Document ID: chunk:federal_register_of_legislation:F2009L02260:body:0:p2
Version: federal_register_of_legislation:F2009L02260
Segment Type: other
Provision Reference: 
Character Range: 2649–4623

after the S/N.

             Note 5:  Bombardier Service Bulletin (SB) 84-27-32, Revision A, dated 18 January 2008, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada, provides approved instructions for the removal and replacement of the PCUs and for subsequent rigging of the elevators.

             Note 6:  Previous accomplishment of Bombardier SB 84-27-32, original issue, dated 1 May 2007, meets Requirement 3 of this AD.

             Note 7:  Transport Canada AD CF-2009-16 dated 20 April 2009 refers.
Compliance:  For Requirement 1 - Within 30 days after the effective date of this AD.

             For Requirement 2 - Commencing no later than 30 days after the effective date of this AD.

             For Requirement 3 - Within 2000 flight hours or within 12 months after the effective date of this AD, whichever comes first, unless already accomplished.
             This Airworthiness Directive becomes effective on 2 July 2009.
Background:  There has been one case reported of failure of a shaft (tailstock) on an elevator PCU, P/N 390600-1007.  Continued actuation of the affected PCU caused damage to the surrounding structure.  Subsequent investigation determined that the failure was the result of a material defect and that the shafts installed on a total of 88 suspect PCUs.

             Each elevator surface has three PCUs, powered by separate independent hydraulic systems, and a single elevator PCU shaft failure may remain dormant.  Such a dormant loss of redundancy, coupled with the potential for a failed shaft to produce collateral damage, including damage to hydraulic lines, could possibly affect the controllability of the aircraft.

             This AD mandates an identification check for elevator PCU serial numbers, a daily check for correct operation of all suspect PCUs and, finally, replacement of all suspect PCUs.

James Coyne
Delegate of the Civil Aviation Safety Authority

22 May 2009