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-2012-02

Issue Date 

 9 January 2012 

Number: CF-2012-02 

Subject: Rudder Control System – Seizure of the Rudder Feel Trim Unit 

Effective: 23 January 2012 

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

4003 and subsequent, equipped with Rudder Feel Trim Unit Part Number 399500-

1007. 

Compliance: As indicated below, unless already accomplished. 

Background: There have been several reported incidents on DHC-8 Series 400 aeroplanes where the 

movement of the rudder pedals have been impeded. An investigation showed that the 

Rudder Feel Trim Unit (RFTU) trunnion shaft was corroded. The root cause of the 

corrosion was a quality escape where cadmium plating on the trunnion bushing within the 

RFTU assembly was not removed. Corrosion on the shaft and in the trunnion bushing 

seized the trunnion and caused difficulties in controlling the rudder movement. 

This condition, if not corrected, could cause a rudder control jam or a large and rapid 

alternating rudder input leading to a structural failure of the vertical fin. 

This Airworthiness Directive (AD) is issued to replace the affected RFTUs to limit the 

possibility of binding and replace the affected RFTUs with units that have been reworked 

with conformal bushings to terminate the lubrication requirements. 

Corrective 

Actions: 

A. Within 600 hours air time or six months, whichever comes first, from the effective 

date of this AD, inspect the serial number (S/N) of the RFTU in accordance with the 

Accomplishment Instructions of Bombardier Aerospace Service Bulletin (SB)

84-27-57, dated 22 July 2011, or later revisions approved by the Chief, Continuing 

Airworthiness, Transport Canada. 

1. If the RFTU’s S/N is not in the range from 0009 thru 0388 or if the S/N has a 

suffix “A”, no further action is required. 

Note: Inspection of the RFTU serial number may be conducted visually on the 

aeroplane or by checking the maintenance records. 

2. If the RFTU’s S/N is in the range from 0009 thru 0388 without a suffix “A”, 

perform an operational check of the RFTU for any sign of seizure of the trunnion 

and its bushing in accordance with the Accomplishment Instructions, 

Paragraph 3.B (Part A) step 3 of the above mentioned SB. 
No.

N° CF-2012-02 2/2 

a. If a seizure of the RFTU trunnion and its bushing is found, prior to next flight,

replace the RFTU in accordance with the Accomplishment Instructions, 

Paragraph 3.B, Part B of the above mentioned SB. 

b. If no seizure of the RFTU trunnion and its bushing is found, lubricate the 

RFTU in accordance with the Accomplishment Instructions, Paragraph 3.B, 

Part C of the above mentioned SB. Repeat the lubrication of the RFTU at 

intervals not to exceed 600 hours air time until the RFTU is replaced with a

unit that has a S/N outside of the affected range or a S/N with the suffix “A”. 

B. Within 6000 hours air time from the effective date of this AD, replace all affected 

RFTUs with units that have a S/N outside of the affected range or a S/N with the 

suffix “A” in accordance with the Accomplishment Instructions, Paragraph 3.B, Part B

of the above mentioned SB. 

C. As of the effective date of this AD, no person may install a RFTU P/N 399500-1007 

with a S/N from 0009 thru 0388 without a suffix “A” on an aeroplane. 

Authorization: For the Minister of Transport, Infrastructure and Communities 

ORIGINAL SIGNED BY

Derek Ferguson 

Chief, Continuing Airworthiness 

Contact: Mr. Gordanko Jeremic, Continuing Airworthiness, Ottawa, telephone 613-952-4357, 

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

Canada Centre.