it maybe necessary to insert the defueling hose in the filler port. Normally, defueling operations are done outside the hangar and under controlled conditions. These conditions are specified in the general information and servicing volume of the applicable MIM. When it is absolutely necessary to defuel an aircraft in the hangar, the doors should be open to provide ventilation through the hangar. All shop doors leading into the hangar should be closed. No work should be done on or around the aircraft during the defueling operation. All sources of ignition should be prohibited in the area. Additional information on fueling and defueling aircraft can be found in the appropriate aircraft MIMs and the Aircraft Refueling NATOPS Manual, NAVAIR 00-80T-109. Q8. Why is wind direction an important consideration in fueling operations. Q9. Refueling crews consist of a minimum of how many people? Q10. Before beginning refueling operations, what is the first thing the refueling crew should do? Q11.  What is the advantage of pressure fueling over gravity fueling? Q12. What manuals provide detailed fueling information for a specific aircraft? OIL REPLENISHMENT Aircraft engine oils are identified by either their military specification number (such as MIL-L-23699) or a four-digit number (such as 2085). The four-digit numbering system identifies the intended use and the viscosity of the oil. The first digit designates the intended use of the oil. The last three digits indicate the viscosity. For example, in the oil number 2085, the 2xxx series is for aircraft engine lubrication, and the 085 identifies the oil as having a viscosity rating of 85. Viscosity is defined as the internal fluid resistance to flow caused by molecular attraction. NOTE: Both the Navy and the Air Force use the Saybolt scale for determining viscosity. Saybolt viscosity numbers should not be confused with Society of Automotive Engineers (SAE) numbers that you see on automotive oil containers. The synthetic oils used in most turbojet engines are referred to by their military specification number, such as MIL-L-23699. Some aircraft engines use a combination of dry and wet sump-type lubrication systems. Others are lubricated entirely with a dry sump type. Wet sump engines store the lubricating oil in the engine proper (an automobile engine is an example of a wet sump engine), while dry sump engines use an external tank mounted on or near the engine. Oil in jet engines serves the two-fold purpose of lubricating and cooling. Servicing of the engine oil system is usually a simple task. It involves checking the tank for the proper oil level and bringing the oil level up to the required amount. On aircraft that have a dry sump system, servicing may consist of pumping uncontaminated oil directly into the supply tank. However, on some aircraft the tank is located in an inaccessible compartment, and a pressure tank is required to fill the oil tank. For specific servicing instructions of the engine oil system, refer to the applicable MIM. HYDRAULIC FLUID REPLENISHMENT Aircraft hydraulic fluids are identified by their military specification number. Hydraulic fluid, MIL-H-83282, is now being used in the hydraulic systems of all naval aircraft. This fluid is also used in the shock struts, shimmy dampers, and brake systems. MIL-H-83282 hydraulic fluid is colored red. It is available in 1-quart, 1-gallon, 5-gallon, and 55-gallon containers, and 16-ounce spray cans. The spray can is normally used to spray the exposed portions of oleos (the shiny part) of actuating cylinders and struts, as required during most daily inspections of aircraft. NOTE: Hydraulic fluid MIL-H-46170 is a preservative type of hydraulic fluid used in the preservation of hydraulic systems and components. While it is red in color and considered compatible with MIL-H-83282 hydraulic fluid, it should NOT be used to service aircraft hydraulic systems. Naval aircraft hydraulic systems are serviced by checking the fluid level (on a sight gauge usually located on the side of the reservoir) and filling the system to the prescribed level. Before fluid is added to this type of reservoir, the reservoir instruction plate should always be checked for the proper filling instructions. The instruction plate is attached to either the reservoir or to the aircraft structure near the filler opening of the reservoir. The instruction plate contains the following information: Total capacity of the system 5-10