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 39.1 (1) of CAR 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.

AlliedSignal (Garrett/AiResearch) Turbine Engines - TPE331 Series

AD/TPE331/60 Cycle Life Counting - Special Use Operations 2/2003

DM

Applicability: Honeywell TPE331-1, -2, -3, -5, -6 turboprop engines with turbine wheels installed that have been engaged at any time in special use operations.

For the purpose of this directive, special use operations are defined as performing multiple take-offs and landings for each engine start/shutdown cycle.

Note 1: TPE331-1, -2, -3, -5, -6 powered aircraft types known to be applicable include, but may not be limited to; Air Tractor AT 301 conversions, Ayres S2R-G6, Rockwell S-2R conversions, Airparts FU-24 Stallions, Shorts SC7 Skyvans and De Havilland Canada DHC-2 conversions.

Requirement: Carry out a review of aircraft and engine records, determine if the installed turbine wheels are applicable and, if so, in accordance with Honeywell Alert Service Bulletin TPE331-A72-2111, calculate equivalent and total equivalent turbine wheel cycles based on the number of aircraft take-offs and landings per engine cycle.

Remove applicable turbine wheels from service in accordance with Table 1 of Honeywell Alert Service Bulletin TPE331-A72-2111.

In the absence of aircraft records detailing the number of take-offs and landings per engine cycle prior to the effective date of this directive, a ratio of six take-offs and landings per engine major cycle shall be used to determine equivalent cycles and total equivalent cycles.

Note 2: Honeywell Service Bulletin TPE331-A72-2111 defines engine cycles, major cycles, equivalent cycles and total equivalent cycles.

Note 3: This directive Complements AD/ENG/7 which requires the recording of turbine engine cycles and the replacement of life limited turbine engine components in accordance with the applicable engine manufacturer’s service documents detailing such life limits.

Compliance: Requirement 1. Calculation of cycles: Within 10 hours aircraft time in service or prior to 31 January 2003, whichever occurs first.

Requirement 2. Removal of time limited components: Effective on compliance with Requirement 1.

AlliedSignal (Garrett/AiResearch) Turbine Engines - TPE331 Series

AD/TPE331/60 (continued)

This Airworthiness Directive becomes effective on 2 January 2003.

Background: This directive has been issued in response to a recent TPE331-6 uncontained turbine failure event in Australia. The investigation of that event disclosed the 2nd stage turbine wheel had fractured across the wheel web. Metallurgical examination of the fracture surface by the manufacturer determined the wheel had failed from low cycle fatigue.

Whilst the wheel had an accurately recorded 2034 engine cycles in service out of a published life limit of 5400 cycles, the engine had been engaged in multiple take-offs and landings between each engine start and shut down, now referred to by the engine manufacturer as special use operations. With a revised cycle count in accordance with that detailed in SB TPE331-A72-2111, the failed wheel was determined to have a total cycles in service of 17,085 cycles, well above the 5,400 published cycle life limit.

The event fo llows several other reports of uncontained turbine failures that have been attributed to minor cycle fatigue damage resulting from multiple take-offs and landings between each engine start and shut down. In response, the engine manufacturer has revised the procedure for calculating the cycles in service for certain turbine wheels installed in TPE331-1 through -6 engines when installed in aircraft conducting special use operations. The revised cycle count procedure is detailed in Honeywell Service Bulletin TPE331-A72-2111.

Neville James Probert

Delegate of the Civil Aviation Safety Authority 23 December 2002

The above AD is notified in the Commonwealth of Australia Gazette on 2 January 2003.