nuts & bolts

technical counselor Hand Propping Gone Bad Don’t let it happen to you J. KENTON, EA A 313747

I

t was about 8 a.m. on a weekday morning and no one was at the airport except a couple of the staff at the far end. I was strapped into my plane and ready to go. When I hit the starter, it engaged, but it barely turned the prop. My thought was a possible hydraulic lock, so I got out to turn the prop by hand. It moved, but I could hear the sound of the Bendix starter as the prop turned. That was a hint of my

problem, but I was oblivious to it. A month earlier, I had left the battery switch on and depleted the battery, then recharged it and flew a two-hour cross-country, stayed 24 hours, and flew back. No problem. In fact, two days later I was back at the plane and cranked it up just to taxi to the fuel pumps and back. Everything was fine. Now it was three weeks later and the engine wasn’t turning over. I got back in the plane for another try. Still nothing.

Bonnie Kratz

Joe Norris demonstrates how to hand prop an airplane.

96

JULY 2009

I’d hand-propped this engine before. It is a 150-hp O-320, the lower compression engine that was designed for 80/87 avgas. Before trying to prop it, I moved the plane over to an empty tie-down area and ran a tie-down chain around the tail wheel. I made a kind of double slipknot of the chain so I wouldn’t have a lot of trouble untying it after the engine was running. (I didn’t bother chocking the plane because the chain was on the tail wheel.) I set the throttle and mixture just as I normally would, gave it a few more shots of primer, and went out front to prop the engine. I could still feel the Bendix dragging and wasn’t sure I could get enough “umph” for it to fire. About the eighth or 10th try it fired. It was at a higher rpm than I was comfortable with (but that’s how I normally start, with an immediate reduction because I’m normally in the cockpit), and

I moved briskly to get around the wing and to the cockpit. The plane moved forward as I started around the wing, and I was surprised to see the chain’s steel loops were not tightening into a holding position as a rope would do. Instead, the chain was sliding through the loops

I had made and was untying itself! Before I could get to the cockpit, the tie-down chain had come undone and the plane was moving without me. I managed to grab the aft part of the open canopy and tried to pull myself forward. Instead of slowing the plane, or getting

EAA Sport Aviation

97

technical counselor onto the wing, I lost my footing and found myself being dragged by the plane. I may have held on for some 10 seconds before realizing the futility of being dragged. After letting go, I had a moment to wonder where the plane would go, while simultaneously thinking how stupid I’d been to not use chocks along with the chain. Looking at the airplane running free, a moment was all that I had. The plane had been pointed on a diagonal toward the runway, but because of my dragging from the left side, it was now making a left turn and looking as though it was going to come back at me. My hands and knees were hurting, but the thought of being on the ground while that whirling propeller made its way toward me was enough to get me back up. I was able to get to the front of the left wing, outboard of the propeller arc, and slow the plane, make it turn more tightly, and—most of all—get onto the wing and reach in and close the throttle. A month later, my knees were still healing. Still, I couldn’t believe my good fortune. There had been no one around to help me. I had approached this event with a complacent attitude and did not make an effort to chock the plane— the simple thing that could have prevented all this. I could have even run the chain around in a simple granny knot, and it may have held. From all my time in aviation, there are two issues that stick in my mind when it comes to preventing accidents. The first is complacency, when we start feeling that something is so routine we needn’t scrutinize it closely. The second is the timeworn issue of accidents often resulting from a chain of events. Break the chain at some point, and the accident won’t happen. In my case, the chain of events was the things I didn’t do. 98

JULY 2009

11 Hand-propping Guidelines By Tim Hoversten, EAA 597473 EAA Technical Aviation Specialist 1) Before hand-propping on your own, get trained in the proper technique. This is serious business, and as with most things aviation-related, there is no substitute for training. 2) If you can avoid it, never prop alone. However, if you have no choice, always tie the tail. Never try to start solo if the tail is not tied down! 3) Before touching the prop, make sure the plane is secured from movement—tail tied down, chocks in place, and/or person on the brakes. 4) Any time you touch a propeller, you are propping it—treat it as if it’s hot regardless of what the mag switch says. While mechanical malfunctions are rare, wiring can loosen, throttle cables can become disconnected, and brakes may fail. Be aware and reduce the risk as much as possible. 5) The person touching the prop is in charge, and clear communication with the person at the controls is vital. 6) Brief the person at the controls on the proper sequence for starting, and on where controls, brakes, and switches are located. Make sure the person at the controls is absolutely clear about what to do should something go wrong…and about what to do after a successful start. Have the person repeat verbal commands and rehearse the procedure until you are convinced he or she is properly trained. 7) After going through the drill, make sure both of you are completely focused on the job at hand, with no distractions, and can clearly hear each other. 8) Clear the area, and make sure you and others stay clear of the prop arc. Unless you are propping an aircraft with a long prop and radial engine, stand between the prop and the leading edge of the wing, establish a firm footing, and swing the prop using one hand on the prop and one hand on the cowl. 9) Never lean into the prop, and position the prop accurately for the start after pulling through to prime the engine—always remembering to treat it as “hot” throughout, even with the switches off. After priming, turn off the fuel! Should the engine start inadvertently, or if the throttle is opened too far, the engine will soon quit, rather than running until the tank is dry. 10) Do not hand-prop at night. 11) Star t on grass rather than concrete, if possible. EAA Sport Aviation

99