Transport Canada has increased cycle limits on the PT6A-140, -140A and -140AG engines. These increases, which follow comprehensive parts testing and model analyses, will extend the life of low cycle fatigue (LCF) parts such as the power and compressor turbine disks and the impeller.
“We are committed to exploring and developing innovative solutions that keep our customers flying longer and at reduced operating and maintenance costs," says Nicholas Kanellias, vice president general aviation at the engine's manufacturer Pratt & Whitney Canada. "For the vast majority of PT6A-140 series operators, these extensions will push the requirement to replace LCF parts further into the future."
An engine cycle is counted every time an engine is started, flown and then shutdown. An abbreviated cycle is counted when an engine remains running between flights. The cycle limits for the PT6A-140 series engines have now been increased by up to 60 per cent for the following parts: from 12,000 cycles to 16,000 cycles for the power turbine disk, from 10,000 cycles to 16,000 cycles for the compressor turbine disk and from 19,000 cycles to 29,000 cycles for the impeller. Also, as it pertains to the power turbine disk, the number of abbreviated cycles needed to count as a full cycle has increased from two to five.
“These numbers tell a compelling story for the maintenance costs of the PT6A-140 engine series," says Kanellias. "For PT6A-140 series operators who start their engines often, these changes mean our customers will have ample time on wing to reach their second overhaul at 8,000 hours. Operators performing fewer engine starts will see their cycle impacts extended beyond the third overhaul at 12,000 hours. So while operators must always count their engine cycles, the associated maintenance, and related cost, are reduced.
“The cycle limits on the PT6A engine do not dictate the timing of an overhaul, only the need to replace a specific part," explains Kanellias. "So today's initiative increases operator value by taking an engine with enhanced attributes and elevating it to yet another level of performance and durability."