Cessna 172C Pilot's Operating Handbook

wise to increase RPM or counter- clockwise to decrease it. For all ground operations, and for take-off, the propeller control should be full in (high RPM). After take- off, reduce throttle first, then re- duce RPM. Since a small control movement will produce a consider- able RPM change, you should set up climb and cruise RPM by screwing the knob in or out. Propeller surging (RPM variation up and down several times before engine smooths out and becomes steady) can be prevented by smooth throttle and propeller control knob operation. Do not change the throttle and propeller control settings with jerky and rapid motions. CARBURETOR AIR HEAT KNOB. The carburetor air heat knob pro- 1-1 Description portions the hot and cold air entering ing the carburetor. Pulling the knob out provides heated air for the carbu- retor, while pushing it in decreases the temperature. The knob is the double-button type, and is operated by squeezing the buttons together to unlock the control prior to moving it. STARTER HANDLE. (172 ONLY) Pulling out on the "T" shaped start- er handle engages the engine starter. It is spring loaded to return to the disengaged position when released. NOTE Don't pull out on the starter handle when the propeller is turning, as damage to the starter drive may result. IGNITION SWITCH. (172 ONLY) The ignition switch is a conven- tional, key operated, four position switch, labeled clockwise:"OFF," "R," "L," and "BOTH." IGNITION-STARTER SWITCH. (SKYHAWK & P172) The key-operated switch controls the magneto ignition system and functions as a starter switch. The switch has five positions labeled clockwise "OFF," "R," "L," "BOTH" and "START." The switch is spring- loaded in the "START" position and will return to the "BOTH" position when the key is released. 1-2 COWL FLAPS (P172) Cowl flaps, adjusted to the need, will meter enough air for the ade- quate cooling and maximum effi- ciency of the engine under varying conditions. Opening the cowl flaps, while on the ground, steps up the volume of air necessary for engine cooling. In flight, closing the cowl flaps, as required, restricts the flow of air through the engine compart- ment, thereby reducing the cooling and cowl flap drag to a minimum. When the cowl flap control is full in the cowl flaps are fully open. When the control is pulled out to its limit, the cowl flaps are closed. The cowl flap control knob is the double button type, with a friction lock, to permit intermediate settings. FUEL SYSTEM. Fuel is supplied to the engine from two aluminum tanks, one in each wing. From these tanks, fuel flows by gravity through a selector valve and a strainer to the carburetor. Refer to figure 1-2 for fuel quan- tity data. See the Servicing Diagram (figure 5-1) for a summary of fuel system servicing information. FUEL SELECTOR VALVE. A rotary type fuel selector valve is located at the aft end of the cabin floor tunnel between the front seats. The valve has four positions which are labeled "BOTH OFF," "LEFT TANK," "RIGHT TANK," and "BOTH ON." The "BOTH OFF" position seals both wing tanks off from the FUEL SYSTEM Schematic FUEL QUANTITY INDICATORS LEFT LEFT WING CHECK VALVE VENT TANK FILLER CAP FUEL QUANTITY TRANSMITTERS FUEL SCREEN FUEL TANK SUMP DRAIN PLUG TO ENGINE FUEL SELECTOR VALVE ENGINE PRIMER OIL DILUTION SWITCH (OPT) TO ENGINE OIL DILUTION SOLENOI CARBURETOR ever RIGHT RIGHT WING TANK FILLER CAP Description FUEL SCREEN FUEL TANK SUMP FUEL LINE DRAIN PLUG FUEL STRAINER FUEL STRAINER DRAIN VALVE DRAIN PLUG STRAINER DRAIN KNOB THROTTLE CODE VENT 飓 MIXTURE CONTROL KNOB FUEL TO ENGINE CYLINDERS Figure 1-1. 1-3 Description MODEL 14 TANKS USABLE FUEL NO. ALL FLIGHT FUEL QUANTITY DATA (U.S. GALLONS) UNUSABLE FUEL TOTAL ADDITIONAL USABLE FUEL FUEL CONDITIONS (LEVEL FLIGHT) |(LEVEL FLIGHT) VOLUME EACH (172) LEFT WING 1 18.0 gal. 1.0 gal. 0.5 gal. 19.5 gal. RIGHT WING 1 18.0 gal. 1.0 gal. 0.5 gal. 19.5 gal. (P172) LEFT WING I RIGHT WING .1 20.75 gal. 20.75 gal. 4.75 gal. 0.5 gal. 4.75 gal. 0.5 gal. 26.0 gal. 26.0 gal. Figure 1-2. rest of the fuel system and allows no fuel to pass beyond the selector valve. The "LEFT TANK" position allows fuel to flow from the left wing tank to the engine. The "RIGHT TANK" position permits fuel to flow from the right wing tank to the en- gine. The "BOTH ON" position pro- vides fuel flow from both tanks si- multaneously to provide maximum safety. NOTE The fuel selector valve handle indicates the setting of the valve by its position above the valve dial. FUEL QUANTITY INDICATORS. Two electrically-operated mag- netic type fuel quantity indicators are provided, each working in con- junction with an electric fuel level transmitter in its respective fuel tank. Turned on by the master switch 1-4 the indicators continue to function until the master switch is turned off. FUEL STRAINER DRAIN