Aircraft Systems: Oil System

OIL SYSTEM

One of the most important systems in an aircraft is the oil system. In this blog. In this blog I will be talking about the importance of this system in an airplane. The main purpose of the oil system is to lubricate the engine,in other words, to create a layer between metal parts to avoid engine overheat and damage.

(CFI Notebook, n.d.)

The Cessna 172 for example, uses a wet sump oil system, which essentially means that the oil sump is located inside the engine. Oil is drawn from the sump into the engine driven oil pump. Then it goes to through a bypass valve and depending on the oil's temperature. If it cold, the valve allows the fluid to go directly to the filter, but if it is cold it first has to go through the oil cooler. Then it goes to the full flow oil filter if installed and through engine parts. The pressure relief valve allows excessive oil to return to the sump to regulate engine oil pressure. Residual oil goes back to the sump by gravity flow.

Maintenance for this system is fairly easy and can be done without a decent period of time. Pilots can check the oil level prior to the flight and the cockpit is equipped with a oil pressure and temperature gauge. Nevertheless, in flight problems with the oil system are a common cause for engine failure, specially in GA. The C172 doesn't have a oil quantity indicator, so the first sign of an issue is a drop in oil pressure. A decrease in  pressure means that less fluid is flowing through the engine parts, causing an engine overheat. Metal parts in the engine start to lose this layer of coating and friction starts to rise. The oil temperature gauge will start rising as well and once the oil level is so low, air will start entering the pressure indicator, causing a fluctuation in the gauge. Engine damage is only a matter of seconds at this point, so pilots must take immediate action as soon as they detect any issue with the oil. Once this lubricating fluid is absent, there is nothing protecting the engine parts.

References
Cessna (1976). Pilot's Operating Handbook Cessna Skyhawk. Kansas, USA.
CFI Notebook (n.d.) [Image of the wet-sump system]. Retrieved from https://www.cfinotebook.net/notebook/operation-of-aircraft-systems/lubrication

Oscar Cubas