AD/CL-600/107 Angle of Attack Transducer (Cth)

AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.001(1) of CASR 1998.  The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Bombardier (Canadair) CL-600 (Challenger) Series Aeroplanes

AD/CL-600/107 Angle of Attack Transducer 3/2009

Applicability:	Model CL-600-2B19 aeroplanes, serial number 7003 and subsequent, equipped with Thales Angle of Attack (AOA) transducers.
Requirement:	1.    Perform the following in accordance with the Accomplishment Instructions of Bombardier Service Bulletin (SB) 601R-27-154 dated 1 December 2008 or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada:
a.     Inspect the serial number of each of the AOA transducers part number (P/N) 45150340 or P/N C16258AA installed on the aircraft.  If the serial number is not listed in paragraph 1. A.(1) of SB 601R-27-154 or if a different part number is installed, no further action is required in response to this Requirement.
b.    If the P/N and serial number are listed in one of the tables in paragraph 1.A.(1) of SB 601R-27-154 and has a suffix “A” (refer Thales SB 45150340-31-004 and C16258A 27 002 both dated 28 November 2008), no further action is required in response to this Requirement.
c.     If the P/N and serial number are listed in one of the tables in paragraph 1.A.(1) of SB 601R-27-154, replace the AOA transducer in accordance with the Accomplishment Instructions, Part B, of the SB.
2.    AOA transducers P/N 45150340 or P/N C16258AA with a serial number listed in paragraph 1.A.(1) of Bombardier SB 601R-27-154 may not be installed as a replacement part unless the serial number has the suffix “A” (refer Thales SB 45150340 31 004 and C16258A-27-002).
3.    Measure the inrush current of the installed angle of attack transducers in accordance with the Accomplishment Instructions, Part A, of Bombardier SB 601R-27-153 dated 17 October 2008 or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada.
4.    If the installed AOA transducers inspected as per Table 1 have an inrush current below 1.60 Amps, replace them in accordance with the Accomplishment Instructions Part C of Bombardier SB 601R-27-153 dated 17 October 2008 or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada.

5.    If both installed AOA transducers inspected as per Table 1 have an inrush current 1.60 amps or above, repeat the Requirement 3 inspection.
6.    If both installed AOA transducers inspected per Table 1 have an inrush current below 1.60 amps, accomplish either of the following actions:
a.     Replace one of the two vanes on the aircraft with a serviceable unit and replace the other vane within 1000 hours time in service (TIS) after the inspection, or
Note 1:  If both AOA transducers are degraded (below 1.6 Amps) only one needs to be replaced and the aircraft may be dispatched with one serviceable unit for a period of 1000 hours TIS.
b.    Dispatch the aircraft for a maximum of 1000 hours TIS with the following limitations:
(i)    Operations are not conducted in visible moisture (including standing water and slush) in any form,
(ii)   Operations are not conducted in known or forecast icing conditions,
(iii)  Both Ice Detection Systems are operative; and
(iv)  Operations are conducted in day VMC conditions only.
Note 2:  Transport Canada AD CF-2008-35 refers.
Compliance:	For Requirement 1 - Within 900 hours TIS from the effective date of this Directive.
For Requirement 2 - As of the effective date of this Directive.
For Requirement 3 - As specified in Table 1.
Table 1
Accumulated Angle of Attack Transducer Hours Time in Service (TIS) on the Effective Date of this Directive	Compliance Schedule for Inrush Current Inspection
Less than 6500 hours	Before the AOA transducer has 7500 hours TIS
More than or equal to 6500 hours but not greater than 7500 hours	Within 1000 hours TIS from the effective date of this Directive but no later than 7750 hours TIS has accumulated

More than 7500 hours

Within 250 hours TIS from the effective date of this Directive

For Requirement 4 - Within 1000 hours TIS from the effective date of this Directive, then repeat the Requirement 3 inspection of the transducers in accordance with the schedule in Table 2.

For Requirement 5 - In accordance with the schedule in Table 2.

For Requirement 6.a. - Before further flight and then repeat the Requirement 3 inspection of the transducers in accordance with the schedule in Table 2.

For Requirement 6.b. - Before further flight up to a maximum of 1000 hours TIS.

Table 2

Last Angle of Attack Inrush Current
Measurement (Amps)

Compliance Schedule for Repeat
Inspections

More or equal to 1.90

Within 2000 TIS after the last measurement

More than or equal to 1.80 but less than 1.90

Within 1500 TIS after the last measurement

More than or equal to 1.70 but less than 1.80

Within 1000 TIS after the last measurement

More than or equal to 1.60 but less than 1.70

Within 500 TIS after the last measurement

This Airworthiness Directive becomes effective on 12 March 2009.

Background:

The heating capabilities of several AOA transducer heating elements removed from in-service aircraft have been found to be below the minimum requirement.  Also, it was discovered that a large number of AOA transducers repaired in an approved maintenance facility were not calibrated accurately.

Inaccurate calibration of the AOA transducer and/or degraded AOA transducer heating elements can result in early or late activation of the stall warning, stick shaker and stick pusher by the Stall Protection Computer (SPC).

This Directive mandates a periodic inspection of the inrush current to verify the AOA heating capability and replacement of the inaccurately calibrated AOA transducers.

James Coyne
Delegate of the Civil Aviation Safety Authority

27 January 2009