Engine Lubrication Flashcards
Name two items to be inspected to ensure adequate cooling of a reciprocating aircraft engine.
Cowling, cowling seals, cowl flaps, cylinder fins, cylinder baffles, and deflector system.
In what position should cowl flaps be placed for ground operation and why?
Fully OPEN because in this position they provide for the greatest amount of airflow over the engine and thus the greatest amount of cooling.
How is the combustion section of a turbine engine cooled?
Using air that has been drawn through the compressor which is routed through combustion chamber liners that provide a thin, fast-moving film of air that carries the heat away. Air is also routed to join with the burned gases aft of the burners to cool the hot gases before they enter the turbines.
What cools the bearings on a turbine engine?
Air that is bled from the compressor section of the engine and sometimes air that is drawn from outside the engine for cooling purposes is routed to the bearings. Heat is also transferred to the oil that lubricates the bearings.
What would be the effect of removing the engine baffles and seals from around a reciprocating air‑cooled aircraft engine and why?
The engine would overheat because the baffles and seals are designed to route cooling air close by and past the engine cylinders and thus draw away heat from the engine.
What are the two common types of heat exchangers used to cool engine oil on turbine engine aircraft?
Fuel oil heat exchangers and air oil heat exchangers.
What is the function and operation of an augmenter cooling system?
The function is to draw ambient air through the engine compartment for better cooling. It is accomplished with augmenter tubes or ejector tubes into which the exhaust gas is directed. This causes a low pressure and increases the flow of ambient air through augmenter and, thus, through the nacelle.
What is the difference between straight mineral oil, ashless-dispersant oil, and synthetic oil?
Straight mineral oil is blended from specifically selected petroleum based stocks. It has no additives except small amounts of pour point depressant and an antioxidant. It is used during the break-in period of a new or recently overhauled engine. Ashless dispersant oil is straight mineral oil with non-metallic, non-ash forming polymeric additives such as viscosity stabilizers. It extends operating temperature range and improves cold engine starting and lubrication during warm-up. It permits flight through a wide range of climactic changes without having to change oils. Synthetic oil is specially formulated and is used in turbine engines. It is more viscous than ashless or straight mineral oil and has a lower tendency to deposit lacquer and coke. It also resists oxidation and has superior load carrying ability. It provides long service life and prevents seal wear.
What types of oils are used for different climates?
Ashless dispersant grades of oil are recommended for aircraft engines subject to wide variations of ambient temperatures. However, below 20°F, preheating the engine and oil supply tank is normally required regardless of the type of oil used. In all cases, refer to the manufacturer’s specifications.
What are the functions of engine oil?
Engine oil acts as a cushion between metal parts and reduces friction. It cools the engine, seals, cleans, and reduces abrasive wear. Oil also prevents corrosion on the inside of the engine.
How can the technician identify and select the proper lubricants?
Aircraft oils are classified by a numbering system that is an approximation of their viscosity. There are different systems in use such as SAE and MIL-spec. Letters, such as a W, are also used to describe the oil or its characteristics. Many factors are considered when determining the proper oil for a particular engine including operating load, rotational speeds, and operating temperatures. In all cases, refer to the engine manufacturer’s information when oil type or time in service is being considered.
Name two maintenance actions that are part of servicing an aircraft engine lubrication system.
Periodic oil changes, oil filter change, inspection of oil filter contents, inspection and cleaning of oil screen(s), checking and adjustment of oil pressure relief valve, cleaning oil cooler of obstructions.
What is the reason for changing engine oil at specified intervals?
Oil in service accumulates contaminants such as gas, moisture, acids, dirt, carbon, and metallic particles which reduce the ability of the oil to protect moving parts. Replacing the oil periodically ensure the oil can do what it is designed to do.
What are two reasons for excessive oil consumption on a reciprocating engine that shows no signs of oil leakage?
Low grade oil or improper oil such as ashless-dispersant oil used in a new or overhauled engine, failing or failed crankshaft bearing(s).
