AD/Cessna 750/2 Chafing of APU Fuel Tube Assembly (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.

Cessna 750 (Citation X) Series Aeroplanes

AD/CESSNA 750/2 Chafing of APU Fuel Tube Assembly 7/2005 DM

Applicability:

Cessna Model 750 Aircraft, Serial Numbers -0001 through -0240 inclusive.

Requirement:

1.    Perform a detailed inspection to verify the clearance and detect chafing of one of the Auxiliary Power Unit (APU) fuel tube assemblies in the tail cone area of the airplane due to the interference between the APU fuel tube and elevator flight control cables, hydraulic lines, and high temperature bleed air couplings as per provisions of Cessna Alert Service Letter (ASL) ASL750-49-09 Revision 2, dated 10 March 2005 or later FAA approved revisions.

2.    If chafing is detected, carry out corrective action per ASL750-49-09 Revision 2 or later FAA approved revisions.

3.    For airplanes having serial numbers -0001 through -0031 inclusive and -0033 through -0107 inclusive, replace the APU fuel tube in the tail cone area of the airplane with a new fuel tube Part Number 6756605-23, in accordance with Cessna Service Bulletin (SB) 750-49-05 Revision 1, dated 17 January 2000 or later FAA approved revision.

Note:  FAA Airworthiness Directive (AD) 2005-09-01amendment 39-14069 dated 25 April 2005 refers.

Compliance:

1.    Within 25 flight hours or 48 days, whichever occurs first, after the effective date of this AD and then, repetitively at intervals not to exceed 250 flight hours or 3 months whichever occurs first.

2.    Before further flight.

3.    Within 25 flight hours or 48 days, whichever occurs first, after the effective date of this AD, but before carrying out inspection per Requirement 1 of this AD.

This Airworthiness Directive becomes effective on 25 May 2005.

Background:

There have been reports of chafed APU fuel tubes leaking into the tail cone area due to the interference between the fuel tube assembly and elevator flight control cables, hydraulic lines, and high temperature bleed air couplings.  It is an area where ignition sources are present and there are no fire detection or extinguishing provisions.  This interference and the resultant chafing may cause fuel leak and a fire.

The actions specified in this AD address the safety risks associated with fire and resultant loss of aircraft.

For certain aircraft serial numbers, this AD also requires replacing the APU fuel line.

James Coyne
Delegate of the Civil Aviation Safety Authority

20 May 2005