AD/B747/326 Flap Control Unit (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.

Boeing 747 Series Aeroplanes

AD/B747/326 Flap Control Unit 5/2005

Applicability:	Model 747-400, -400D and -400F series aeroplanes, identified in Boeing Alert Service Bulletin (ASB) 747-27A2386, dated 13 March 2003.
Requirement:	1.    Replace at least one flap control unit (FCU) having part number (P/N) 285U0011-207 with a new or modified FCU having P/N 285U0011-208 in accordance with the Accomplishment Instructions of ASB 747-27A2386.
Note 1:  ASB 747-27A2386 refers to Boeing Component Service Bulletin (CSB) 285U0011-27- 06, dated 13 March 2003, as an additional source of service information for modifying an FCU having P/N 285U0011-207 to P/N 285U0011-208.
2.    For aeroplanes identified in Boeing Service Bulletin (SB) 747-27- 2319, dated 24 January 1991 - Replace the three FCUs having P/N 285U0011-205 or 285U0011-206 with new or modified FCUs having P/N 285U0011-207 in accordance with the Accomplishment Instructions of SB 747-27-2319.
Note 2:  SB 747-27-2319 refers to Boeing CSB 285U0011-27-04, dated 24 January 1991, as an additional source of service information for modifying the FCUs having P/N 285U0011-205 or 285U0011-206 to P/N 285U0011-207.
3.    FCUs P/N 285U0011-205 or -206 may not be installed on any aeroplane as a replacement part.
Note 3:  FAA AD 2005-04-03 Amdt 39-13975 refers.
Compliance:	For Requirement 1 - At the earlier of the intervals specified below:
a.     Within 60 months after the effective date of this Directive,
b.    Within 25,000 hours time in service after the effective date of this Directive, or
c.     Within 4,000 flight cycles after the effective date of this Directive.
For Requirement 2 - Before or concurrent with the accomplishment of Requirement 1.
For Requirement 3 - As of the effective date of this Directive.

This Airworthiness Directive becomes effective on 12 May 2005.

Background:

This Directive requires replacing at least one FCU in the main equipment centre with a new or modified FCU.

This action is designed to prevent disconnection of autoland/autopilot functions and loss of primary flaps control and flaps indication display due to disengagement of all three FCUs at the same time.  Disengagement of all three FCUs at the same time, could lead to a non-normal high speed landing with the flaps retracted, increased pilot workload and possible runway departure at high speeds during landing.

James Coyne
Delegate of the Civil Aviation Safety Authority

31 March 2005