Pilot's Operating Handbook

which features very efficient filtering action with negligible re- striction to carburetor inlet flow. Also optional is a full flow oil filter, with easily replaceable cartridges. The standard propeller on the PA-25-235 is a McCauley one-piece metal design. Also available for the PA-25-260 is either a Hartzell HC-C2YK-1/8477 -0 or a McCauley B2D34C16/ 84HF-0 constant speed propeller. FUSELAGE AND WINGS The fuselage frame is constructed of steel tubes, welded to form a rigid structure. Highly stressed members are made of 4130 chrome-moly steel, others are of 1025 steel. 761 586 770518 i W SECTION II PAWNEE D Repairs to the fuselage can be made in accordance with the requirements of Aviation Circular 43.13-1. Repair facilities for this type of construction are commonly available. The fuselage structure is treated as follows to eliminate corrosion. The interior of the lower tubing is coated with Lionoil to prevent internal corrosion. The longerons and di- agonal tubes are completely sprayed with zinc chromate primer followed by a coating of Rexton Activated Copon paint. A paste mixture composed of Permalite and polyester resin is applied at various points on the structure to eliminate dust pockets. Dope sealer is applied to the frame at points where fabric at- taches. The wing framework consists of riveted aluminum ribs mounted on extruded aluminum spars with tubular drag and compression struts and high strength stainless steel drag wires. Aluminum sheet is used to form the leading edge and the false spars. An ash wing-tip bow provides a light tough member which can withstand considerable wing tip shock with- out failing. The wings are attached to the fuselage at fittings on the lower longerons, and by means of compression struts which bolt to upper fuselage members and wing spar fittings. The rear struts may be adjusted by means of a threaded attachment fitting at the outboard end of the struts. This adjustment is used to set the rigging of the wings. LANDING GEAR The Pawnee "D" landing gear employs as standard equipment automotive type shock units combined with shock cord rings. Optional air-oil type shock absorbers are also avialable. (Consult Section IV for shock absorber maintenance.) The only maintenance normally required is lubrication of the hinge bolts and each end of the shock struts according to the lubrication chart. The steel hinge bolt bushings should be in- spected and replaced if worn. 5 761 586 770518 ☑ PAWNEE D SECTION II The Scott 8" steerable, full-swivel tail wheel is standard equipment on the Pawnee. This unit is combined with steel leaf springs which are easily replaced if needed. The main wheel assemblies are Cleveland Products 40-84A with Cleveland 30-41 Disc Brake Assemblies. The tires are 8:00 x 6 four ply rating. Tires should be inflated to 25 psi to prevent slippage and to produce even wear. W CONTROL SYSTEM The fin, rudder, stabilizers and elevator are all constructed of tubular steel with steel channel ribs. The control surface hinges have bronze bushing inserts and should be oiled accord- ing to lubrication chart. The elevators and the rudder are de- signed with an aerodynamic balance to increase stability and lighten control forces. Double stainless steel tie rods and fittings brace the stabilizers to the fin and fuselage. The tail brace wires should not be used for lifting or ground handling of the air- plane. _ EMPENNAGE Conventional flight and engine controls are provided in the Pawnee. The flap lever has three positions, full up, half, or full down. The flaps are provided for an increased angle of descent only and should not be used for take-off or climb. The elevator trim control is located on the left side of the cockpit and consists of a two-spring system with an irrever- sible geared crank mechanism. This system normally requires very little maintenance except for inspection and lubrication according to lubrication chart. 761 586 740111 6 ய 7 SECTION II PAWNEE D FUEL SYSTEM A 38.5 gallon fuel supply (36 gallons usable) is carried in two aluminum fuel tanks, one in each wing. An electric fuel quantity gauge, a fuel pressure gauge and a low fuel warning light are mounted on top of the center of the instrument panel. The low fuel warning illuminates when approximately 7 gallons of fuel is left on board. The fuel shut-off valve is controlled by a "T" handle on the right side of the cockpit. In addition to the engine-driven fuel pump, there are two electric fuel pumps connected in parallel and activated by a single ON-OFF switch mounted on the sub-panel on the lower right of the instrument panel. Circuit breakers for the electric fuel pumps and fuel quantity indicator are also mounted on this sub-panel. To facilitate starting, an engine primer pump on the left side of the instrument panel may be used to manually pump fuel directly into the engine cylinders. To prevent engine malfunction, the primer pump should be locked in at all times except when in use. Both fuel tanks feed simultaneously into a header tank which serves to maintain a constant flow of fuel to the engine. The header tank is equipped with a quick-drain and a float valve connected to the vent line. The header tank drain and vent line drain are located aft of the wing on the underside of the fuselage. The fuel filter drain is also located on the underside of the fuselage but aft of the firewall. Each fuel tank has a drain located on the underside of the wing. Before each flight the quick-drain valves should be opened for a few seconds to remove water or sediment from the fuel system. One way check valves are used in the vent line to prevent excess fuel overflow during taxi turns or uncoordinated flight. These check valves have two pressure release holes which bypass the check valves and will allow slight overflow during thermal expansion of a full tank. An idle cut-off is incorporated in the mixture control - the engine should be stopped with the idle cut-off. NOTE To insure lateral stability, fuel tanks must not be filled asymmetrically. 761 586 770518 810320 761 586 CARBURETOR THROTTLE MIXTURE ENGINE FUEL PUMP TO PRIMER NOZZLES ELECTRIC PUMPS S/N 25-7405573 thru 25-7956006 ELECTRIC FUEL QUANTITY GAUGE FUEL PRESSURE GAUGE ☑☑ FUEL FILTER FILLER ENGINE PRIMER PUMP FILTER DRAIN SHUT-OFF VALVE CHECK VALVE PAWNEE D FUEL PRESSURE TRANSDUCER S/M 25-7956007 and up ELECTRIC FUEL PRESSURE GAUGE QUANTITY SENDER RIGHT TANK TANK DRAIN HEADER TANK ✓ HEADER TANK DRAIN FLOAT VALVE VENT LINE VENT LINE DRAIN CHECK VENT LEFT TANK 8 CHECK VALVE FUEL SYSTEM SECTION 11 W SECTION II PAWNEE D - ELECTRICAL SYSTEM A 12-volt, 35-ampere hour battery, voltage regulator, ammeter, starter solenoid, alternator, two electric fuel pumps, stall warning light, fuel gauge and warning light, switches, circuit protectors and related wiring are all standard equipment on the Pawnee. The battery is mounted in the lower right side of the nose section, aft of the engine fire wall. Access to the battery may be gained through a plate secured to the fuselage with quarter turn screw-type fasteners. The master solenoid and an energizing diode are attached to the battery box. The diode excites a circuit permitting a completely dead battery to be charged after the engine is cranked manually. The voltage regulator is located under the cockpit floor. All electrical switches, the ammeter, and the circuit breakers are located on the right side of the instrument panel. The circuit breakers automatically break the electrical circuits should an overload occur. When resetting an open circuit breaker, allow sufficient time for the breaker to cool before resetting the circuit. Position lights, anti-collision lights, landing light, and instrument lights are available as optional equipment. FINISH The finish of the Pawnee consists of fire-resistant butyrate plastic material on the fabric surfaces and Rexton enamel on metal surfaces. The butyrate finish must not be covered over with any incompatible material. The use of different materials from those originally applied will damage the finish. CABIN FEATURES The standard instrument group includes the following: altimeter, airspeed, compass, oil temperature and pressure gauge, fuel quantity and pressure gauge, and a tachometer. The seat is adjustable fore and aft and up and down. The angle of the seat back is not adjustable. ' ! 761 586 740111