Was pulling a Gipsy Major through the other day for priming. It has a Fairey Reed prop and for me, requires quite a stretch to reach. Because of this, I found that I would be moving the prop in two separate movements for each pull through. The first is the big reach to be able to just get the blade to a position of about 2 o’clock, which is just prior to the click of the impulse coupling. I find that I have to grab the prop near the hub to do this.
Once positioned at the 2 o’clock position, then I pull it through carefully and start over again. But I did notice that I was pulling through with my hands about mid-way between hub and tip as that is where they were for the initial positioning of the propeller. While doing this, I was thinking about the incident mentioned in the previous post.
I noticed that even though I was only just wrapping the very tips of my fingers onto the trailing edge of the blade, because of the increased twist of the blade at the mid-point versus near the tip, it seemed I was more vulnerable to having my fingers struck by the next blade if the engine started suddenly. Therefore, for the rest of the pull-throughs, I made sure to take the time to make sure I was pulling from as close to the propeller tip as possible, even if it took a bit longer to do the whole procedure. As a benefit, the prop requires less force to pull through when hands are close to the tip.
Update Nov 17/2022:
Well folks, it actually did happen. I ended up with a live mag on the Gipsy Major and had it fire on me.
The pilot flying the aircraft came in and did a pre-flight. Part of his pre-flight is to actually remove the earthing cap for each mag and lake a look at the interior of the cap(it has a spring and carbon brush and he once found the spring broken on a pre-flight). Both caps were placed back in position. I was the ground crewman for the start. What neither of us knew was that the mag on the starboard side of the engine was live. As the pilot was setting himself up in the cockpit, I confirmed that the throttle was closed, brakes set, fuel selector off, and mag switches off. I carefully pulled the prop through several times as a standard(but unlikely to find) check for a hydraulic lock. All seemed normal with a few clicks heard to confirm impulse operation. The pilot said that he was ready for the engine to be primed. I pulled on the cable to overflow the carb which allows fuel to flow into the intake manifold. When I saw fuel coming out the intake manifold drain, I proceeded to the prop to start turning it which allows the suction from intake strokes to suck in fumes for start,
Because the prop is quite high and in a near vertical position(a blade at 1 o'clock position), I have to reach up and grab the inner part of the prop and move it clockwise to near the horizontal position which is just prior to an impulse click - which is a spark in one of the four cylinders as each sequential click fires a different cylinder(keep in mind that most British engines turn in the opposite direction to American engines). I don't have to worry about the non-impulse mag, even if is live, as prop is being turned too slow to activate it. But unknown to us, the impulse mag is hot.
I pull the prop through twice, each time it ends up near vertical and has to be re-positioned to near horizontal for the next pull through. On the fateful pull, I grab the prop with both hands near the tip as there is less twist at that location meaning my hands are further forward a bit from any sudden, fast start(like Kinners tend to do). My fingers are not wrapped all the way around the trailing edge but just enough to be able to pull the prop through. And then it happens. There is a single fire and the propeller kicks backward(not 100% sure why yet) but for a fraction of a second, I thought it was a hydraulic lock I hit but the prop pulls away backwards out of my grasp. There is no pain or issue as I did not have my fingers wrapped around the prop(remember, the trailing edge is sharper than the leading edge).
The engine is started and there is a live mag as it has to be shut down by turning the fuel selector off. It turns out that there is an exposed wire on the starboard earthing cap, that perhaps became exposed when it was removed for inspection.
Last edited by punkalouver; 18th Nov 2023 at 01:54.