Eye of Experience #39:
Those Dangerous Props

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Despite the relative safety of general aviation, each year several people are injured or killed on the ground by spinning propellers. Plus, when it comes to hand-propping engines to get them started, there are all kinds of dangers involved. AVweb's Howard Fried takes a look at the

Eye Of ExperienceProbably the most dangerous thing about general aviation is that one must be around propellers -- after all, they are attached to airplanes -- and when a human being encounters a rotating propeller, the prop invariably wins. The result is usually disastrous to some part of the human body. I personally know two -- not one, but two -- one-armed flight instructors, each of whom donated an arm to a propeller. I am also acquainted with one fatal encounter with a prop and another very serious injury. Another acquaintance, a flight instructor, caused a great deal of damage when he hand-propped an airplane that started up and proceeded across the ramp, striking and severely damaging two other airplanes. In another instance, an airplane taxied down a narrow taxiway damaging an entire row of airplanes tied down alongside.

Frequency

Although not a really big factor in the total general aviation accident picture, encounters between props and people continue to occur, and when they do they are almost always invariably fatal. Such encounters account for the majority of airplane accidents that occur on the ground. Some 15 percent of prop injuries are the result of pilots attempting to start an airplane by hand-propping it without a competent individual at the controls, but the majority result from pilots or passengers deplaning while a prop is spinning or from pedestrians crossing the ramp when an idling or taxiing airplane can strike them with its dangerous weapon -- the prop. The FAA has an excellent movie clip of what can happen when an airplane is propped without a qualified person at the controls. If you haven't already seen it, be sure to do so. The Safety Program Manager at your local FSDO (Flight Standards District Office) either has one or can readily obtain it for you, and it is well worth viewing.

Hand-Propping

Back in the "good old days" when the J-3 Cub and the 7AC Champ were the primary trainers in general use throughout the land, everybody was trained in the proper procedure for propping an airplane, since the trainers didn't have electric systems and, hence, they lacked starters. (Larger trainers had inertial starters, which required quite a bit of muscle power to wind up.) Thus, students of that era were taught from the very start not only how to properly hand-prop an airplane to start it, but to respect the propeller. Today, one of the most common types of accidents involving contact between a spinning prop and some part of the human anatomy occurs when an individual is attempting to start an airplane by propping it.

I believe that all pilots who operate light airplanes (200 HP or less) should be properly trained in hand-propping techniques and procedures, and most modern pilots have never been so taught. This is no doubt because most modern instructors don't teach this because they were never taught themselves. Since one never knows when it might become necessary, it is something everyone should know. A few years ago the former office manager of our local FSDO told the following story to a group of DPEs (Designated Pilot Examiners):

Before he joined the FAA, he had been a civilian pilot examiner. One day, a young lady came to him for a private check ride. She had brought a Cub (no starter), and after the completion of the oral portion of the examination, they went out to the airplane. The applicant performed a satisfactory pre-flight inspection, climbed into the rear seat, buckled up, and sat there. The examiner asked her if she didn't intend to start the airplane. She replied that her instructor had always done that for her, and had never taught her how to do it. The examiner inquired as to what she had done when off on a solo cross-country flight or her instructor was otherwise not available. Her answer was that she had always been able to find someone willing to do it for her. I guess she must have been quite an attractive young lady. In any event, the examiner disapproved her application and sent her back to her instructor for more training. I wonder just what this young lady expected to do when -- not if -- she found herself in a situation where it was necessary to start an airplane and there was no one around to prop it for her.

Personally, I'm terrified of props. I guess I'm actually paranoid -- I believe every propeller on the airport is alive and out to get me. I walk around airports looking over my shoulder, waiting to be attacked by a spinning prop. This doesn't mean I won't hand-prop an airplane -- I will, but I do so very, very carefully. I have performed this task hundreds, even thousands of times, for I gave many hundreds of hours of dual instruction in J3 Cubs and 7AC Champs, neither of which has an electrical system or starter.

Proper Procedure

Propping is not particularly complex, no is it particularly difficult, but it does require extreme care, and there are certain procedures which should be followed:

