How Do Aircraft Engines Work?
The air is sucked into a turbine engine via the fan.
This passes through a compressor which spins at very high speed, raising the pressure of the air by compressing it. The squeezed air is then sprayed with fuel and an electrical spark combusts the mixture, which expands again and forces its way out of the back of the engine through the nozzle (in the case of a jet engine), providing the airplane with its thrust.
For turboprop engines the process is the same, except that the majority of expanding air forcing its way through the powerplant is harnessed to drive the propeller.
The multiple parts of the jet and turboprop engine’s components are exposed to extreme heat and pressure and require careful maintenance.
What are the Basics of Aircaft Engine Maintenance?
Here is a guide to the basic terms. Aircraft owner/operators should keep comprehensive, up-to-date logs of all aspects aircraft engine maintenance.
What is an Aircraft Overhaul?
An overhaul is where the aircraft’s engines are disassembled, its parts are inspected and measured, and certain parts are replaced (see Life Limited Components, below).
What is the Time Between Overhaul (TBO)?
The amount of time (hours) an aircraft’s engines should fly before an overhaul is performed.
Most aircraft engines come with a recommended Time Between Overhaul from the manufacturer.
How does Time Between Overhaul (TBO) affect Price/Value?
Aircraft with a shorter TBO will usually have less value than an aircraft that has undergone a major overhaul more recently.
What is a Hot Section Inspection (HSI)?
The Hot Section Inspection generally happens after a set time period (and usually at the mid-point between zero hours and the TBO limit).
The inspection focuses on engine’s components that are subjected to the extreme pressures and heat of fuel combustion.
It helps to confirm that all hot section components of the engine are in good working order, and that they will continue to produce the rated power in the engine, operating efficiently and safely until the next scheduled inspection.
Among the components subjected to an HSI are:
- the engine’s air compressors,
- combustion chambers and liners,
- the turbine wheels turned by the blast of hot air exiting nozzles on the combustion chamber.
- the blades of power and compressor turbines,
- stationary vane rings,
- turbine-shroud segments,
- temperature sensors and connections,
- compressor inlet.
What Happens if Aircraft Engine Components Fail the HSI?
Those components will need to be replaced or repaired, while other items may simply be logged for future attention if they don’t directly impact the integrity of the powerplant.
If significant deterioration isn’t found in the engine’s hot section components, an HSI tends to be a relatively low-cost major maintenance event – and the shortest, with some engines down for only a couple of days.
What are Life Limited Aircraft Engine Components?
Life Limited Components (LLCs) – come with life-limits, as set by the OEM. Those limits may be measured in hours or cycles (an aircraft take-off and landing represents one cycle). Once that limit is reached, they must be replaced.
How to Keep it Aircraft Engine Maintenance Predictable?
An aircraft engine maintenance event is one of the most expensive aspects to owning a business aircraft.
It’s possible to keep the costs predictable. Aircraft owners can enrol their aircraft on an hourly maintenance program – either with the engine manufacturer, or from a third-party program provider.
You can read more about jet engine maintenance programs here on this hub or visit our jet engine maintenance articles.