A Dozen Rules to Spin a Prop

I looked at my Facebook page yesterday and found a photo of a pilot who lost the tip of a finger while hand propping his ultralight airplane. Pretty gruesome stuff. I often tell my students that hand propping an airplane is very safe – and then in my next breath, I report it is the most dangerous thing a pilot can attempt.

Indeed, had the early aviators not been willing to prop off their airplanes, we never would have gotten off the ground. Even as late as the early 1970’s, some of us had to swing our props in flight school in order to learn how to fly.

Hand propping an airplane to start it is much the same as flying in the first place. There are those who say flying is dangerous. It is, and it is not. Flying, like hand starting an airplane, is only as dangerous as the participants allow.

Most airplanes that require the “Armstrong” technique to start, fall into three broad categories. The first include the originals. These are the Cubs, Champs, Luscombes, Aeroncas and other airplanes powered by the Continental A-65 engine of 65 horsepower. This engine, as small as it is, lacks provisions for an accessory housing to allow for extras, like a starter or generator.

Another group of planes started by hand includes the new breed of ultralights, and the Light Sport Aircraft (LSA). Small engines of the Rotax, VW, or Subaru variants power these planes. Like their brethren A-65s, they are lightweight and usually don’t have the capability to carry the weight of batteries and alternators/generators.

Most of these aircraft are taildraggers, which allow easy and safe hand starting. The next group of airplanes typically in need of manual starting includes the aerobatic thoroughbreds. Because experienced pilots fly these airplanes, there are fewer problems or incidents regarding the manual starting of these craft.

Aerobatic airplanes need to be hand cranked because the competitive pilots flying them cannot afford to carry the extra weight of an electrical system and batteries. In competitive flying, any extra weight is a handicap for the serious aviator.

It is the “not so serious” aviator who can be a dangerous consideration in this business. Pilots who do not follow the rules may place a burden on all the rest of us. The most dangerous and annoying thing experienced aviators must occasionally deal with is the inexperienced pilot who believes they know what they are doing when it comes to hand starting their airplane, the one with the dead battery.

Too many times, pilots who are confident and comfortable with starting airplanes by hand propping sometimes come onto a situation no one likes to see. The pilot, who fails to use his checklist properly, leaving the master switch on after shutdown, or the pilot flying an airplane with a temperamental battery, may find themselves in the predicament of having to hand crank their plane. There is usually nothing wrong with this, if the pilot is experienced. The inexperienced pilot is the one who presents a problem.

Lately, it seems as though the media has reported too many instances of a pilot manipulating a prop on an airplane with an incompetent person at the flight controls. (Keep in mind that incompetent in this case means someone not trained, certificated, knowledgeable, or qualified to stand duty in the cockpit.) Or there is the story of the pilot who tries to start an airplane alone, and it manages to fly off – pilotless. There is only one situation worse than this: It is the airplane that takes off with a non-pilot in the cabin who has no idea of what to do. There are also the very horrid stories of pilots or passengers who walked into the prop arc of a turning propeller.

If you are going to try hand propping your airplane, there are certain rules you must follow.

Rule No. 1: If you have never done it, DO NOT DO IT! At least not until you have training in the correct technique. If you are a leery about handling a propeller, congratulations, you have the required common sense for training. Those who believe they know how to prop an airplane and actually have no idea of what they are doing often scare all the experienced aviators around them. There have been several cases involving a new pilot attempting to prop an aircraft while completely ignorant of the procedure. If they are lucky, some old and experienced salt will come along to help.

Again to emphasize – and this is important – if you don’t know how to hand prop an engine, don’t try!

Rule No. 2: Handle all propellers as though they are a live alligator about to bite off your hand. Looking at an airplane propeller without knowing the mag switch position is a lot like trying to judge a book by its cover. From the outside, you cannot tell if the mags are off, or if the ground is sound. Therefore, until proven otherwise, all props are hot and you should treat them accordingly.

Rule No. 3: Always have a competent partner, brief each engine start, and use proper commands. If your spouse or current love interest is a licensed pilot, then then they are OK to perform cockpit duties. However, student pilots and non-pilots may not be competent to manage the cockpit while you are out spinning the fan.