  1. One should always assume that the prop is hot (alive) and may start of its own volition at any time.
  2. There should always be a knowledgeable person inside the airplane at the controls. Most hand-propping accidents occur when an unattended airplane is propped or an unqualified person is at the controls. If it is not possible to have a qualified person at the controls, the airplane should be firmly secured, and I don't mean merely chocked, but actually tied down, and the airplane should be on a firm, level surface. You don't want to slip and fall into the spinning prop.
  3. Photo courtesy Andy AllenAlways assume the prop is hot.
  4. Communications between the person inside the airplane at the controls and the one doing the propping must be crystal clear. There must be absolutely no misunderstanding regarding whether or not the magneto switch is on or off.
  5. Always assume the prop is hot.
  6. With the switch off, grasp the prop near the hub and give a good healthy tug to make sure the airplane is firmly anchored (brakes being held by person inside, or securely tied down-- preferably both).
  7. Always assume the prop is hot.
  8. With fingers flat on the blade (not wrapped around the edge of the prop blade), and the switch off, the prop should be pulled through. This will serve to prime the engine and to give the person doing the propping a feel for the compression resistance offered by the engine. This "pulling through" should be stopped at the top of a compression stroke of the engine.
  9. Always assume the prop is hot.
  10. Call for "Switch on" or "Contact" and receive acknowledgment from the responsible person at the controls.
  11. Now you know the prop is hot.
  12. Then, with the mag switch on and fingers flat on the blade, not curled around it, the prop should be sharply pulled through again as the one propping the airplane steps back away from the airplane (and the propeller).
  13. Always assume the prop is hot. (Are you getting a message here?)
  14. If the engine fails to start, the procedure should be repeated until it does.

More Points

Normally, of course, an airplane is hand-propped from the front, but there are situations when an airplane must (or should) be propped from behind. For a few years we used a Taylorcraft BC12D (no starter) with Edo floats for the trainer on our seaplane curriculum. With the airplane floating on the water, the technique involved standing on the right float, grasping the wing strut with the left hand, and propping the airplane from behind the prop with the right hand, then scrambling across the right seat to settle in the left seat as the airplane taxied slowly across the lake (or other body of water). By the bye, this airplane had a great big 85-HP engine (it was certified with a 65-HP powerplant) and was an excellent performer on floats. For several years I had a Mooney Model 18 (a Mooney Mite), a one-place airplane that I kept as my personal toy. It, too, lacked a starter and had to be hand-propped. I found the best way to do this was also to prop it from the rear. I would stand with my butt against the right wing root and my left hand at the base of the windscreen, and prop the airplane with my right hand.

The FAA recommends, and I think it's a good idea, that prior to start-up one should always turn on the rotating or flashing beacon to alert anyone outside that the prop is about to be set in motion. Also, it is imperative that an airplane only be started when the area behind it is clear. I have observed careless pilots start an airplane with its rear end pointed at an open hangar, and blow dust, sand and gravel into the hangar, damaging airplanes inside.

You Can't Fool Your Old Dad

Of course, starting an airplane parked on a sandy or gravel surface can seriously damage the prop. (When flying in Australia, I was told that since many of the unimproved sod strips aren't really sod at all, but gravel, it is necessary to replace props often.) Even starting or taxiing through puddles of water can, and often does, damage props. And, of course, if an airplane is started or run-up with spectators standing nearby (to the rear), the people there can be hit by flying debris. Even when the area is clear, it is best to start up and taxi using the absolute minimum of power necessary, until you are in a clear area on a firm surface and you are ready for the engine run-up.

Several years ago a renter pilot had taken one of our school airplane from Michigan to Florida. On the way back he made a fuel stop at Charlie West (Charleston, West Virginia). When departing that airport, he thoughtlessly accomplished his run-up at a location where there were several spectators standing behind the airplane, blowing sand and small stones back into the crowd. By happenstance, unknown to the careless pilot, another of our customers was there and observed this. The witness returned first and reported the matter to me. When the guilty pilot got back I greeted him and counseled him rather severely regarding what he had done. He said, "Gee whiz, Howard, do you have spies everywhere?"

I replied, "Of course I do! Don't think for a second that you can get away with anything without your Old Dad finding out."

I'm sure that pilot never again has started an airplane without first carefully checking the area all around.

Care Of The Propeller

Finally, it goes without saying that any nicks in the prop blades should be thoroughly dressed down with a file to prevent a crack expanding into a fractured blade. Airplanes don't fly very well with less than full-length prop blades, and the resulting unscheduled landing can be harmful to the overall health of the human anatomy. I remember an occasion many years ago when I was alone flying a J-3 Cub with a wooden prop. The metal binding around the tip of one of the blades separated and departed in flight. The resulting vibration from the imbalance was enormous. It happened shortly after takeoff and, with great care, I managed to nurse the airplane around to a safe landing on the airport. On examination, the first several inches of the prop blade looked like a bunch of wooden toothpicks. It was pure luck that the vibration hadn't shaken the engine loose from its mounts. When an airplane sheds a prop blade it is a good idea to shut down the engine and turn the airplane into a glider. It may not be a very efficient glider, but it will glide to (hopefully) a safe unscheduled landing.


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