16 - Safety in General

  • Safety Articles

Hello everybody,

Whenever I send out a safety message, I get quite a few replies from members, and I would like to start by saying thank you very much to all of you who take the time to reply. I really do value your responses, both positive and negative, and particularly when you expand on my original message, or give further information.

Here is a rather longer reply than usual, but I would like everyone to see it, because it contains lots of useful and thought-provoking safety information.

As always, and in the time-honoured tradition of good safety culture, I keep the originator anonymous I always shall do this, unless contributors are obvious by their account and agree for their name to be published.

First thing. The bin is on the move. The Committee is well aware of the problem. It will probably go to the old tennis court, where blowing debris will not be a problem, and, more importantly, anybody ground-looping that far off the runway would have bigger things to worry about.

Fun flying to all,



Can we please go beyond the inane bull___ of endless tomes on supposed safety risks? These tend to simply turn off the audience instead of putting a safety message out.

First let's get something straight. Propellors don't kill. I've been carrying one in and out from my workshop as I refine its shape in preparation for refinishing. It hasn't hurt me, hasn't endangered me, quite the opposite, it is a hand crafted thing of beauty.

Trouble is that this guy (complaining about the dangers of propellers) is an idiot who has never taken the time to understand why propeller-strikes occur. They are entirely preventable accidents. Surely after pointing out the risk we should point out the steps to prevention?

}This is quite correct. I didn't spell out the steps to prevention because I assumed everybody was taught them when they first learned to fly, and I didn't think any of you would appreciate my attempting to teach you what you already knew. And most of them are just common sense.

}Nevertheless, in the interests of safety, some of the steps to prevention are:

}Never lean on a propeller.
}Never even go near a propeller, especially on a hot engine. If you do need to go near one, check that the magnetos are off, the mixture is to cut-off, the fuel is off and the throttle is closed. Ensure there is nobody in the aeroplane who might turn them on.
}Try not to pull an aeroplane by its propeller (they bend if they're aluminium, they snap if they're wood or carbon fibre, and you can damage the mechanism if they're constant-speed or variable pitch).
}If you do need to pull on a prop, do so only at the roots, and don't turn it, even a tiny bit.
}Never turn a propeller on an aeroplane when it's in the hangar (imagine the effect if the engine bursts into life).
}Don't turn a prop in the wrong direction if the engine has a vacuum pump (you can snap off the carbon vanes, so your gyro instruments will suddenly fail sometime soon (probably when you are relying on them).
}Never try to hand-swing a propeller unless you are either very familiar with this procedure, or have had proper instruction. Watching somebody else doing it is not proper instruction.
}If anybody out there can think of any more hints or tips on safe propeller handling, please let me know.

As to injuries, the short answer is that with the level of medical knowledge not present on the airfield such an injury would be fatal. So let's not worry about responding to the possibility of such an accident but put all our efforts into preventing one in the first place.

> My buddy John Watkins, a very experienced pilot, got his arm slashed to the bone by a Tiger Moth propeller as he was merely walking past and it kicked, just once.

Stop being sensationalist. Why did that occur? ...because of a fault in the p lead? surely a preventable problem overcome by competent maintenance. Point out to people how to check for p lead malfunction on shutdown. Also what is the engine telling you if during a runup there is absolutely no rpm drop when selecting each magneto?

}The Tiger prop that hit JW? Not a faulty P-lead. No maintenance problem at all. We took the aeroplane into the hangar after taking John to hospital, and even after a dozen of us and a couple of LAMEs had a good look, we could find nothing wrong.

}We concluded that there just must have been a glowing ember of carbon or something in the cylinder, and as the residual fuel air mixture warmed or cooled so the stoichiometric ratio came good, and it fired.

}After asking around, we found this is not such a rare occurrence, although the old Gipsy shut-down routine of opening the throttle after turning off the mags may contribute to it. That' s done to prevent 'running on' but causes the other, more rare problem.

}Trouble is, a prop can kick like that for maybe ten or fifteen minutes after shutdown, but some folk don't seem to know of this phenomenon.

}Prevention... a proper dead-cut check before shutting down... After stopping, but before shutting down, while you are letting your engine cool down, do another mag check, but at idle rpm.

}This will tell you if you have a mag, plug or lead problem in time to fix it before you next go flying.

}But, in addition, momentarily switch off both mags, then immediately switch them back on again. If the engine keeps running, you may have a faulty p-lead, so one of your mags is not earthing when you switch it off.

