maintenance instruction manual (MIM) contains illustrations of and instructions for the pressure fueling system. The pressure nozzle shown in figure 5-5 is permanently attached to the fuel hose. The pressure nozzle has a ground wire, which is used to drain off any static electricity that has built up in the nozzle. Once the nozzle is attached to the aircraft, however, it acts as a ground. When the pressure nozzle is connected to the aircraft, it opens a spring-loaded valve within the inlet to the fuel tanks. Aircraft that use this system have automatic equipment for shutting off the fuel flow when the tanks are full. Because the controls differ from one aircraft to another, you should always check the applicable MIM before pressure fueling an aircraft. The general procedures for pressure fueling are as follows: 1. Remove the pressure-fueling receptacle safety cap by turning it counterclockwise. Pull the pressure-fueling nozzle dust cover up and to one side of the outer shell. 2. Ground the nozzle by inserting the grounding plug into its receptacle on the aircraft. 3. Visually inspect aircraft adapter for any damage or significant wear. (A worn or broken adapter will allow the poppet valve to open and spray or spill fuel.) 4. Lift the nozzle by its handles into position. Engage the lower slot over the lower lug on the fueling receptacle. Tip the nozzle so that the upper slots engage the upper lugs. Press the nozzle in firmly so that all three nozzle lock keys are depressed. Lock the nozzle by rotating the lifting handles clockwise. 5. Set the refueling panel switches in the proper position, and apply electrical power to the aircraft. 6. Position the vent monitors, as necessary, according to the applicable MIM. NOTE: The vent monitors are assigned to the various fuel system vents to ensure that the aircraft’s fuel cells are venting properly. If the cells are not vented properly, there is the possibility that the cell will rupture and cause major structural damage. 7.   When the nozzle is locked in place, the opening handle is free to turn when fueling is started. Turn the handle to the FULL OPEN position to start fueling. Rotating the opening handle more than 180° opens the poppet valve in the nozzle and locks it in the OPEN position. Position the appropriate switch on the fuel panel to the FUEL position. The fuel should shut off automatically when the ceils are full. CAUTION During pressure fueling, the fuel system should be inspected carefully for leakage. If any leaks are apparent, fueling should be stopped and corrective action taken. A fuel leak may cause injury or death to personnel. 8.   When the fueling operation is complete, remove the pressure nozzle by rotating the lifting handles counterclockwise until the nozzle is unlocked from the fueling receptacle. Pull the dust cover up over the nozzle face immediately. Then replace the safety cap on the aircraft receptacle. You must take every safety precaution to make sure that no dirt or foreign matter enters the nozzle. The nozzle nose should be completely clean before it is connected to the aircraft. The dust cover must always be kept on the nozzle except when actually fueling an aircraft. The pressure fueling nozzle can be damaged by careless handling. Do not drop the nozzle or allow it to swing heavily against structures or equipment during handling. Never drag the nozzle on the deck. The operating action of the nozzle should never be forced. If the unit does not couple freely or open or close readily, locate and correct the misalignment or mechanical jam. Defueling Defueling may be necessary for many reasons, some of which are fuel cell repairs, removal of external fuel tanks, failure of fuel system components, and changing fuel loads. Aircraft that use pressure fueling are normally defueled from the pressure fueling adapter. This allows the entire system to be defueled from a single point. Some older aircraft have one or more defueling valves. Some residual fuel will often be left in the bottom of the fuel cell following defueling. Usually, residual fuel can be emptied or drained through the fuel cell water drain valves. A special adapter and appropriate container are used to catch the fuel. When external fuel tanks are defueled, 5-9