Guy hit and killed by prop

The place I rent from (172's) has us check everytime we shut down. After flipping the avionics master off, and at idle, click the key to left, then right, then for a split sec to off then back to both too see that it kills the motor. Since the key switch kills the mags by grounding, the idea is if the the ground wire broke inflight, you would find out now. Then we do a normal shut down by pulling the mixture.
 
I was always under the impression that you could inavertly hand prop start accidentally by turning it in the right direction.. a lot of things I think have to go wrong to do it but one in a million is still a dead guy laying on the ground. I always move prop a few inches in opposite direction After inspecting it. I’m sure that is not perfect and probably there is going to be some PoA ribbing for how that’s wrong but I’m open to other suggestions.
I’m guessing the this guy just grabbed prob while looking in the opening on the right side pushed the prop down and it just turned over and whack. Really sucks.
 
benyflyguy said:
I was always under the impression that you could inavertly hand prop start accidentally by turning it in the right direction.. a lot of things I think have to go wrong to do it but one in a million is still a dead guy laying on the ground. I always move prop a few inches in opposite direction After inspecting it. I’m sure that is not perfect and probably there is going to be some PoA ribbing for how that’s wrong but I’m open to other suggestions.
I’m guessing the this guy just grabbed prob while looking in the opening on the right side pushed the prop down and it just turned over and whack. Really sucks.
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There might be some truth in that. One of my old CFI’s would always turn the prop the opposite direction of its powered rotation. I know there’s some engines that aren’t supposed to be turned opposite direction (Rotax?)

Glad you brought this up, because it reminded me of that. Someone else can shed some light on it.
 
overdrive148 said:
Always treat the prop like a loaded gun.
Do not touch the prop unless absolutely necessary.
Never reach through the prop arc for anything.
Only touch the prop with a flat hand.
(Line service tech experience)
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Great list! I will just add that if you MUST turn the prop (to get a towbar under it etc.) to rotate the propeller *backwards*

*I had a CFI a long time ago "clear" the throttle during shutdown after the mixture was brought to full lean by sweeping the throttle full open then full closed.
 
Hi.
Always stay behind and as far as you can from the prop.
Never have more than your finger tips on it.
Turning against the normal direction of rotation can damage some engines, and it can still start in some acft.
 
Tantalum said:
Great list! I will just add that if you MUST turn the prop (to get a towbar under it etc.) to rotate the propeller *backwards*
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Can the mags fire if it’s rotated backwards?
 
Ryanb said:
Can the mags fire if it’s rotated backwards?
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The explanation I was given is that when you cycle it backwards it's pulling in air from the exhaust manifold, so it's less likely to have a combustible charge in it. That's a good question about mags firing backwards though, I believe it has to do with whether it has an impulse coupling or not. I am sure @Ted DuPuis knows!

Mind you, that's not fool proof either, I've first hand seen people when trying to start an engine have it run backwards for a second or two. Typically when they've overprimed and flooded the crap out out of it and let off the starter at just the right moment it will kick backwards and do a few rotations in reverse. I want to say many moons ago someone, maybe 6PC, had a thread about running a plane engine backwards
 
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Turning the prop backwards can be dangerous as it can still build up enough compression to spring it back forward. A friend's dad learned that lesson the hard way when I was a kid.

It can also damage vacuum pumps, as the vanes in some pumps are only designed to turn forwards.

The best method is to never turn the prop unless you have to, and treat it like it could catch if you do have to move it. One of our club planes tends to stop with the prop vertical, making it impossible to use the tow bar. When I'm being mindful, I put the towbar down to move the prop forward the way I would do it if I were hand-starting. I'll admit that I'm not always that mindful.
 
Eric Gleason said:
The best method is to never turn the prop unless you have to, and treat it like it could catch if you do have to move it. One of our club planes tends to stop with the prop vertical, making it impossible to use the tow bar. When I'm being mindful, I put the towbar down to move the prop forward the way I would do it if I were hand-starting. I'll admit that I'm not always that mindful.
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EDIT: I learned how to read and see you move it forwards..

**honestly, what worries me more, is I've seen people TRY to start a plane, not have any success, then go and scrub the flight and disappear. Now you have a plane sitting on the ramp with an intake manifold full of combustible compounds.. so I've been always partial to turn it backwards if I MUST move it, that exhaust manifold thing a CFI told me once made sense. I'd rather shave a few hours off the vac pump than shave off my scalp

Mind you I'm not married to either!

**and again.. thank you WW2 engine technology. Imagine if you had to be careful loading grocery in your car, for leaning on the bumper and moving it forward a quarter inch may cause it to spring to life and run you over? JFC
 
Signage at an Air Force base, from my youth:

"If you never walk through a prop arc, you'll never get hit by a prop"

For guys not used to being at bases with prop aircraft, I think. It can be a tough rule to follow when attaching a tow bar to a 172.
 
Eric Gleason said:
I'll admit that I'm not always that mindful.
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Don’t feel bad. I’m not always mindful either. It’s sad that things like these have to happen for us to start thinking about it.
 
