AD/F100/75 High Pressure Compressor (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/F100/75 High Pressure Compressor 3/2006

Applicability:

Fokker Aircraft B.V. Model F28 Mark 0070 and Mark 0100 aircraft, all serial numbers, if equipped with Rolls-Royce (Deutschland) Tay620 or Tay650 series engines in pre-SB TAY-72-1653 configuration.

Requirement:

1.    Incorporate the minimum vane tip clearance modification on both engines of the aircraft in accordance with Rolls-Royce Deutschland (RRD) Service Bulletin (SB) TAY-72-1653 dated 29 August 2005 or a later EASA approved revision;

2.    No engine may be installed in any F28 Mark 0070 or Mark 0100 aircraft, unless it has been modified in accordance with RRD SB TAY-72-1653.

Note:  Civil Aviation Authority Netherlands Airworthiness Directive Nr. NL-2005-014 EASA Approval No. 2005-6404 dated 10 November 2005 refers.

Compliance:

1.    At the next scheduled shop visit for each engine, but not later than
1 January 2010.

2.    After 1 January 1 2010.

This Airworthiness Directive becomes effective on 16 March 2006.

Background: Between 1991 and the end of 2004, 39 Rolls-Royce Tay (all marks) engines have experienced heavy rubbing between the High Pressure Compressor (HPC) stator vane tips and the corresponding HPC rotor spacer, causing partial loss of HPC rotor spacer material.  Investigation revealed that HPC spacer rubbing occurs due to thermal and aircraft manoeuvre induced closure of the vane tip-to-spacer gap on engines where the gap was close to the minimum vane tip clearance which is applicable during engine build-up.  Nine of the referenced events resulted in a commanded In-Flight Shut-Down (IFSD).  There are also indications that some of these events resulted in partial or total loss of thrust control (LOTC), due to engine stall/stagnation and/or high Turbine Gas Temperature (TGT).  This condition, if not corrected, may cause further events of spacer material loss, potentially reducing the surge margin and resulting in HPC surge events and subsequently to LOTC or IFSD.

James Coyne
Delegate of the Civil Aviation Safety Authority

1 February 2006