KNOB. The fuel strainer drain knob opens a valve on the bottom of the fuel strainer, to drain off any water and sediment that may have collected. The drain valve is spring-loaded; when the knob is pulled, the valve opens, and when the knob is released, the valve closes. About two ounces of fuel (3 to 4 seconds of drain knob operation) should be drained from the strainer before the initial flight of the day to insure against the presence of water or sediment in the fuel. ELECTRICAL SYSTEM. Electrical energy is supplied by a 12 - volt, direct - current system powered by an engine-driven gen- erator. The 12-volt storage battery is located; on the left-hand forward portion of the firewall (172); or aft of the baggage curtain (P172). Description ELECTRICAL Power Distribution Diagram SERVICE RECEPTAC LE (172) STARTER HANDLE (STANDARD 172) KEY-OPERATED STARTER SWITCH (SKYHAWK AND P172) 2 TO STALL WARNING HORN AMP STARTER SOLENOID ·TO TURN AND BANK INDICATOR (OPT) TO NAVIGATION LIGHTS + STARTER SERVICE RECEPTACLE (P172) S BATTERY BATTERY SOLENOID 10 AMP TO RADIO 3 (OPT) ΤΟ AMP TO ROTATING BEACON (OPT) 0-0 10 AMP TO PITOT HEATER AND STALL WARNING HEATER (OPT) TO FUEL GAGES AND OPTIONAL CARBURETOR AIR TEMP. GAGE TO DOME LIGHT AND (OPT) COURTESY LIGHTS TO MAP LIGHT (OPT) TO RADIO #2 (OPT) TO LANDING LIGHTS (OPT) ☛ TO CIGAR LIGHTER TO INSTRUMENT LIGHT AND COMPASS LIGHT TO RADIO #1 (OPT) B Д MASTER SWITCH GENERATOR A R 10 AMP GENERATOR WARNING LIGHT 020 AMP 10 AMP VOLTAGE REGULATOR AMMETER (OPT) 20 AMP Figure 1-3. FUSE CODE CIRCUIT BREAKER (AUTOMATIC RESETTING) CIRCUIT BREAKER SWITCH 1-5 Description FUSES. Fuses protect the majority of elec- trical circuits in the airplane. The circuits controlled by each fuse are indicated above each fuse retainer. Fuse capacity is indicated on each fuse retainer cap. Fuses are re- moved by pressing the fuse retainers inward and rotating them counter- clockwise until they disengage. The faulty fuse may then be lifted out and replaced. Spare fuses are held in a clip on the inside of the map com- partment door. The stall warning and optional turn- and-bank indicator circuits are pro- tected by an automatically resetting circuit breaker which provides in- termittent emergency operation of these devices in case of a faulty cir- cuit. The optional rotating beacon system and optional pitot and stall warning heater systems are pro- tected by separate circuit breaker switches. GENERATOR WARNING LIGHT. The red generator warning light indicates generator output. The light remains off as long as the generator functions properly. If a malfunction interrupts generator output, the light will illuminate. It also will illuminate when the battery or external power is on, before starting the engine, and whenever engine speed is insufficient to pro- duce generator output. The light does not show battery drain. 1-6 STALL WARNING INDICATOR. The stall warning indicator is an electric horn, controlled by a trans- mitter unit in the leading edge of the left wing. This system is in opera- tion whenever the master switch is turned on. The transmitter responds to changes in the airflow over the leading edge of the wing as a stall is approached. In straight-ahead and turning flight, the warning will come 5 to 10 MPH ahead of the stall. Under safe flight conditions, the only time you may hear the warning horn will be a short beep as you land. LANDING LIGHTS. A three-position, push-pull switch controls the optional landing lights. To turn one lamp on for taxiing, pull the switch out to the first stop. To turn both lamps on for landing, pull the switch out to the second stop. BRAKE SYSTEM. The hydraulic brakes on the main wheels are conventionally operated by applying toe pressure to either the pilot's or copilot's rudder pedals. To set the parking brake, apply toe pressure to the pedals, pull out on the parking brake knob, then release toe pressure. To release the park- ing brake, push the knob in, then apply and release toe pressure. FIRMLY PRESS ON BRAKE PEDALS. 1-7 Brake Cylinder TO SET YOUR PARKING BRAKE PULL OUT ON PARKING BRAKE KNOB. RELEASE THE FOOT PRESSURE FROM THE BRAKE PEDALS BEFORE RELEASING PARKING BRAKE KNOB. -Brake Pedala NOTE Do not pull out on the knob with a hard pull. Merely pull the knob out as far as it will go with an average amount of pressure. Locking Lever is pulled up NOTE The parking brake knob is spring-loaded and will return to its original po- sition when the hand pres- sure is released. Your Brakes are now set. PUSH PARKING BRAKE KNOB ALL THE WAY IN. Brake Cylinder TO RELEASE YOUR PARKING BRAKE APPLY FAIRLY HEAVY FOOT PRESSURE TO BRAKE PEDALS. C RELEASE THE FOOT PRESSURE FROM THE BRAKE PEDALS. Cessna The Locking Lever will anap down in this operation. Nor- mally, you can hear a click when the levers snap down. Your Brakes are now released. Figure 1-4. Description