When it comes time to start, a pre-start briefing between starter and the brake-rider is important. Each engine start, like each flight, is different. These differences need discussing before the engine start. The commands used by each person involved in the engine start must be uniform and common. More to follow on the commands.

Rule No. 4: Never extend appendages into the prop arc. As pilots, we are responsible all safety around airplanes. We must also make certain all our passengers understand the dangers of sticking an arm, leg, or head in the way of a propeller.

Rule No. 5: Have firm footing. Pre-flight the airplane’s parking area. If there is loose gravel or a puddle of oil or water making the ramp slick, move the airplane. When you start the aircraft, you do not want to slip under the rotating propeller.

Rule No. 6: When gripping the propeller blade, never grip the blade with your fingers “hooked” over the trailing edge. The correct technique is to place the pads of your fingers on the blade face just under the trailing edge on the face of the blade. If the engine “kicks back,” you will be unpleasantly surprised, but should not be hurt.

Rule No. 7: Never lean into the propeller. Novice prop-turners believe the farther away they stand from the propeller, the safer. This is not necessarily so. If the prop-turner stands too far away, they may be off balance and actually fall into the spinning prop after engine start. Stand at a comfortable distance from the propeller with firm footing and an erect posture. While pulling the propeller through, do so in a way allowing yourself to push away from the prop.

Rule No. 8: Never try to brief the line attendant, your spouse, or anyone else who knows nothing about airplanes and then ask them to throw the prop for you while you sit in the cockpit. This is very dangerous. Postpone the flight, find someone else to help you start the aircraft, or use the solo techniques of Rule No. 10 for the engine start.

Rule No. 9: Position the propeller accurately for the start. This begins with priming the engine by pulling it through a few times – with the magneto switch in the off position. While doing this, remember Rule No. 2 and always consider the prop “hot.”

Rule No. 10: If you can avoid it, never prop alone. If you have no option and must hand-start your aircraft solo, chock the wheels and tie the tail. NEVER prop an aircraft solo without the tail tied down! When starting the airplane alone, use a slipknot in the tail tiedown with a length of rope long enough to reach the cockpit. Once you have the engine running, make sure the throttle is all the way back to idle and remove the chocks. Then you can take that length of rope into the cockpit with you and pull the slipknot free after you are safely inside at the controls.

Rule No. 11: If able, start the airplane in the grass rather than on concrete. Grass has a higher coefficient of friction than a hard surface.

Rule No. 12: Avoid hand propping at night. In the dark, there are things out there you cannot see and one of those things is the prop arc. Typically more than a quarter of the prop accidents happen in the dark.

Okay, so now you know the rules. How do you do it? What are the commands?

Throughout the procedure, the person in command of the starting sequence is the one actually throwing the prop. The pilot in the cockpit should follow each command precisely and reply loudly enough to allow the brake rider to hear over the ambient noise. With all the preliminaries taken care of, such as the pre-start brief and acknowledgement of who is in charge, it is time to start the engine.

The person who will prop the airplane now yells, “SWITCH IS OFF!” After the checking the switches to the off position, the pilot replies, “Switch off.” The prop-swinger then pulls the propeller through by hand to prime the carburetor. Next, the prop-thrower positions the prop for the start by bringing it around to the beginning of a compression stroke. This places a blade conveniently at about the ten o’clock position.

Then the prop-thrower commands, “BRAKES.” The pilot replies, “Brakes set.” Before each start attempt, the prop-thrower tests the brakes by pushing on the aircraft to make certain it does not move. After assuring himself the brakes are locked, he yells, “CONTACT!” The reply, of course, is “Contact!”

Everyone must now understand that the prop is hot and the engine ready to start. With an easy pull of the blade, the engine will start. Now the person throwing the blade needs to be careful to avoid the whirling disc as he walks clear to either climb into the aircraft or return to other duties.

To reiterate, hand propping an airplane is a risk and is in fact, dangerous. However, pilots can minimize and manage the risks. Be safe, go slow, and always think about what you are doing, or are about to do. You must never take chances if you are going to start your engine by hand. More importantly, you must always keep in mind the safety of your passengers.

It goes without saying that as long as you use sound common sense, there is no reason to put yourself, your loved ones, or your aircraft at risk. Most importantly, never put innocent bystanders at risk while starting your airplane by hand.


©2015 J. Clark

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