AD/DHC-8/102 Amdt 1 Pitot Static System Contamination (Cth)

AIRWORTHINESS DIRECTIVE

On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/DHC-8/102 and issues the following 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 (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes

AD/DHC-8/102 Amdt 1 Pitot Static System Contamination 8/2008

Applicability:	Models DHC-8-400, DHC-8-401 and DHC-8-402, Serial Numbers (S/N) 4003 through 4154.
Requirement:	1.    Clean the drain hole of all the pitot static probes in accordance with Dash 8 Q400 Aircraft Maintenance Manual (AMM), PSM 1-84-2, Task 20-00-40-170-801 as follows:
Note 1:  Aircraft Serial Numbers 4147 to 4154 have had the new design probes installed during production (Bombardier ModSum 4-113525), cleaning of pitot static probe drain hole is not required on those aircraft.
a.     Clean the drain holes in accordance with paragraph 4.B., Procedure 2, sub-paragraph (1) to (3) of the AMM task.
b.    After cleaning, examine the drain hole for blockage in accordance with Paragraph 4.A., Procedure 1 of the AMM task.
c.     If the drain hole of any pitot static probe is blocked, repeat the Requirement 1.a. and 1.b. cleaning and examination procedure of this Directive on the affected pitot static probe.
2.    For aircraft S/N 4003, 4004, 4006, 4008 through 4114, clean the pitot lines in accordance with Dash 8 Q400 AMM, PSM 1-84-2, Task 34-11-00-170-801 of each aircraft that has not been modified in accordance with Requirement 3.
3.    For aircraft S/N 4003, 4004, 4006, 4008 through 4114, incorporate Bombardier ModSum 4-113488 to modify the pitot static system tubing for improved water drainage.  Bombardier Service Bulletin (SB) 84-34-59, Revision D, dated 27 July 2007, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada provides approved instructions for incorporating ModSum 4-113488.
Note 2:  Incorporation of Modsum 4-113488, before the effective date of this Amendment, in accordance with Revision A, B or C of SB 84-34-59 also satisfies this Requirement.

Accomplishment of the Requirement 3 modification constitutes terminating action to the Requirement 2 repetitive pitot line cleaning.

4.    For aircraft Serial Numbers 4003 through 4146 -

a.     Incorporate Bombardier ModSum 4-113530 to replace the left side primary pitot probe with a new design.  Bombardier SB 84-34-90, Revision B, dated 3 January 2007, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada provides approved instructions for incorporating ModSum 4-113530.

Note 3:  Incorporation of Modsum 4-113530, before the effective date of this Amendment, in accordance with the initial issue or Revision A of Bombardier SB
84-34-90 also satisfies this Requirement.

b.    Incorporate Bombardier ModSum 4-113531 to replace the right side primary pitot probe with a new design. Bombardier SB 84-34-91, Revision B, dated 10 January 2007, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada provides approved instructions for incorporating ModSum 4-113531.

Note 4:  Incorporation of Modsum 4-113531, before the effective date of this Amendment, in accordance with the initial issue or Revision A of Bombardier SB
84-34-91 also satisfies this Requirement.

5.    For aircraft Serial Numbers 4003 through 4154, incorporate Bombardier ModSum 4-113526 to replace the standby pitot probe with a new design.  Bombardier SB 84-34-93, Revision A, dated 23 February 2007, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada, provides approved instructions for incorporating ModSum 4-113526.

Note 5:  Incorporation of Modsum 4-113526, before the effective date of this Amendment, in accordance with the initial issue of Bombardier SB 84-34-93 also satisfies this Requirement.

6.    For aircraft Serial Numbers 4115 through 4145, carry out a one-time inspection for the correct installation of standby pitot static system tube assemblies and perform any necessary rectification, according to the Accomplishment Instructions of the Initial Issue of Bombardier SB 84-34-99, dated 4 April 2007, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada.

Accomplishment of the Requirement 4, 5 and 6 modifications constitutes terminating action to the Requirement 1 repetitive pitot static probe drain hole cleaning and inspections.

Note 6:  Transport Canada AD CF-2005-15R1 refers.
Compliance:	For Requirement 1 - Initially, within 30 days after 4 August 2005 (the effective date of the original issue of this Directive) and thereafter at intervals not to exceed 70 hours time in service (TIS) until Requirements 4, 5 and 6 are accomplished.
For Requirement 2 - Initially, within 30 days after 4 August 2005 the effective date of the original issue of this directive) and thereafter at intervals not to exceed 600 hours TIS until the aircraft is modified in accordance with Requirement 3.
For Requirement 3 - Within 6 000 hours TIS after the effective date of this Amendment.
For Requirement 4 - Within 6 000 hours TIS after the effective date of this Amendment.
For Requirement 5 - Within 6 000 hours TIS after the effective date of this Amendment.
For Requirement 6 - Prior to accomplishing Requirement 5.
This Amendment becomes effective on 31 July 2008.
Background:	Incidents of airspeed mismatch between the pilot, co-pilot and standby airspeed indication have been reported to Transport Canada.  These events are believed to be caused by contamination within the pitot lines and/or blockage within the pitot static probes.  Blockage of a probe’s pitot drain may allow sufficient moisture to enter the probe’s internal pitot line such that freezing may occur under certain conditions, causing a blockage to the pitot line.
The Original issue of this Directive was an interim action to avoid the potential for erroneous airspeed information, by mandating the periodic cleaning of the pitot static probe drain hole and the pitot lines.
To mitigate potential blockage of the pitot static system, Bombardier has introduced modifications to improve the water drainage capabilities of the pitot static system and the freeze protection capabilities of the pitot probes.  Therefore, this Amendment is issued to mandate the incorporation of the above-mentioned modifications as terminating action to the repetitive maintenance requirements mandated by the original issue of this Directive.

The original issue of this Directive became effective on 4 August 2005.

James Coyne
Delegate of the Civil Aviation Safety Authority

20 June 2008