Consistent, quality aircraft engine maintenance is vital to the overall health and longevity of your turboprop. Every 1800 flight hours, that engine maintenance includes a hot section inspection.
What is a Hot Section Inspection?
A hot section inspection (HSI) involves the thorough and detailed inspection of an engine’s vital parts, including the turbine blades, combustion chamber, vane rings, compressor turbine disk, and CT shroud segments. For King Airs with PT6 engines, specifically, hot section inspections are typically performed every 1800 flight hours, though some are performed at different intervals depending on the engine model installed..
How does a maintenance team perform a hot section inspection?
A hot section inspection can be approached in a few different ways, depending on whether or not the inspection is being combined with other maintenance. In most instances, a hot section inspection can be performed on-wing, meaning the entire engine doesn’t need to be pulled off the aircraft. This is a completely different process for the TPE-331 engines versus the PT-6 engines, for example. With the TPE331s, the engine must be pulled off wing in order to perform a hot section inspection. The main reason for this difference is that a PT6 is a reverse flow engine, meaning the engine’s hot section is located on the forward portion of the engine as compared to the aft portion of the engine on a TPE331.
In order to perform a King Air hot section inspection, the maintenance team will split the engine at the c-flange and the power section will be removed from the rest of the engine, with the harness and probes still attached. With the power turbine, combustion chamber, exhaust duct, and compression turbine exposed, the maintenance team will perform the inspection. If everything passes inspection, the maintenance team will reinstall the power section at the c-flange and move forward with reassembly. That typically isn’t the case, however.
One of the main reasons why a hot section inspection is so important is because those engine components should be inspected and maintained to avoid catastrophic engine failure. If the maintenance team inspects those components and there is cracking, for example, that is their opportunity to remedy the issue immediately.
A knowledgeable and detailed maintenance team will understand that some cracking is acceptable, but that there are on-wing(in service) and on-bench criteria that vary per engine. Prior to a hot section event, fuel nozzle spray and flow check are typically performed every 400 hours leading up to the hot section inspection at 1800 hours. The fuel nozzles, which are the heart of the engine, should visually have a clear pattern with no streaking coming from the nozzle tips. Alongside the fuel nozzle inspection and prior to the hot section inspection, a borescope inspection should also be performed at the same 400 hour interval.
For the borescope inspection, a borescope is inserted into the engine which allows the maintenance team to internally inspect the components. If cracking is visible with the borescope, the engine may be serviceable. However, once the hot section inspection is performed and the engine is split at the c-flange, serviceable criteria will have changed and the limitations will have narrowed. Again, all of these efforts are an event to prevent catastrophic failure. If issues are caught early enough and components are replaced, a catastrophic event is more easily avoided.
Combining services with hot section inspections
Certain services can be combined with hot section inspections in an effort to save on labor costs. This includes: fuel nozzle inspections; componentry inspections such as engine fluid lines, oil lines, and flexible fluid lines; as well as phased inspections. For example, if an aircraft is coming due for a Phase 1 and Phase 2 inspection within a 40 to 50 hour flight period, your maintenance team should work with you to combine that inspection with your hot section inspection so your aircraft only experiences downtime once.
Contact Winner Aviation for your hot section inspection
At Winner Aviation, our maintenance team is well versed in King Air hot section inspections and what is needed to combine those inspections with other services to save you money and downtime. We’re here to help. Contact us today to request a quote or to speak with a member of our maintenance team.