The intense heat generated when fuel and air are burned necessitates that some means of cooling be provided for all internal combustion engines. Reciprocating engines are cooled either by passing air over fins attached to the cylinders or by passing a liquid coolant through jackets that surround the cylinders. The cooling problem is made easier … Read more
While there are several important properties that satisfactory reciprocating engine oil must possess, its viscosity is most important in engine operation. The resistance of an oil to flow is known as its viscosity. Oil that flows slowly is viscous or has a high viscosity; if it flows freely, it has a low viscosity. Unfortunately, the … Read more
The primary purpose of an aircraft engine lubrication system is to reduce friction between moving parts and ensure smooth engine operation. In addition to minimizing friction, engine lubricants perform several important functions including cooling internal components, sealing gaps between parts, cushioning loads, cleaning the engine interior, and protecting metal surfaces from corrosion. Because the lubricant … Read more
Oil Tank The oil tank, constructed of welded aluminum, is serviced (filled) through a filler neck located on the tank and equipped with a spring-loaded locking cap. Inside the tank, a weighted, flexible rubber oil hose is mounted so that it is repositioned automatically to ensure oil pickup during all maneuvers. A dipstick guard is … Read more
The oil pressure branch of the engine lubrication system is pressurized by a gear-type pressure pump located in the oil pump and accessory drive housing. [Figure] The pressure pump receives engine oil at its lower (inlet) side and discharges pressurized oil to an oil filter located on the housing. From the oil filter, which is … Read more
The turbine lubrication system is representative of turbine engines using a dry-sump system. [Figure] The lubrication system is a pressure regulated, high-pressure design. It consists of the pressure, scavenge, and breather subsystems. The pressure system supplies oil to the main engine bearings and to the accessory drives. The scavenger system returns the oil to the … Read more
The dry-sump variable-pressure lubrication system uses the same basic subsystems that the regulated systems used (pressure Scavenge breather). [Figure] The main difference is that the pressure in this system is not regulated by a regulating bypass valve. Most large turbofan engine pressure systems are variable-pressure systems in which the pump outlet pressure (oil pressure) depends … Read more
In some engines, the lubrication system is the wet-sump type. There are relatively few engines using a wet-sump type of oil system. A schematic diagram of a wet-sump oil system is shown in Figure. The components of a wet-sump system are similar to those of a dry-sump system. The major difference between the two systems … Read more
Both wet and dry sump lubrication systems are used in gas turbine engines. Wet-sump engines store the lubricating oil in the engine proper, while dry-sump engines utilize an external tank mounted on the engine or somewhere in the aircraft structure near the engine, similar to reciprocating piston engines. Turbine engine’s oil systems can also be … Read more
The following component descriptions include most found in the various turbine lubrication systems. However, since engine oil systems vary somewhat according to engine model and manufacturer, not all of these components are necessarily found in any one system. Oil Tank Although the dry-sump systems use an oil tank that contains most of the oil supply, … Read more
Aviation Knowledge & Technical Study
Aero Guide provides structured aviation study materials, technical explanations, and educational resources based on FAA handbooks and other aviation references. Explore aviation fundamentals, aircraft systems, airframe structures, powerplant systems, weight and balance, and more to support your aviation learning journey.
Site Information
© 2026 Aero Guide. All rights reserved.