PT6 manuals require that a Hot Section Inspection (HSI) is carried out on engines halfway to the basic Time Between Overhaul (TBO) the timescales for Hot Section Inspections are stipulated within the specific engine Service Bulletin.
Standard procedure is that if any over-temping or performance loss is noticed by the pilot or aircraft engineers, which cannot be rectified by standard Maintenance Manual (MM) troubleshooting, an HSI is performed. This is where an engineer will perform a visual inspection to determine the condition of the Hot Section parts. Once the inspection has been completed and the engine re-assembled, a performance test is carried out to ensure the operating levels of the engine are acceptable.
Before the HSI is carried out, a base-line performance run should be performed, but only if possible or practical. A borescope/visual inspection of the cold section should be done to ensure that there is no damage within the Compressor. However, if damage within the Compressor is verified and is outside MM criteria and cannot be rectified, then an HSI is not recommended, as the engine will have to be removed from service. The HSI itself begins with the removal of the power section of the engine. The CT Disk, Blade Assembly, Combustion Chamber and Vane Ring Assembly are then removed. The engineer will be looking for cracks, distortion, burning, fretting wear, hot spots and any blockages to the cooling holes. If the parts need repairing or replacing, the engineer will do this. This process can be performed on wing with the smaller turboprop engines such as the PT6, making it a perfect job for the Field Service Teams or Mobile Repair Teams. A major cause of Hot Section life reduction is poorly performing Fuel Nozzles, which are designed to produce a cone of fuel into the chamber. However, as they become clogged from use and damage, the cone shape of the fuel spray becomes less uniform and can further damage components. Therefore the Hot Section Inspection will also include the Fuel Nozzles, to ensure that they are operating as they should to ensure safety, minimal loss of performance and reduce TBO costs. If there are non-rotating parts that show evidence of wear, these are not replaced or repaired unless the condition shows this as being essential. Once these parts have been inspected, the engine can be reassembled and the engine test performed again.
Euravia can carry out these Hot Section Inspections for you, either at our facility or on site by our Field Service and Mobile Repair Teams (MRT), if required, to avoid unnecessary AOG downtime. Our teams are fully OEM trained and use OEM parts. We also offer the option of a Fuel Nozzle service and replacement that enjoys industry-leading turntime, keeping your business operational.