}This means that magneto is live all the time, and your prop is just an amputation waiting to happen (whoops, there I go, sensationalising again. But, I've seen the consequences).

}When you do your pre-flight mag check, if there is no rpm drop when you switch off one (or both) of the mags, one of your mags is live all the time. Ditto.

}I know of an Islander at Biggin Hill that had its left engine's mags wired to both sets of mag switches. This meant that the mag drops appeared identical on both engines during the mag checks. It also meant that both mags on the right engine were live all the time. And an Islander's engines are just above head height. Guess how the fault was discovered?

> Robin Owen lost three fingers to a Turbulent prop (Volkswagen engine)

Alan Usherwood's little starter mod shows that the root cause of this problem is quite simple to overcome. Don't hand prop an aircraft. ...if you do, make sure that the engine and prop is properly setup to allow it to happen safely.

}The trouble with starter motors is they're heavy. Even tiny modern ones have a significant weight. And they fit on the front of your aeroplane. The Fly Baby Rick and I share used to have one, but I had to remove it to get the weight down to a legal (and safe) level.

}I don't know what effect Alan's starter has on his Turb, but I am sure he has been careful with both its weight and C of G.

}Having a starter is one solution, but we all still need to be very careful of propellers.

}Hand-propping ("swinging propellers") is quite safe if you are careful and familiar with the process. Only one aeroplane I have owned has a starter, all the others have been hand swung. I have not been hit YET.

}Like Alan, I refuse to hand-swing a three-bladed prop (Robin's mistake).

}If anybody wants me to do so, I will happily ask Garth and Shelley to put on our web site an article I wrote years ago on how to safely swing a propeller.

}I have also written articles about checking out on taildraggers, and other technique tips. They can all go on the site if you want them.

and as a teenager I saw the consequences of an instructor losing his head to one on an idling Piper Colt.

Probably quite vivid in the imagination but surely painting the prop correctly would have made it visible when in motion? How many of the props on our airfield are adequately painted?

}This is another valid point, although prop painting has its limitations.

}The RAF paint their props with slightly offset black and white segments, and they look very visually obvious when they are running.

}I twice asked somebody to paint a new prop like that for me, but both guys refused because it was hard to do, and because they said it made balancing difficult.

}It also prevents a wooden prop being a thing of beauty, but I'll pursue that one.

}If anybody has the drawings (they were published in a UK Information Circular in the 1970s) that would be a great help.

}Unfortunately the instructor above approached the prop from behind, where it has to be matt black to prevent disorientating, and epilepsy-inducing flicker effects for the occupants. (The Colt had become bogged in snow, and the instructor hopped out to clear the snow away from the nose-wheel. Unfortunately he didn't shut down the engine first and leaned forward into the prop.) Yes, the resulting scene, on that silent, white, snowy airfield (Fairoaks, where I got my fist job, sweeping hangars and refuelling Tiger Moths) is etched permanently on my imagination.

Don't go anywhere near a propeller unless you have to, then treat it with enormous respect.

a meaningless crock of nonsense comment. The prop is no more dangerous than an aileron on a wing or a pitot tube hanging down under the wing. The potential accidents occur rarely because there is generally a competent awareness of how to prevent them. Work to ensure 100% awareness.

}I hope the above helps to achieve that.

Here is a real hazard you can work on. "all clear". What exactly does this mean? To experienced aviators the meaning is evident but to those at risk this is meaningless jargon. You'll find I call out "stand clear of the prop" which is meaningful to a nearby novice.

}Yes, I e-mailed everybody on this topic a month or so ago.

} I suggested we each come up with a form of words which could be understood by a novice before our Flying Weekend.

}I check the area in front of my Maule immediately before getting in, and quickly shout "Stand clear of the propeller" once I am in, if I think there might be anybody nearby who is not familiar with aeroplanes. Then I wait a few seconds for anybody to get clear before hitting the starter. }Does anybody else out there have any better ideas?

}Why aren't we all taught to do this?

You'll probably hate this email but I have left enough clues as to how an effective safety audit could proceed. I'll be watching :-)

}No, I loved it. We need more safety input.

}The safety sub-committee is not omnipotent.

}Please keep giving us feedback.

}Next week I shall be tackling the subject of safe fuel handing.

}All input appreciated.

Safe, and enjoyable flying to all.

Bob Grimstead
SABC Safety Committee