A spinning propeller can be lethal should it strike someone. Historically, when aircraft lacked electrical systems, it was necessary to “hand prop” an aircraft for starting. Hand propping an aircraft is a hazardous procedure when done perfectly. The consequences of not mitigating the hazards associated with hand propping can lead to serious injury, fatalities, and runaway airplanes. All alternatives must be considered prior to hand propping an aircraft and, when a decision is made to do so, the procedure must be carried out only by competent persons who have been trained to accomplish the procedure, understand how to mitigate the hazards, and take all the necessary precautions.
Even though today most airplanes are equipped with electric starters, it is still helpful if a pilot is familiar with the procedures and dangers involved in starting an aircraft engine by turning the propeller by hand; however, a person unfamiliar with the controls must never be allowed to occupy the pilot’s seat when hand propping.
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It is critical that the procedure never be attempted alone. Hand propping should only be attempted when two properly trained people, both familiar and experienced with the airplane and hand propping techniques, are available to perform the procedure. The first person is responsible for directing the procedure including pulling the propeller blades through. The second person must be seated in the airplane to ensure that the brakes are set, and controls are properly exercised, and to follow direction of the person pulling the propeller.
When hand propping is necessary, the ground surface near the propeller should be stable and free of debris—loose gravel, wet grass, mud, oil, ice, or snow might cause the person pulling the propeller through to slip into the rotating blades as the engine starts. Unless a firm footing is available, relocate the airplane to mitigate this dire consequences hazard.
Both participants should discuss the procedure and agree on voice commands and expected action. To begin the procedure, the fuel system and engine controls (tank selector, primer, pump, throttle, and mixture) are set for a normal start. The ignition/magneto switch should be checked to be sure that it is OFF. Then the descending propeller blade should be rotated so that it assumes a position slightly above the horizontal. The person doing the hand propping should face the descending blade squarely and stand slightly less than one arm’s length from the blade. If a stance too far away were assumed, it would be necessary to lean forward in an unbalanced condition to reach the blade, which may cause the person to fall forward into the rotating blades when the engine starts.
The procedure and commands for hand propping are:
- Person out front says, “GAS ON, SWITCH OFF, THROTTLE CLOSED, BRAKES SET.”
- Pilot seat occupant, after making sure the fuel is ON, mixture is RICH, magneto switch is OFF, throttle is CLOSED, and brakes are SET, says, “GAS ON, SWITCH OFF, THROTTLE CLOSED, BRAKES SET.”
- Person out front, after pulling the propeller through to prime the engine says, “BRAKES AND CONTACT.”
- Pilot seat occupant checks the brakes SET and turns the magnetos switch ON, then says, “BRAKES AND CONTACT.”
The propeller is swung by forcing the blade downward rapidly, pushing with the palms of both hands. If the blade is gripped tightly with the fingers, the person’s body may be drawn into the propeller blades should the engine misfire and rotate momentarily in the opposite direction. As the blade is pushed down, the person should step backward, away from the propeller. If the engine does not start, the propeller should not be repositioned for another attempt until it is verified that the magneto switch is turned OFF.
The words CONTACT (magnetos ON) and SWITCH OFF (magnetos OFF) are used because they are significantly different from each other. Under noisy conditions or high winds, the words CONTACT and SWITCH OFF are less likely to be misunderstood than SWITCH ON and SWITCH OFF.
When removing the wheel chocks or untying the tail after the engine starts, it is critical that everyone involved remember that the propeller is nearly invisible. Serious injuries and fatalities have occurred when people who have just started an engine walk or reach into the propeller arc to remove the chocks, reach the cabin, or in an attempt to reach the tail of the airplane. Before the wheel chocks are removed, the throttle should be set to idle and the chocks approached only from the rear of the propeller. One should never approach the wheel chocks from the front or the side.
The procedures for hand propping should always be in accordance with the AFM/POH and only accomplished if no alternatives are available, and then only by persons who are competent with hand propping procedures. The consequences of the hazards associated with hand propping are serious to fatal.