AD/BAe 146/123 Lift Spoiler Actuator Corrosion (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.

British Aerospace BAe 146 Series Aeroplanes

AD/BAe 146/123 Lift Spoiler Actuator Corrosion 8/2006

Applicability:

All Models BAe 146 and AVRO 146-RJ series aeroplanes equipped with lift spoiler actuators P/N P308-45-0002 or P308-45-0102.

Requirement:

1.    (a)   Inspect the eye end assembly of aircraft lift spoiler actuators/jacks manufactured before I January 2000 or with Serial Numbers prefixed with DAWX or CSW for evidence of corrosion, damaged threads or thread fretting in accordance with Paragraph 2 of Service Bulletin 27-176 Revision 2 or later EASA approved revision.

(b)   Where lift spoiler jack eye-end assembly is found to have severe corrosion in accordance with paragraph 2.C of Service Bulletin 27-176 Revision 2 or later EASA approved revisions replace the unit.

(c)   Where lift spoiler jack eye-end assembly is found to have light corrosion in accordance with paragraph 2.C of Service Bulletin 27-176 Revision 2 or later approved revision and is re-installed, the unit must be re-inspected in accordance with paragraph 2 of Service Bulletin 27-176 Revision 2 or later approved EASA revision.

(d)   Where lift spoiler jack eye-end assembly is found to have no corrosion in accordance with paragraph 2.C. and is re-installed the unit must be re-inspected in accordance with paragraph 2 of Service Bulletin 27-176 Revision 2 or later EASA approved revision.

2.    (a)   Inspect the eye end assembly of aircraft lift spoiler jacks manufactured after 31 December 1999, excluding units with Serial Numbers prefixed with DAWX or CSW, for evidence of corrosion, damaged threads or thread fretting in accordance with Paragraph 2 of Service Bulletin 27-176 Revision 2 or later EASA approved revision.

(b)   Where lift spoiler jack eye-end assembly is found to have severe corrosion in accordance with paragraph 2.C of Service Bulletin 27-176 Revision 2 or later EASA approved revision replace the unit.

(c)   Where lift spoiler jack eye-end assembly is found to have light corrosion in accordance with paragraph 2.C of Service Bulletin 27-176 Revision 2 or later approved revision and is re-installed the unit must be re-inspected in accordance with paragraph 2 of Service Bulletin 27-176 Revision 2 or later EASA approved revision.

(d)   Where lift spoiler jack eye-end assembly is found to have no corrosion in accordance with paragraph 2.C of Service Bulletin 27-176 Revision 2 or later approved revision and is re-installed, the unit must be re-inspected in accordance with paragraph 2 of Service Bulletin 27-176 Revision 2 or later EASA approved revision.

3.    No lift spoiler jack may be installed on an aircraft without inspection for evidence of corrosion, damaged threads or thread fretting in accordance with Paragraph 2 of Service Bulletin 27-176 Revision 2 or later EASA approved revision.

Where the inspection requirements of Service Bulletin 27-1 76 original issue or revisions 1 has been carried out this may be taken for compliance with the initial inspection requirements of this Airworthiness Directive.

Note:  EASA AD 2006-0139 dated 23 May 2006 refers.

Compliance:

1.    (a)   Within 30 days after the effective date of this AD.

(b)   Prior to further flight.

(c)   Within 2 years.

(d)   Within 4 years.

2.    (a)   Within 150 days after the effective date of this AD.

(b)   Prior to further flight.

(c)   Within 2 years.

(d)   Within 4 years.

The repeat inspection requirements specified in requirements 1(c) and 1(d) or 2(c) and 2(d) of this AD must be applied from the date of initial inspection.

3.    After the effective date of this AD.

This Airworthiness Directive becomes effective on 3 August 2006.

Background:

An aircraft on approach experienced an asymmetric uncommanded deployment of a lift spoiler that resulted in a roll rate that required significant control inputs.  The failure was caused by corrosion at the thread where the eye-end was screwed into the piston of the lift spoiler actuator.

The lift spoiler actuator is most highly loaded at high flap angles with the aircraft operating near to the maximum permitted speed for that flap angle.  The most likely flight phase for this failure to occur is therefore approach or take-off and the low altitude of these flight phases provides less time in which to safely control the roll rate.

James Coyne
Delegate of the Civil Aviation Safety Authority

20 June 2006