORIGINAL SIGNED BY 

Derek Ferguson 

Chief, Continuing Airworthiness 

Contact: Robert Farinas, Continuing Airworthiness, Ottawa, telephone 613-952-4357, facsimile 

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