AD/CL-600/120 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-600/120 Angle of Attack Transducer 11/2009

Applicability:	Model CL-600-2C10, CL-600-2D15 and CL-600-2D24 aircraft equipped with Thales Angle of Attack (AOA) transducers, part number (P/N) C16258AA.
Requirement:	1.    Inspect the part number and the serial number (S/N) of each of the AOA transducers P/N C16258AA installed on the aircraft in accordance with the Accomplishment Instructions of Bombardier Service Bulletin (SB) 670BA-27-053, dated 14 May 2009.  If the conditions specified in sub-paragraphs a. or b. below are found during this inspection no further action is necessary.
a.     If the S/N is not listed in paragraph 1. A.(1) of SB 670BA-27-053 or if a different part number is installed.
b.    If the P/N and the S/N are listed in paragraph 1.A.(1) of SB 670BA-27-053 and the serial number has a suffix “A” (refer Thales SB C16258A-27-002).
2.    If the P/N and the S/N are listed in paragraph 1.A.(1) of SB 670BA-27-053, replace the AOA transducer in accordance with the Accomplishment Instructions, Part 2 Paragraph B.(2) of SB 670BA-27-053.
3.    AOA Transducers P/N C16258AA with a S/N listed in paragraph 1.A.(1) of SB 670BA-27-053, may not be installed on any aeroplane as a replacement spare unless the serial number has the suffix “A” (refer Thales SB C16258A-27-002).
4.    Measure the inrush current of the installed AOA transducers in accordance with the Accomplishment Instructions, Part A, of Bombardier SB 670BA-27-051, dated 14 May 2009.
5.    If the installed AOA transducers, inspected as per Requirement 4, have an inrush current less than 1.60 Amps, replace them in accordance with the Accomplishment Instructions, Paragraph 2, Part C, of Bombardier SB 670BA-27-051.
6.    Measure the inrush current in accordance with the Accomplishment Instructions, Part A, of Bombardier SB 670BA-27-051 of any AOA transducers newly installed in accordance with Requirement 5.

7.    If the AOA transducers, inspected per Requirement 4, have an inrush current more than or equal to 1.60 Amps, repeat the Requirement 4 inspection.
Later revisions of the above Service Bulletins approved by the Chief, Continuing Airworthiness, Transport Canada are acceptable for compliance with the relative requirements of this Directive.
Note:  Transport Canada AD CF-2009-35 refers.
Compliance:	For Requirement 1 - Within 6,000 time in service (TIS) after the effective date of this Directive.
For Requirement 2 - Before further flight after the Requirement 1 inspection.
For Requirement 3 - As of the effective date of this Directive.
For Requirement 4 - As per Table 1.
Table 1
Accumulated Angle of Attack Transducer Hours TIS on the Effective Date of this Directive.	Compliance Schedule for Initial Inrush Current Inspection
Less than 6,500 hours TIS	Before the AOA transducer has 7,500 hours TIS
More than or equal to 6,500 but not greater than 7,500 hours TIS	Within 500 hours TIS from the effective date of this Directive but no later than 8,000 hours air time
More than or equal to 7,500 hours TIS	Within 250 hours TIS from the effective date of this Directive
For Requirement 5 - Before further flight after the Requirement 4 inspection / measurement.
For Requirement 6 - Within 2,000 hours TIS after the installation date and thereafter at the intervals specified in Table 2.
For Requirement 7 - At the intervals specified in Table 2.

Table 2

Last Angle of Attack Inrush
Current Measurement (Amps)

Compliance Schedule for
Repeat Inspection

More than or equal to 1.90

Within 2,000 hours TIS after the last measurement

More than or equal to 1.80 but less than 1.90

Within 1,500 hours TIS after the last measurement

More than or equal to 1.70 but less than 1.80

Within 1,000 hours TIS after the last measurement

More than or equal to 1.60 but less than 1.70

Within 500 hours TIS after the last measurement

This Airworthiness Directive becomes effective on 22 October 2009.

Background:

The heating capability of several AOA transducer heating elements removed from in-service aircraft has been found to be below the minimum requirement.  It was also 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

10 September 2009