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How To Start A Reciprocating Aircraft Engine

By: Luat Tran Van

Starting an aeronautical conventional engine is a rather simple procedure if it has a starter; but if you have to resort to hand propping, you should take some precautions and follow a carefully rehearsed technique, and this is the recommended method.
Before we start this discussion lets remember that a propeller is an extremely dangerous device for any animal or person once the engine of an aircraft is on. A typical propeller like those used in small GA airplanes weights between seven and eleven kilograms and on idle will turn at about 500RPM; we need not explain what could happen to anyone or anything crossing by accident its path. All propellers should be treated as dangerous even if the plane is located inside a hangar and every system and instrument is thought to be disconnected; never let anyone get close or touch a propeller. Thus, it is indispensable not to attempt to hand prop an airplane without proper training; in the case of vintage or classic aircraft, certified pilots would almost surely have received that training. Aviators using conventional-gear aircraft will likely have it too. But pilots that always flew with tricycle-geared planes may or may not have learned how to hand prop an aircraft to start its engine manually and may find it attractive to put their vehicle to work in the case that the electric starter malfunctions for any reason.

These pilots should be careful and prudent, and get the indicated training before attempting to do something that looks easy, is easy once you get the hand of it but could cause serious accidents if improperly done. We must also stress that hand propping will hardly work in the case of engines of about 125 HP and over because the required force to turn the prop is too great. Thus, this method in such cases may not be advisable even if it is possible to actually move the propeller by hand because the additional force may cause an imposture or various other errors that could cause an accident. Even one person can hand pro and star an engine without an electrical starter, but the method is not considered safe at all. We will describe the basic method that requires two people - the pilot and what we shall call the engine starting director -, but we insist on the fact then if you have never attempted to start an engine by hand, get proper training given by a competent instructor. Having said so, let's start by assuming the following:
- You have finished your pre-flight check.
- You have secured the parking position by placing chocks on the wheels, getting a fire extinguisher and so on.
You should not attempt to star any engine - either electrically or manually started - unless these requisites have been duly fulfilled.

Once that is done the pilot jumps into the cockpit and proceed to finish any pending pre-flight check if the operation's manual requires it. He will check that the fuel valve is open and that the magneto selector is in the off position. He will have to control the parking area visually, including the actions of his companion who will actually manipulate the propeller, that is, the starting director. Once all that is also accomplished, the pilot will make sure that the throttle is placed on the idle position and the magneto selector is in "Off"; we insist a lot with this, but it is for safety reasons. Particularly if there are kids around or in the airplane, you should be very cautious and never assume that what you checked five minutes ago - like a key or lever - will remain in the same position or status. From then on, the person who will actually move the propeller by hand will act as the director of the operation, taking control of it and telling the pilot what to do. Of course, the pilot in command remains the responsible person so if he or she sees anything unsatisfactory with the behaviour or performance of the engine, or anything else, the whole operation may be aborted on his command.

The director then will begin by saying:
- "Magnetos off, idle throttle, brakes on."
And as he controls visually each item, the pilot will answer:
- "Magnetos off…idle…brakes on."
It is important to stress that the answers of the pilot must not be automatic; that could become a very dangerous habit. The pilot shall answer in a loud voice telling those words only if he has checked visually and appropriately every thing requested. That is, he would not say that the magneto key is off because he so it that way five minutes ago; he must actually check the key again. Be like a paranoid and you will be safe! The idea of the instructions given is to place the aircraft in a situation in which handling the prop without actually starting the engine will be possible. Then the director will likely move the prop a few times - usually as many as the number of cylinders that the engine has. In this way he will notice if the compression on each cycle performed by each cylinder is okay, and that the propeller is able to turn smoothly.

The director should be wearing comfortable clothes at the time, with no chains or jewellery hanging, no rings or anything else that could get hit, stuck in or sucked by the propeller. Balance and equilibrium are fundamental during this process and he will have to stand about half an arm's length from the prop, in front of it and facing the cockpit. In this way he will be able to step back safely as he attempts to start the prop by grasping a blade with both his hands and moving them energetically downwards and outwards. Once he has cycled the engine a few times with the magnetos off, he will accommodate the blade that he will actually grab for starting the engine, placing it in a position such as he will be able to fetch it with his arms up, but not so high as to be uncomfortable. Then he will say:
- "Both magnetos on, one fourth, two injections, stick back."
This means that he is asking the pilot to turn the magnetos to the "Both position" and open the throttle one fourth of its arc or span. From this moment on the engine is theoretically able to start at any moment. Asking for two injections means that he wants the pilot to use the primer twice; it is normal to prime the engine once to six times. So after placing the magneto key in the "Both" position (in these engines, there is no actual "Start" position since there is no electrical starter). The stick should be held back in the case of airplanes with conventional gear (taildraggers) so that in the even to an accidental movement or acceleration of the engine of the plane control over it will be held and the tail will not stand up.

The pilot will step on the brakes no matter whether he has or hasn't place chocks on the main wheels; then he will open the throttle as much as the director asks and inject the fuel using the primer. After each step is completed he will answer loudly:
- "Magnetos both... one fourth throttle, brakes on... two injections..."
Bear in mind that after the magneto key is placed in any position except off and the throttle is opened the engine may start if anyone touches the propeller. If the engine is in a good shape, only one or two "kicks" to the propeller will do the job and the thing will be running in a couple of seconds. If it is very cold, hot or if the engine is not in optimal conditions, tuned, etc. the process of had propping may take longer. So, the director will then perform a last check of the airplane's surrounding to determine if nobody is near the propeller in a dangerous position and then he will say loudly, for anybody to hear:
- "Free!" This is like saying "Watch out!"
Then the pilot will make his own check in response to the director's actions, and if he is satisfied, he will respond in the same way. After hearing confirmation from the pilot, the director will start with the first kick or action on any of the propeller's blades. This seems like a lot of work but the goal is to maximise safety; hand propping could indeed become hazardous, but if it is performed like a meticulous process, the danger is reduced in every way possible. Once again we insist that you never attempt to hand prop an airplane unless you have received proper and specific training. Being a pilot is not enough, having seen how others do it isn't either, as it is thinking that you can do it just because you think so.

The actual propeller kick will be performed at about half an arm's length from the propeller. The blade should be rather high, at about ten o'clock. Arms should be slightly flexed and the propeller should be grasped with both hands open, wearing no gloves or anything else that might change the touch. Most propellers turn clockwise from the perspective of the pilot, albeit in the case of vintage airplanes, some experimentals and in some special cases, props may turn counter clockwise. This means, from the perspective of the director, exactly the same: He will have to kick the prop counter clockwise, of course. If the engine turns into the opposite direction then the work will be done in the opposite direction too but it will remain essentially the same. So, the direct, wearing no gloves, rings or anything that may turn his grasp ineffective in any way. The propeller blade may have sharp edges, so be careful. Both hands should be placed with the palms open over the side of the blade and only the point of the fingers should be bent over the edges. The required force and work to actuate the magnetos is not much: The idea is to make the propeller turn only one cycle, which means that in the case of a four cylinder engine, ninety degrees will be enough. Each time the directors kick the propeller, he will have to step backwards. Of course, if the engine does

Article Source: http://www.articlemanual.com

You can find pictures explaining how to check an airplane at Andinia.com.



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