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.
Overview
The Civil Aviation Safety Authority (CASA) introduced the Airworthiness Directive (AD) for AlliedSignal (Garrett/AiResearch) Turbine Engines - TPE331 Series on 2 January 2003. This legislative instrument was issued in response to a reported uncontained turbine failure event involving a TPE331-6 engine in Australia, which highlighted a significant safety concern related to the fatigue life of turbine wheels used in special use operations. Special use operations, as defined in the directive, involve performing multiple take-offs and landings for each engine start/shutdown cycle. The AD mandates a review of aircraft and engine records to determine the applicability of installed turbine wheels and requires the calculation of equivalent and total equivalent turbine wheel cycles based on the number of take-offs and landings per engine cycle. If applicable, turbine wheels must be removed from service in accordance with the specified requirements. The directive aims to mitigate the risk of uncontained turbine failures by ensuring that the life limits of turbine wheels are accurately calculated and adhered to, thereby enhancing the safety of aircraft operations involving TPE331 engines.
Scope and Application
The Airworthiness Directive issued by the Civil Aviation Safety Authority (CASA) under subregulation 39.1 (1) of the Civil Aviation Regulations 1998 pertains specifically to the Honeywell TPE331 Series of turboprop engines with turbine wheels installed that have been engaged in special use operations. This encompasses the TPE331-1, -2, -3, -5, -6 models, and applies to aircraft types such as 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, among others. Special use operations are defined as those involving multiple take-offs and landings for each engine start/shutdown cycle. The directive requires a review of aircraft and engine records to determine if the installed turbine wheels are applicable and, if so, to calculate equivalent and total equivalent turbine wheel cycles based on the number of take-offs and landings per engine cycle, following the guidelines in Honeywell Alert Service Bulletin TPE331-A72-2111. Applicable turbine wheels must be removed from service in accordance with the specified table in the service bulletin. If detailed aircraft records are unavailable, a ratio of six take-offs and landings per engine major cycle should be used to determine the equivalent cycles and total equivalent cycles. The directive complements AD/ENG/7 which mandates the recording of turbine engine cycles and the replacement of life-limited turbine engine components. The directive is effective from 2 January 2003, and compliance must be achieved within 10 hours of aircraft time in service or before 31 January 2003, whichever occurs first. This Airworthiness Directive was issued in response to a recent uncontained turbine failure event in Australia and aims to ensure the safety of aircraft operating under the specified conditions.
Key Provisions
The Airworthiness Directive (AD/TPE331/60) issued by the Civil Aviation Safety Authority (CASA) pertains specifically to Honeywell TPE331-1, -2, -3, -5, -6 turboprop engines installed in aircraft that have been engaged in special use operations (section 1). Special use operations, as defined in the AD, involve performing multiple take-offs and landings for each engine start/shutdown cycle. The directive requires a thorough review of aircraft and engine records to determine if the installed turbine wheels are applicable (section 3). If applicable, the equivalent and total equivalent turbine wheel cycles must be calculated based on the number of aircraft take-offs and landings per engine cycle, in accordance with Honeywell Alert Service Bulletin TPE331-A72-2111 (section 3). In the absence of detailed records, a ratio of six take-offs and landings per engine major cycle is to be used for calculations (section 3). Additionally, applicable turbine wheels must be removed from service following the instructions outlined in Table 1 of the Honeywell Alert Service Bulletin TPE331-A72-2111 (section 3).
The AD imposes several obligations on the parties governed by it. Primarily, it requires the review and calculation of turbine wheel cycles based on the number of take-offs and landings per engine cycle, with applicable turbine wheels removed from service following the specified guidelines. This involves a detailed examination of aircraft and engine records, which must be conducted diligently to ensure compliance with the directive. The directive also stipulates a timeframe for compliance, with a requirement to calculate cycles within 10 hours of aircraft time in service or prior to 31 January 2003, whichever occurs first, and to remove time-limited components once this calculation is completed (section 5). These obligations are intended to mitigate the risk of uncontained turbine failure due to low cycle fatigue in engines engaged in special use operations.
Failure to comply with the requirements of this Airworthiness Directive may result in civil or criminal consequences. While the specific penalties are not detailed in the directive, non-compliance with CASA directives typically results in enforcement actions which may include fines, legal action, or other regulatory penalties. The seriousness of the directive, prompted by a recent uncontained turbine failure event, underscores the potential for significant repercussions for non-compliance. Given the safety implications highlighted in the background section, the potential penalties for not adhering to this directive could be substantial, reflecting the importance of ensuring the airworthiness of affected aircraft.