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)

1/3 No.

CF-2010-05

Issue Date 

2 February 2010 

Number: CF-2010-05 

Subject: Angle of Attack Vane - Heating Element Ageing and Resolver Oil Contamination 

Effective: 26 February 2010 

Applicability: All Bombardier Inc. DHC-8 Aircraft, Models 400, 401 and 402, equipped with Thales 

Angle of Attack (AOA) vanes, Part Number (P/N) C16177AC. 

Compliance: As indicated unless already accomplished. 

Background: Although there have been no in-service reported incidents related to AOA failures on the 

DHC-8 Series 400 aeroplanes, two separate issues have been identified that would 

affect proper operation of the AOA vane, P/N C16177AC. These issues are: 

 

1. A potential freezing of the AOA Vane Resolver, which may restrict the dynamic 

behavior (lag) of the vane and could lead to a potential seize-up condition at lower 

temperatures. This condition, if not corrected, may provide inaccurate AOA data to 

the Stall Protection System (SPS). 

2. As a result of ageing, the AOA vane heating element could degrade to a point where 

there is insufficient heat to prevent ice build-up on the AOA vanes. The ice build-up 

may lead to a change in the aerodynamic properties of the AOA vane and, under 

certain conditions, send inaccurate information to the SPS. This ageing condition 

cannot be detected by the aircraft AOA vane heater current monitor. 

This directive mandates replacement of the vanes equipped with suspect resolvers and a 

periodic inspection of the in-rush current to verify the AOA vane heating capability. 

Corrective 

Actions: 

1. AOA Vane Resolver Freezing: 

Within 250 hours air time from the effective date of this directive, inspect the serial 

number (S/N) of each of the AOA vanes P/N C16177AC installed on the aeroplane in 

accordance with paragraph 1.A., Table 1 of Bombardier Service Bulletin (SB) A84-27-51, 

dated 22 December 2009, or later revisions approved by the Chief, Continuing 

Airworthiness, Transport Canada. 

1.1 If the S/N is not listed in the above-mentioned SB or its later revisions 

approved by the Chief, Continuing Airworthiness, Transport Canada, proceed 

to Paragraph 2 of this directive. 

1.2 If the S/N is listed in the above-mentioned SB or its later revisions approved by 

the Chief, Continuing Airworthiness, Transport Canada, and the S/N has a 

suffix “B”, proceed to Paragraph 2 of this directive. 
No.

 N° CF-2010-05 2/3 

1.3 If the S/N of both installed AOA vanes are listed in the above-mentioned SB or 

its later revisions approved by the Chief, Continuing Airworthiness, Transport 

Canada,, accomplish one of the following: 

1.3.1 Before further flight replace the AOA vanes in accordance with the 

Accomplishment Instructions, Part 3 of the above-mentioned SB or its 

later revisions approved by the Chief, Continuing Airworthiness, 

Transport Canada, or 

1.3.2 Before further flight, replace one of the two vanes on the aircraft with a 

serviceable unit in accordance with the Accomplishment Instructions, 

Part 3 of the above-mentioned SB. The aircraft may be dispatched with 

one serviceable unit for a maximum of 1000 hours. 

1.4 If the S/N of only one of the installed AOA vane is listed in the above-mentioned 

SB, or later revisions approved by the Chief, Continuing Airworthiness, 

Transport Canada, replace this vane within 1000 hours air time. 

NOTE: Part 1 of this directive may be accomplished visually by verifying vane S/N on 

the aeroplane or by reviewing the maintenance records. 

2. AOA Vane Heating Element Degradation: 

2.1. Inspection for In-rush current: 

In accordance with the schedule in Table A below, measure the In-rush current 

of the installed AOA vane in accordance with the Accomplishment Instructions, 

Part 3, of Bombardier SB A84-27-46, dated 20 October 2009, or later revisions 

approved by the Chief, Continuing Airworthiness, Transport Canada 

Table A 

Accumulated Angle of Attack Vane 

Hours Air Time on the Effective 

Date of this directive. 

Compliance Schedule for Initial In-rush 

Current Inspection 

Less than 5 000 hours air time Before the AOA transducer has 5 900 hours 

air time 

More than or equal to 5 000 but not 

greater than 6 000 hours air time 

Within 900 hours air time from the effective 

date of this directive but no later than 6 500 

hours air time 

More than 6 000 hours air time Within 500 hours air time from the effective 

date of this directive 

2.2 Replacement and Repeat Inspection Requirements 

2.2.1 If the installed AOA vanes, having been inspected as per schedule in 

Table A, have an In-rush current less than or equal to 1.6 Amps, replace 

them before next flight in accordance with the Accomplishment 

Instructions of the Bombardier SB A84-27-46, Part 3, dated 20 October 

2009, or later revisions approved by the Chief, Continuing Airworthiness, 

Transport Canada. Repeat the inspection of the newly installed vanes in 

accordance with the schedule in Table B of this directive. 

2.2.2 If the AOA vanes, having been inspected as per Table A, have an In-rush 

current more than 1.6 Amps, repeat the inspection of the vanes in 

accordance with the schedule in Table B of this directive. 
No.

 N° CF-2010-05 3/3 

Table B 

Last Angle of Attack In-rush Current 

Measurement (Amps) 

Compliance Schedule for Repeat 

Inspection 

Less than or equal to 1.6 Amps Replace the vane before next flight 

More than 1.60 Amps but less than or 

equal to 1.70 Amps 

Repeat the inspection within 1 000 hours 

air time 

More than 1.70 Amps Repeat inspection within 2 000 hours air 

time 

New AOA vane Within 2 000 hours air time after the 

installation date 

NOTE: Replacement AOA vanes must be either outside the affected S/N identified in 

paragraph 1.A., Table 1 of the SB A84-27-51, dated 22 December 2009, or 

later revisions approved by the Chief, Continuing Airworthiness, Transport 

Canada, or identified as having been tested by a suffix "B" after the S/N. 

3. AOA Vane Replacement 

As of the effective date of this directive, no replacement of AOA vanes 

P/N C16177AC, with S/N listed in paragraph 1.A., Table 1 of Bombardier 

SB A84-27-51, dated 22 December, 2009, or later revisions approved by the Chief, 

Continuing Airworthiness, Transport Canada, are allowed to be installed on DHC-8 

Series 400 aeroplanes unless such vane has been inspected by the manufacturer 

and labeled with a suffix “B” after the S/N. 

Authorization: For Minister of Transport, Infrastructure and Communities 

ORIGINAL SIGNED BY 

Derek Ferguson 

Chief, Continuing Airworthiness 

Contact: 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.