AD/DHC-8/139 Spoiler Cable Disconnect Caution Light (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 (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes

AD/DHC-8/139 Spoiler Cable Disconnect Caution Light 4/2008

Applicability:	DHC-8-400, DHC-8-401 and DHC-8-402 model aeroplanes, Serial Numbers (S.N) 4003, 4004, 4006 and 4008 through 4129, inclusive.
Requirement:	Unless already accomplished, modify the spoiler cable disconnect sensing circuit follows:
a.     For aeroplanes S/N 4003, 4004, 4006 and 4008 through 4094, inclusive - Incorporate Modsum 4-110066.  Bombardier Service Bulletin (SB) 84-27-33, original issue dated 6 June 2007, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada, provide approved instructions for incorporating Modsum 4-110066.
b.    For aeroplanes S/N 4095 through 4129, inclusive - Incorporate Modsum 4-126356.  Bombardier SB 84-27-28, Revision B, dated 25 September 2007, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada, provide approved instructions for incorporating Modsum 4-126356.
Note 1:  Installation of Modsum 4-126356 in accordance with SB 84-27-28 original issue, dated 2 October 2006, or Revision A, dated 30 April 2007, before the effective date of this Directive is acceptable for compliance with this Directive.
Note 2:  Transport Canada AD CF-2008-13 refers.
Compliance:	Within 6000 hours time in service after the effective date of this Directive.
This Airworthiness Directive becomes effective on 10 April 2008.
Background:	All DHC-8 Series 400 aeroplanes have had a spoiler fuselage cable disconnect sensing system installed during production.  Subsequently it was discovered that, in the event of a spoiler fuselage cable disconnect, only the ROLL SPLR INBD HYD caution light will be illuminated until the aircraft speed decreases below 165 kts, at which time the ROLL SPLR OUTBD HYD caution light will also be illuminated.  In the event of a spoiler fuselage cable disconnect in association with the existing indications described above, the reduction in roll authority could result in increased pilot workload during approach and landing.

Modsums 4-110066 and 4-126356 (each applicable to a different batch of aeroplane serial numbers) have been issued to rework the sensing circuit caution light indication to ensure that it is consistent for spoiler fuselage cable disconnects above and below 165 kts.  Modsum 4-126356 has been installed in production on aircraft serial numbers 4130 and subsequent.

David Punshon
Delegate of the Civil Aviation Safety Authority

18 February 2008