The Pratt & Whitney PT6 engine has been in use since 1961 and has since logged more than 380 million flight hours, the equivalent of about 250,000 round-trips to the moon. The most advanced PT6A engine family includes three power levels, “Small”, “Medium”, and “Large” that all have the advantage of turbine cooling, aerodynamic design, and advanced technologies in materials. Keeping these engines running efficiently and safely wouldn’t be possible without a periodic Hot Section Inspection.
What is a Hot Section Inspection?
With a PT6A, a Hot Section Inspection (HSI) is not a full overhaul and doesn’t necessarily need to be costly. The objective of an HSI to certify that the hot section elements of your engine are able to generate acceptable power for efficient and safe performance until it is time for the next HSI or TBO.
When an HSI is done, the hot section components of the engine are inspected. This includes the turbine blades, vane rings, CT shroud segments, temperature sensing system, and compressor inlet. If necessary, those components will be repaired or replaced. Other items may simply be identified but not addressed if they do not affect the integrity of the engine. For example, cracks in non-rotating parts may be acceptable for continuing operation as well as minimal erosion and corrosion, or ceramic coating loss.
An HSI can turn costly if major components in the hot section have begun to deteriorate. If such things as turbine blades, vane rings, combustion liners and other costly components need to be replaced, the HSI can become expensive. Regardless, these are items that are necessary to ensure the safe and efficient operation of your engine going forward.
When to Schedule a Hot Section Inspection
A Hot Section Inspection should be performed on your PT6A at the halfway point to the Time Before Overhaul (TBO). This is after 1,800 hours for “Small” and “Medium” engines and after 2,000 hours for the “Large” PT6A. While this seems like a simple enough thing to tick off on your schedule, there are exceptions. HSIs should also be performed on an unscheduled basis on occasion. This needs to take place if there are certain performance degradation or overtemp issues with your engine.
When you schedule your Hot Section Inspection, an engine performance check should be performed both before and after the HSI. Doing this will allow the technician to determine the status of the hot section components and set performance parameters for the engine. The PT6A is an engine with a proven history of reliability. Adding a Hot Section Inspection to your maintenance schedule will ensure that your engine continues to provide you with years of efficient and safe operation.