There are NO STEP markings on the leading and trailing edges of the horizontal stabilizer. These markings form a boundary around the surface on which maintenance personnel must not step or kneel upon unless they cover it with an approved nonabrasive surface mat. The mat distributes the load over a greater area. Stepping or kneeling on the unprotected horizontal stabilizer causes localized stressed areas that could result in structural damage to the surface. CAUTION Do not step or kneel on the overwing fair- ings. There are four NO STEP areas on the fuselage. These areas are aft center body, the upper speed brake, the area directly aft of overwing fairings, and the area directly behind the canopy. The NO STEP markings on the upper speed brake, aft center body, and the area directly aft of the over-wing fairing form a boundary around each of these surfaces on which maintenance personnel should not step. Maintenance Platform Placement The placement of maintenance platforms about an aircraft is shown in figure 5-3. Use the B-4 and B-5A adjustable maintenance platforms to gain access to the top of the aircraft. Then use aircraft walkways to move to the maintenance area. NOTE: The B-1 stand may be used as an alternate for the B-5A stand. FUEL REPLENISHMENT 5-6 Q5. Smoking and naked lights are not permitted within how many feet of a fueling operation? Q6. What type tools must be used when work is being performed on a system or unit that is designed for storing or handling combustible liquids. Q7. What are the four NO STEP areas on the fuselage? Aviation fuel is a highly volatile liquid that gives off a vapor. The vapor can be ignited by static sparks from tools, hot exhaust pipes, lighted cigarettes, and electrical devices. Thus, you must follow all fire precautions during the fueling process. When an aircraft is to be fueled by a truck, do not locate the aircraft near possible sources of ignition, such as grinding, drilling, or welding operations. When possible, refueling an aircraft from a truck should be carried out 50 feet from any other aircraft or structure and 75 feet from any operating radar set. You should consider wind direction so fuel vapors will not be carried toward a source of ignition. The tank truck should be driven to a point as far from the aircraft as the length of hose permits, but never within 10 feet of the aircraft, and preferably to the windward (upwind) side of the aircraft. The truck must be parked parallel to or heading away from the wing, or in such a position that it can be driven away quickly in case there is a fire. As soon as the fueling operation has been completed, the truck should be driven away from the vicinity of the aircraft. Refueling crews consist of a minimum of three people. One person stands with the fire-fighting equipment. A second person stays with the truck. The third person handles the fuel hose at the aircraft and fills the tanks. A member of the refueling crew makes sure that both the aircraft and truck are properly grounded. This prevents sparks from static electricity. Before starting fueling operations, the plane captain should check to see that all radio equipment and unnecessary electrical switches are turned off. Unless it is necessary to operate equipment involved with refueling, the crew should not connect outside electrical power to the aircraft. Before beginning refueling, the refueling crew should identify the aviation fuel. The type of fuel contained in the tank of a fuel truck is displayed across the side of each tank in 6-inch-high red lettering superimposed on 8-inch-high white reflective tape. As a plane captain or trainee who services an aircraft, you must know the various grades of fuel and the fuel requirements of the aircraft. This knowledge ensures that you will always use the correct fuel. Several systems are used to refuel naval aircraft. Some are refueled by the gravity system. Other aircraft may be refueled by either the gravity or pressure fueling system. Still other aircraft are fueled from a single point by the pressure fueling system. Gravity Fueling The hookup used for gravity fueling is shown in figure 5-4. The nozzle is grounded and then inserted into the cell filler neck. The tank is filled to the bottom of the filler port neck. The nozzle is always grounded