The pilot should be familiar with the manufacturer’s recommended starting procedures for the airplane being flown. This information can be found in the Airplane Flight Manual or Pilot’s Operating Handbook, or other sources. There are not only different procedures applicable to starting engines equipped with conventional carburetors and those equipped with fuel injection systems, but also between different systems of either carburetion or fuel injection. The pilot should always ascertain that no one is near the propeller, call “clear prop,” and wait for a possible response before engaging the propeller. Continuous cranking beyond 30 seconds’ duration may damage the starter. In addition, the starter motor should be allowed to cool at least l to 2 minutes between cranking periods. If the engine refuses to start under normal circumstances after a reasonable number of attempts, the possibility of problems with ignition or fuel flow should be investigated.
As soon as the engine starts, check for unintentional movement and set power to the recommended warmup RPM. The oil pressure should then be checked to determine that the oil system is functioning properly. If the gauge does not indicate oil pressure within 30 seconds, the engine should be stopped and a check should be made to determine what is causing the lack of oil pressure. If oil is not circulating properly, the engine can be seriously damaged in a short time. During cold weather there will be a much slower response in oil pressure indications than during warmer weather, because colder temperatures cause the oil to congeal (thicken) to a greater extent.
The engine must reach normal operating temperature before it will run smoothly and dependably. Temperature is indicated by the cylinder-head temperature gauge. If the airplane is not equipped with this gauge, the oil temperature gauge must be used. Remember, in this case, that oil warms much slower in cold weather.
Before takeoff the pilot should perform all necessary checks for engine and airplane operation. Follow the manufacturer’s recommendations when performing all checks. Always use a checklist; do not rely on memory.
Engines Not Equipped with a Starter
Because of the hazards involved in hand starting airplane engines, every precaution should be exercised. The safety measures previously mentioned should be adhered to, and it is extremely important that a competent pilot be at the controls in the cockpit. Also, the person turning the propeller should be thoroughly familiar with the technique. The following are additional suggestions to aid in increasing the safety factor while hand starting airplanes.
The person who turns the propeller is in charge, and calls out the commands, “gas on, switch off, throttle closed, brakes set.” The pilot in the cockpit will check these items and repeat the phrase to assure that there is no misunderstanding. The person propping the airplane should push slightly on the airplane to assure that the brakes are set and are holding firmly. The switch and throttle must not be touched again until the person swinging the prop calls “contact.” The pilot will repeat “contact” and then turn on the switch in that sequence—never turn the switch on and then call “contact.”
For the person swinging the prop, a few simple precautions will help avoid accidents.
When touching a propeller, always assume that the switch is on, even though the pilot may confirm the statement “switch off.” The switches on many engine installations operate on the principle of short circuiting the current. If the switch is faulty, as sometimes happens, it can be in the “off” position and still permit the current to flow to the spark plugs.
Be sure to stand on firm ground. Slippery grass, mud, grease, or loose gravel could cause a slip or fall into or under the propeller.
Never allow any portion of the body to get into the propeller arc of rotation. This applies even though the engine is not being cranked; occasionally, a hot engine will backfire after shutdown when the propeller has almost stopped rotating.
Stand close enough to the propeller to be able to step away as it is pulled down. Standing too far away from the propeller requires leaning forward to reach it. This is an off-balance position and it is possible to fall into the blades as the engine starts. Stepping away after cranking is also a safeguard in the event the brakes do not hold when the engine starts.
When swinging the propeller, always move the blade downward by pushing with the palms of the hands. If the blade is moved upward, or gripped tightly with the fingers and backfiring occurs, it could cause broken fingers or the body to be pulled into the path of the propeller blades.
When removing the chocks from in front of the wheels, it should be remembered that the propeller, when revolving, is almost invisible. There are cases on record where someone intending to remove the chocks walked directly into the propeller.
Unsupervised “hand propping” of an airplane should not be attempted by inexperienced persons. Regardless of the experience level, it should never be attempted by anyone without adhering to adequate safety measures. Uninformed or inexperienced persons or nonpilot passengers should never handle the throttle, brakes, or switches during starting procedures. The airplane should be securely chocked or tied down, and great care should be exercised in setting the throttle. It may be well to turn the fuel selector valve to the “off” position after properly priming the engine and prior to actually attempting the hand start. After it starts, the engine will usually run long enough with the fuel “off” to permit walking around the propeller and turning the fuel selector to the “on” position.
Idling the Engine During Flight
There could be potential problems created by excessive idling of the engine during flight, particularly for long periods of time such as prolonged descents.
Whenever the throttle is closed during flight, the engine cools rapidly and vaporization of fuel is less complete. The airflow through the carburetor system under such conditions may not be of sufficient volume to assure a uniform mixture of fuel and air. Consequently, the engine may cease to operate because the mixture is too lean or too rich. Suddenly opening or closing the throttle could aggravate this condition, and the engine may cough once or twice, sputter, and stop.
Three precautions should be taken to prevent the engine from stopping while idling. First, make sure that the ground idling speed is properly adjusted. Second, do not open or close the throttle abruptly. Third, keep the engine warm during glides by frequently opening the throttle for a few seconds.