12.32.8(b) . dry sump, scavenge pump, tank; Sub Topic Syllabus Item 

A dry sump engine has a separate tank in which the oil is stored when not circulating
One or more pumps are used to scavenge the oil from the bottom of the sump where it collects at the lower part of te engine and pump it back into the separate oil tank

Scavenge Pump
– lifts the oil from the sump to the oil storage tank

Tank
– storage area for oil which is not circulating

12.32.8(a) . wet sump; 

– does not have a separate storage tank
– the oil is stored in the sump when not circulating in the engine
–

12.32.8. Briefly describe the function of the following components of an oil system:

12.32.6. Explain the effect of temperature on the lubricating qualities of oil.

High temperatures reduce the viscosity of the oil and can reduce its effectiveness as a lubricant.
Low temperatures can increase the viscosity of oil making it thick and difficult to circulate to parts of the engine.

12.32.4. Explain the term viscosity.

Viscosity = “Stickiness”
– high viscosity = thick and slow flowing oil
– low viscosity = thin and readily flowing oil

Excessively high temperatures reduce the viscousity and so the effectiveness of the oil as a lubricant

12.32.2. State the functions of an engine lubrication system.

Lubrication
– oil provides a thin film between moving surfaces
– this avoids metal to metal contact between moving parts
– avoids high friction forces and subsequent high temperatures
– avoids excessive wear on those parts

Cooling
– oil pumped under pressure goes through pipes and galleries to areas where needed
– this flow of oil is used to assist in cooling all parts of the engine
– absorbs heat generated in piston skirts, cylinder walls and main bearings
– heat is then dissipated via oil cooler

Cleaning
– the flow of oil will collect up dirt, grit and combustion products, metal flakes
– oil goes through a filter which removes solid contaminants from the oil.

12.30.8. Explain the importance of aircraft earthing during refuelling.

The aircraft and the fuelling equipment and components should be at the same electrical potential to avoid the possibility of a spark during refuelling

12.30.6. State the general rules for fuelling of aircraft, including the special precautions for the use of drum stock, and plastic containers. 

1) Check the fuel is the correct type and grade
2) Position aircraft as far away from buildings and other aircraft as possible – if too windy apply park brake
3) Ensure engine not running and ignition switches OFF
4) Adhere to the No Smoking rule
5) Keep passengers / observers clear
6) Before starting the refuel – make sure the aircraft and fuelling equipment are electrically bonded together and earthed
– make sure bonding clip attached to aircraft before fuel caps removed
7) Do not refuel if an electrical storm is in the vicinity
8) Avoid resting the full weight of the refuelling nozzle on the intake neck of the tank – can result in cracking if done regularly
9) If conditions are wet / dusty try to avoid these contaminating the fuel
10) Once refuelling is done ensure the filler caps are refitted and properly locked in place
11) Complete the FUELLING DOCUMENTATION

12.30.4. Describe the procedure to be used for a fuel drain check.

1) Use a clean glass container and drain a small quantity of fuel – 50 – 100 mls from each fuel drain valve and the strainer drain valve.
2) Fuel strainer drain is found at the lowest point in the whole fuel system
3) Any water present should appear as small globules at the bottom of the container – other impurities will be darker coloured (be aware that it is possible to get all water in the container, so be aware of the colour of the drain sample)
4) If the check is negative from each drain then empty the contents into a suitable receptacle
5) Do not tip the contents back into the aircraft tank
6) If the check is positive – carry out further checks – seek guidance from instructor or maintenance engineer

12.30.2(c) . fuel tank construction and associated limitations. 

– separate fuel tanks are located in each of the wings or in some aircraft in the fuselage. Some tanks use rubber bladders to contain the fuel, others seal the joints in a section of the airframe construction.
– incorporates an expansion space and vent above the level of the filler cap
– this enables the fuel to expand when warmed and excess pressure to be vented overboard
– filler caps are accessed from above the wing or on the fuselage as appropriate.
– overflow drain is fitted