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Chapter 11. Safety, Ground Operations, & Servicing Hand Cranking Engines If the aircraft has no self-starter, the engine must be started by turning the propeller by hand (hand propping the propeller). The person who is turning the propeller calls: “Fuel on, switch off, throttle closed, brakes on." The person operating the engine will check these items and repeat the phrase. The switch and throttle must not be touched again until the person swinging the prop calls “contact." The operator will repeat “contact" and then turn on the switch. Never turn on the switch and then call “contact." A few simple precautions will help to avoid accidents when hand propping the engine. While touching a propeller, always assume that the ignition is on. The switches which control the magnetos operate on the principle of short-circuiting the current to turn the ignition off. If the switch is faulty, it can be in the “off" position and still permit current to flow in the magneto primary circuit. This condition could allow the engine to start when the switch is off. Be sure the ground is firm. Slippery grass, mud, grease, or loose gravel can lead to a fall into or under the propeller. Never allow any portion of your body to get in the way of the propeller. This applies even though the engine is not being cranked. Stand close enough to the propeller to be able to step away as it is pulled down. Stepping away after cranking is a safeguard in case the brakes fail. Do not stand in a position that requires leaning toward the propeller to reach it. This throws the body off balance and could cause you to fall into the blades when the engine starts. In swinging the prop, always move the blade downward by pushing with the palms of the hands. Do not grip the blade with the fingers curled over the edge, since “kickback" may break them or draw your body in the blade path. Excessive throttle opening after the engine has fired is the principal cause of backfiring during starting. Gradual opening of the throttle, while the engine is cold, will reduce the potential for backfiring. Slow, smooth movement of the throttle will assure correct engine operation. Avoid overpriming the engine before it is turned over by the starter. This can result in fires, scored or scuffed cylinders and pistons, and, in some cases, engine failures due to hydraulic lock. If the engine is inadvertently flooded or overprimed, turn the ignition switch off and move the throttle to the “full open" position. To rid the engine of the excess fuel, turn it over by hand or by the starter. If excessive force is needed to turn over the engine, stop immediately. Do not force rotation of the engine. If in doubt, remove the lower cylinder spark plugs. Immediately after the engine starts, check the oil pressure indicator. If oil pressure does not show within 30 seconds, stop the engine and determine the trouble. If oil pressure is indicated, adjust the throttle to the aircraft manufacturer’s specified rpm for engine warmup. Warm-up rpm will usually be in the 1,000 to 1,300 rpm range. Most aircraft reciprocating engines are air cooled and depend on the forward speed of the aircraft to maintain proper cooling. Therefore, particular care is necessary when operating these engines on the ground. During all ground running, operate the engine with the propeller in full low pitch and headed into the wind with the cowling installed to provide the best degree of engine cooling. Closely monitor the engine instruments at all times. Do not close the cowl flaps for engine warm-up; they should be in the open position while operating on the ground. When warming up the engine, ensure that personnel, ground equipment that may be damaged, or other aircraft are not in the propeller wash. |
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