AD/PT6T/10 - Compressor Bleed Off Valve

Overview

The Civil Aviation Regulations 1998, administered by the Civil Aviation Safety Authority, encompass a range of safety directives aimed at ensuring the integrity and safety of aviation components. One such directive, AD/PT6T/10, pertains specifically to Pratt and Whitney Canada's PT6T series turbine engines, targeting the compressor bleed off valve. The directive was enacted to address a potential safety issue where the movement in the valve guide shaft pin might lead to a fracture of the cotter pin, subsequently causing jamming of the bleed off valve. Such a malfunction could result in a reduction of required engine power or an engine surge event, posing significant safety risks. The directive mandates inspections of the bleed off valves and stipulates actions based on the supplier code, with the overarching policy objective being to prevent these potential failures and maintain the highest safety standards in civil aviation. Compliance with this directive is critical, requiring inspections to be conducted either within 100 hours of the engine's time in service or before 30 May 1997, whichever comes first.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 106, mandates the applicability of Airworthiness Directive AD/PT6T/10, which concerns Pratt and Whitney Canada (PWC) PT6T series turbine engines, focusing on the compressor bleed off valve. This regulation applies to all Pratt and Whitney Canada PT6T engines identified by the serial numbers outlined in PWC Service Bulletin 5394. The directive requires inspection of the bleed off valve to ascertain the supplier code. If the supplier code is “8070”, the bleed off valve must be inspected in accordance with PWC SB 5394 to prevent potential malfunctions that could lead to a reduction in engine power or an engine surge event. Conversely, if the supplier code is not “8070” or if the bleed off valve has been re-identified to “RE71”, no further action is required. This directive is effective as of 27 March 1997, and compliance must be achieved unless the required inspection has already been performed; it must be completed within 100 hours of time in service or before 30 May 1997, whichever comes first. This regulation thus extends to all relevant aircraft operators and maintenance personnel responsible for ensuring the airworthiness of PT6T engines in compliance with Australian civil aviation safety standards.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39, Section 106, details the Civil Aviation Safety Authority's (CASA) Schedule of Airworthiness Directives. This section includes AD/PT6T/10 which concerns Pratt and Whitney Canada (PWC) PT6T series turbine engines. The directive mandates that certain compressor bleed off valves be inspected to prevent malfunctions that could result in a reduction of engine power or an engine surge event (AD/PT6T/10). The directive applies to all PT6T engines, as detailed by serial number in PWC Service Bulletin 5394. According to the directive, operators must inspect the bleed off valve to determine the supplier code. If the supplier code is "8070", the bleed off valve must be inspected in accordance with PWC Service Bulletin 5394 (AD/PT6T/10, clause 1). If the supplier code is not "8070" or if the bleed off valve has been re-identified to "RE71", no further action is required (AD/PT6T/10, clause 2). This directive references Transport Canada Airworthiness Directive CF-96-24. Compliance with AD/PT6T/10 is mandatory and was effective from 27 March 1997. Operators must ensure the inspection is completed unless it has already been performed. The inspection must occur within 100 hours of the engine being in service or before 30 May 1997, whichever comes first (AD/PT6T/10, compliance clause). Failure to comply with this directive may result in the engine's inability to deliver the required power or an engine surge event, potentially leading to safety hazards. The directive was issued to address the risk of movement in the valve guide shaft pin, which can cause the cotter pin to fracture and the valve to jam. Such failures could result in significant operational issues, including the loss of required engine power or an engine surge. Adhering to the specified inspection and maintenance procedures is crucial to ensuring the safe and efficient operation of the PT6T engines.