AD/F100/89 Flight Warning Computer (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.

Fokker F100 (F28 Mk 100) Series Aeroplanes

AD/F100/89 Flight Warning Computer 8/2008

Applicability:	F28 Mark 0100 aircraft, all serial numbers, and F28 Mark 0070 aircraft serial numbers 11521, 11528 through 11537, 11545, 11547, 11553, 11557, 11561, 11562, 11566, 11567, 11571, 11572, 11576 through 11579, 11581 through 11583 (all fitted with centre wing fuel tank).
Requirement:	1.    Remove Flight Warning Computer (FWC) units with part number (P/N) 80-0610-3-45 and P/N 80-0610-3-50 from the aircraft and replace with modified units with P/N 80-0610-3-55 in accordance with the Accomplishment Instructions of Fokker Services SBF100-31-067 dated 31 January 2008 or later revision approved by the European Aviation Safety Agency (EASA).
2.    Amend the Airplane Flight Manual (AFM) as specified in Fokker Services Manual Change Notification - Operational Documentation (MCNO) F100-050 dated 31 January 2008 or using AFM pages supplied by Fokker Services.
3.    FWC units having P/N 80-0610-3-45 or P/N 80-0610-3-50 may not be installed as a replacement on any aircraft that has previously complied with Requirement 1 and 2, unless it has been modified to P/N 80-0610-3-55 standard in accordance with Honeywell SB 80-0610-31-0003 dated 13 February 2008.
Note:  EASA AD 2008-0090 dated 13 May 2008 refers.
Compliance:	For Requirement 1 - Within 36 calendar months after the effective date of this Directive.
For Requirement 2 - Concurrent with the accomplishment of the Requirement 1 replacement of the FWC unit.
For Requirement 3 - After accomplishment of the Requirement 1 replacement of the FWC unit.
This Airworthiness Directive becomes effective on 31 July 2008.

Background:

A recent design review has been carried out on the F28 Mark 0070/0100 fuel system in accordance with the guidelines related to FAA SFAR 88 (Fuel Tank Safety Program) and JAA INT/POL/25/12.  The review revealed that under certain failure conditions, prolonged dry running of the fuel transfer pumps may result in an ignition source in the centre wing fuel tank.  This condition, if not corrected, could lead to ignition of flammable fuel vapours, resulting in fuel tank explosion and consequent loss of the aircraft.

To address and correct this unsafe condition, new software (version V13.55) has been developed for the FWC.  This software update introduces a decreased time delay of the centre wing fuel tank low pressure alert from 15 minutes to 60 seconds, to stop prolonged dry running of the fuel transfer pumps.

James Coyne
Delegate of the Civil Aviation Safety Authority

13 June 2008