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Safety around propellers

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Safety around propellers

Old 15th Oct 2019, 12:29
  #121 (permalink)  
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Join Date: Aug 2006
Location: Ontario, Canada
Age: 60
Posts: 4,892
In piloting, we consider "normal" and "abnormal" conditions. When presented with an "abnormal" condition, we exercise more caution, as an accident is more possible. A turning propeller, with people moving around near it on the ground, is an abnormal condition.

I expect that the FAA will speak to the pilot about the offense of not occupying the pilot's seat with the engine running.
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Old 15th Oct 2019, 21:56
  #122 (permalink)  
Join Date: Jun 2002
Location: CEH2 (Black Diamond, Alberta)
Posts: 5,616
- Did the “pilot” even do a preflight?
- “Pilot” should have shut down prior to exit.

I'm guilty of forgetting to remove the chocks during my preflight. However, when I realized what was preventing me from moving, I did shut down prior to getting out and removing the chocks.

Most of my power-flying is on a gliding field where there are often people in relatively close proximity to the tow plane. I am always conscious of the potential need to quickly turn the mags off if anyone is approaching me.

However, I do have a lot of sympathy for the pilot. He has to live with the fact that his wife was severely injured because of his oversight/complacency.
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Old 18th Oct 2019, 04:15
  #123 (permalink)  
Join Date: Dec 2001
Location: FL, USA
Posts: 2,738
Everybody has forgotten chocks including me.
Its how you deal with an error or an oversight.
If anything this clearly shows that an accident is a chain of events and some accidents are years in the making (complacencies).

This was a rented airplane, they may have been delayed into a flight after sunset, renter may have been legal for night flight with passengers but not comfortable and so on.

Could have been many additional stress factors including the attitude/behavior of a passenger.
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Old 30th Oct 2019, 20:45
  #124 (permalink)  
Join Date: May 2004
Location: Bear Island
Posts: 570
The propeller arc is always live. Never EVER go there.
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Old 9th Jul 2020, 08:00
  #125 (permalink)  
Join Date: Oct 2018
Location: Mostly South of England
Posts: 875
It pains me to see some of the ads in the press for modular ATPL with grinning students in their crisp white pilot shirts, student epaulettes and a hand resting on the prop of a PA-28 or in this case a DA-40. Even if that thing hasn't even got an engine under the cowling and prop's a mock up - it's still promoting bad practise.
Here you go. In a popular monthly mag for a major ATO...

Auxtank is offline  
Old 10th Jul 2020, 08:07
  #126 (permalink)  
Join Date: Dec 2014
Location: LHBS
Posts: 247
Hey, it's because they are ATPL students, so in 2 years time they willl fly big jets, without remembering what a prop or magneto is
Just kidding of course, but I also watch thes photos, any many happy before / after sightseeing flight photos with the pilots and passengers touching blades, standing right next to blades etc.
While accidents rarely happen that way, it shows disrepspect to a literally lethal part of the aircraft, which WILL develop into complacency and if the circumstances are given, WILL directly lead to a prop accident.
Although not always fatal, aircraft propellers striking humans leave scars for life: missing fingers, amputated or totally paralized arm, very badly difigured face.
And of course you won't see THAT on social media or fancy brochures.
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Old 18th Aug 2020, 17:52
  #127 (permalink)  
Join Date: Jan 2004
Location: West Coast Canada
Posts: 4,082
The September Pilot has an article re mag checks. Personally I have a problem with the "dead' mag check. I always taught my students check the mags on shut down by going to 1200 rpm and then checking for a RPM drop with a left - both right -both and then mixture idle cut off. The reason for not turning both mags off with the engine running is that if the student isn't quick turning the mags back on, the engine will backfire and blow out all of the muffler baffles.

I was discussing this with an another instructor recently who strongly disagreed with me. My question to fellow ppruners is; has anyone ever seen a mag switch that would properly ground the mags when selected to left and right but leave a mag live when selected to off ?

Incidentally he did not know that the mag switch is designed so that the key can only be removed when the switch is in the off position. When I teach the shut down mag check I also tell the student to gently pull on the key when in the both, left and right position. On 2 occasions I have found switches that were worn enough that the key came off in the left position. It would be very easy to think you had turned the key all the way to the off position but instead left it in the left position with a mag live and the key out.

I also make a point of not wrapping your fingers around the blade if you have to reposition the prop to put in the tow bar.
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Old 19th Aug 2020, 11:37
  #128 (permalink)  
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Yes, I have seem several mag switches worn to the point where the key could be pulled out in any selected position, this mode of failure can be easily checked with the engine stopped. Yes!!! I have personally experienced (as the guy hand propping the plane) a mag switch, which when selected off, left the mags live. Happily, my habit of hand propping as though the mags were always live, and the engine could unexpectedly start, prevented an unhappy event that day. After the engine (C150) was wrongly running, and I glared at my trusted buddy in the cockpit - he replied with a surprised look, holding up the keys, which I could see through the running prop arc!

