Removing an aircraft’s engine can be one of the most difficult and complicated procedures in aircraft maintenance. Given the enormous variety in aircraft and engine designs, there is no single list of instructions that can be provided as a guideline, as every airframe and every engine layout will inevitably have a different checklist that must be followed. There are, however, universal requirements that every engine will have that must be fulfilled, such as disconnecting and reconnecting the electrical, hydraulic, and fuel supply lines, the intake and exhaust path components, the engine controls, and the engine mounting connections to the airframe. One should always refer to the engine manufacturer’s instructions when performing any type of engine removal or installation.
Engines are removed for a number of reasons, the first and most common being that the engine or a component within it has exceeded its operational lifespan. Lifespan depends on variables like operational use, quality of manufacture or overhaul, the degree of maintenance performed, and the types of operations being carried out by the aircraft. The manufacturer sets engine removal times based off of these factors. Based on service experience, it is possible to establish a maximum expected time before overhaul (TBO) or span of time within which an engine needs to be overhauled. Regardless of condition, an engine must be removed when it has accumulated the recommended maximum allowable time since its last overhaul. Regardless of its condition, an engine must be removed when it has accumulated the recommended maximum allowable time since its last overhaul.
Another common reason for removal is sudden stoppage. Sudden stoppage is a rapid and complete stoppage of the engine’s functions, and can be caused by engine seizure, or by a propeller blade striking an object in such a way that the revolutions per minute drops to zero in less than one complete revolution of the propeller. Sudden stoppage occurs under conditions like complete and rapid collapse of the landing gear, nosing over of the aircraft, or crash landing. A sudden stoppage can cause internal damage to components like the propeller gear teeth, the gear train, the crankshaft counterweights, and the propeller bearings. When sudden stoppage occurs, disassembly and replacement is almost always required.
Another reason for removal and disassembly is when metal particles in the engine oil screens or magnetic chip detectors are found. This can mean that there is an internal failure in the engine, and something is falling apart. However, carbon that breaks loose in the interior of the engine can come in rock-like pieces that resemble metal, so to check against this, simply place any suspect particles near a magnet. If they are affected, it means that they are made of metal and something is broken inside the engine.
Other common reasons for engine removal include excessive engine vibration (especially in turbines), backfiring and misfiring, and overall low power output..
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