How Does the Aircraft Engine Oil System Work?

The aircraft engine is a powerful apparatus, serving to combust fuel-and-air mixtures to create the propulsion and thrust necessary for sustained heavier-than-air flight. As engines are in constant operation during a flight, the assembly is faced with intensive pressure, extreme heat, and more. With all of these stressors, engines can quickly begin to fall apart if ample protection is not in place. To deter wear and tear, as well as to promote increased efficiency, aircraft utilize an engine oil system that performs numerous crucial roles. For a standard aircraft engine, the oil system serves to lubricate moving parts, reduce friction through cooling, remove heat from operating cylinders, create seals between cylinder walls and pistons, and carry away contaminants that have built up in the assembly. In this blog, we will discuss aircraft engine oil systems in more detail, allowing you to better understand their types and functionality.

Depending on the type of aircraft in question, the oil system may vary in its design and capabilities. For example, reciprocating engines often feature either a wet or dry sump. With a wet sump, the engine oil is situated within a sump that serves as a standard part of the engine assembly. On the other hand, dry-sump systems are those where the oil is contained within a tank that is separate from the engine. As such, oil will need to be pumped into the engine for use.

With a wet-sump system, the oil pump is one of the most crucial elements, acting to transfer oil from the sump and into the engine. After passing through the engine for cooling, lubrication, and build-up removal, the oil is then returned to the sump. If an increased amount of lubrication is required, a reciprocating engine may utilize its rotating crankshaft to splash oil onto sections of the engine assembly.

Dry-sump systems also heavily rely on their oil pump for supplying oil under pressure, and their source is a separate oil tank that is placed near the engine. Similar to the wet-sump system, oil is routed throughout the entire engine before being returned to the source, albeit with scavenge pumps. With a dry-sump’s ability to supply a large amount of oil to the engine with ease, it can perform much more optimally for a large reciprocating engine when compared to the wet-sump option.

With either type of system, performance will often come down to how optimally oil can be pressurized for use. Using the oil pressure gauge, pilots can quickly determine oil pressure in terms of pounds per square inch (psi). The green section of the gauge is the normal operating range where pressure should remain, while the red sections are the minimum and maximum pressure values. During the engine starting process, the pilot should be able to receive a direct reading.

Oil temperatures are also important to consistently monitor, and the temperature gauge is fairly similar to the pressure gauge with green and red sections to indicate operating ranges. Oil temperature changes are much slower than pressure changes, thus a pilot will need to remain cognizant of readings throughout a flight to ensure that everything is performing well. Too hot of oil may indicate a clogged oil line or a low oil quantity, while low temperatures point toward improper oil viscosity.

If you need to measure the oil quantity of your oil system while conducting ground operations, you may open a panel in the engine cowling to access the oil filler cap and insert a dipstick to get a reading. If oil levels are below recommended values, then you must add oil to the system before conducting a flight. To determine the right type of oil and quantity to add, refer to placards that are placed near the access panel.

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• Posted on May 6, 2022
• charles lec
• aviation

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