So, though I agree with BPF's observation about the risks to the exhaust of a careless live mag check, I always do these checks - with great care. I am certain to turn the key off only at the slowest possible idle RPM, and for the most brief period. Doing it that way, I've never had an exhaust backfire, but as BPF says, a live mag check conducted at power can certainly damage the exhaust. For those who would like a refresher; if the engine is turning, with the mixture rich, it's pumping fuel through. If it's running while it's turning, the fuel is obviously being burned - no problem. If you (during a successful live mag check) prevent the fuel being burned, it gets pumped through anyway. It'll accumulate in the exhaust after a few strokes, and may be reignited when the mags are turned on again. If the engine was turning fast, and the period of no ignition was many strokes, it'll pump quite a bit of fuel. That cold create a damaging backfire. This also applies in flight, if you must reduce power beyond throttle to idle, move the mixture to cut off, rather than turning the key off, if you intend to return the power in flight.

If the engine has turned over many strokes with the fuel on, and ignition off, if on the ground, it would be wise to let the engine stop, then sit for many minutes before restarting, so fuel may evaporate from the exhaust. If in flight, select the mixture to cut off, and let the engine windmill so as to blow through any fuel accumulated in the exhaust. You'll know you did it wrong if you hear a bang when you return ignition.

There is hardly any damage you could do to an exhaust system which won't be a few thousand dollars to repair. And, any exhaust work introduces the risk that a cylinder stud is damaged during removal, then you're having to change a cylinder as well, which will be many more thousands of dollars. So, it's worth not abusing the engine this way.
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Old 19th Aug 2020, 14:29
  #129 (permalink)  
Join Date: Jan 2004
Location: West Coast Canada
Posts: 4,082
Pilot DAR

I have seen a mag switch with a live mag when selected off but it also allowed a live mag when selected to the other mag and so would have been caught by my check. So my question is if the mag switch grounds the mag when individually selecting a mag but then allows a mag to live when in the off position. Has anyone seen that ?

I think that failure mode is essential impossible and so a running shut down check and the normal precautions around props are sufficient and therefore a full dead mag check where the mags are turned off with the engine running is not really required
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Old 19th Aug 2020, 17:02
  #130 (permalink)  
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I agree that if everyone always treated a stopped propeller as though it could start the engine if moved at all, live mag checks would serve little purpose, other than to confirm "airworthiness" of the mag switch itself. I also agree that the need to hand prop planes is happily becoming less, as non starter equipped planes become more rare. But there can always be reasonably legitimate reasons to pull a prop through by hand, like circulating engine oil after preheating, before starting, so with careful live mag check technique, I'd rather do the check, and have more (not total, more) assurance that the system is airworthy. I will still treat a prop as though it's live all the time.

'Story from the past:

In a past life, I was the O-200 key clutch repair guy, so all the clutches that cam into the engine shop for repair came to me. One of our customers, with a C 150, called back to say that the clutch we'd (I'd) just sent back repaired would not engage, and he was a bit fussed about this, wanting to go flying. I was told to fly down, and make it right. So, I packed up my tools, prepared to rebuild the clutch on site. It was possible I'd made an error, and it would not engage, so I was ready to make it right for the customer. I arrived to his plane after an hour flight, it was the one with the top cowl beside it on the grass. Sure enough, I turned the key, starter ran, prop didn't - problem. I asked the owner what had been done for installation. He replied that he had simply put the clutch back in, and had not fussed with anything else. So, I took the clutch out, and checked it, it seemed to be working correctly. I reinstalled it, and did some more checks, and everything seemed to be working correctly, I could feel it engage and disengage the starter motor with slight, and careful rotation of the prop. But still, the starter motor would not turn the prop. In diagnosing, it got to the point where I had the owner engage the starter, while I wiggled the prop with a bit of light rope, intended fly off the tip if the prop started to turn, it didn't. I was puzzled, and this was getting less safe to experiment with, as everything seemed to be working as it should. Then in desperation, I re-asked the question I'd already asked, just a little differently: "Are you sure that you haven't taken anything else apart here?". Then the reply (he knew I was really frustrated now); "Well... I did take the back plate off the starter motor to look inside...". The bugger had put it back on 90 degrees out of phase, and the starter motor was turning backward, of course my correctly repaired one way starter clutch would not engage! A quick fix, and the whole thing worked just fine. I could have saved an hour of frustration if I'd known to check the starter motor for misassembly. I must have looked like a fool wiggling a prop tip when the owner held the starter running!

It's worth understanding how your starter should work, and getting it fixed if it doesn't. And still, I support careful live mag checks....
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