G-force said:
The place I rent from (172's) has us check everytime we shut down. After flipping the avionics master off, and at idle, click the key to left, then right, then for a split sec to off then back to both too see that it kills the motor. Since the key switch kills the mags by grounding, the idea is if the the ground wire broke inflight, you would find out now. Then we do a normal shut down by pulling the mixture.
Click to expand...

This is what I was taught to do as well.
 
Eric Gleason said:
Turning the prop backwards can be dangerous as it can still build up enough compression to spring it back forward. A friend's dad learned that lesson the hard way when I was a kid.

It can also damage vacuum pumps, as the vanes in some pumps are only designed to turn forwards.

The best method is to never turn the prop unless you have to, and treat it like it could catch if you do have to move it. One of our club planes tends to stop with the prop vertical, making it impossible to use the tow bar. When I'm being mindful, I put the towbar down to move the prop forward the way I would do it if I were hand-starting. I'll admit that I'm not always that mindful.
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99% of the time my prop will stop vertical, in fact i dont even remember seeing stop horizontally... donno why, so i have to move the prop by hand, and i do it backwards.. may be i should rethink
 
Ryanb said:
Can the mags fire if it’s rotated backwards?
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Absolutely NOT. The first thing is the impulse coupling does not work in reverse, the second thing is the points open at the wrong time to have a field coil energized to fire the plug.
 
overdrive148 said:
Always treat the prop like a loaded gun.
Do not touch the prop unless absolutely necessary.
Never reach through the prop arc for anything.
Only touch the prop with a flat hand.
(Line service tech experience)
Click to expand...
BS propagated by those who believe old wives tales.
 
Tom-D said:
Absolutely NOT. The first thing is the impulse coupling does not work in reverse, the second thing is the points open at the wrong time to have a field coil energized to fire the plug.
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Thanks Tom for coming along with some inside knowledge. So the times that people "run" a GA piston engine backwards for a few turns.. is the engine just "dieseling" in essence? Or is what we are seeing and hearing something else?
 
Tantalum said:
Great list! I will just add that if you MUST turn the prop (to get a towbar under it etc.) to rotate the propeller *backwards*
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Finally, some one is getting it.

If you can get an engine to fire going in reverse, you could get it to run in reverse.
 
A
Ryanb said:
There might be some truth in that. One of my old CFI’s would always turn the prop the opposite direction of its powered rotation. I know there’s some engines that aren’t supposed to be turned opposite direction (Rotax?)

Glad you brought this up, because it reminded me of that. Someone else can shed some light on it.
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Can screw up vacuum pump. They don’t like going backwards.
 
Tantalum said:
Thanks Tom for coming along with some inside knowledge. So the times that people "run" a GA piston engine backwards for a few turns.. is the engine just "dieseling" in essence? Or is what we are seeing and hearing something else?
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Most time when that happens, it's just a kick back on a starter.
 
Paulie said:
A

Can screw up vacuum pump. They don’t like going backwards.
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NO it can't another misconception. when you rotate a vac-pump backwards it pushes the vanes into the rotator and clear of the housing.
 
Tom-D said:
NO it can't another misconception. when you rotate a vac-pump backwards it pushes the vanes into the rotator and clear of the housing.
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The one I just installed had a warning not to turn in wrong direction. What pushes the vanes? They contact something. Jeez don’t you have anything better to do or are you striving for 30,000 posts?
 
haha @Paulie I was curious about the vacuum pump thing since in my mind's eye I was picturing a marine style impeller.. but at least if what I'm seeing is accurate the vanes just go in and out based on centrifugal force <- mind you that video kind of sucks but if you look at cutaways on Google it makes sense. There were a few I saw that were angled a certain way.. but if anything that angle would push the vanes into the shaft as it got into the narrow part of the cylinder

Who knows. I will say that I'd much rather spin a prop a half turn backwards than forwards. Never flown anything with a Rotax though.. maybe that's a whole different beast!
 
Paulie said:
The one I just installed had a warning not to turn in wrong direction. What pushes the vanes? They contact something. Jeez don’t you have anything better to do or are you striving for 30,000 posts?
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30,000 posts will happen but it is not my goal.
what pushes the vanes? centrifugal force, just like it was being driven in the correct direction. they contact the housing with more force when being driven in the correct direction than they will being driven in the reverse direction.

The warning on your pump is just a CYA for the company.
 
OBTW Paulie, there is nothing I rather do than squelch BS on the page, And to stop old wives tales that no longer have merit, because they were based on technology your grandfather thought was old.
 
**here's a stupid question while we're on the topic of vacuum. How did vacuum become the standard? Seems like it would make more sense to use positive pressure to feed air driven instruments like a DG, etc. I would think a positive pressure system is far easier to construct and maintain..? there must be a reason, but it is not obvious
 
Tantalum said:
**here's a stupid question while we're on the topic of vacuum. How did vacuum become the standard? Seems like it would make more sense to use positive pressure to feed air driven instruments like a DG, etc. I would think a positive pressure system is far easier to construct and maintain..? there must be a reason, but it is not obvious
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Carry on from Venturi's
just a better method of doing it.
 
With a hot engine, is master off, ignition off, enough to prevent an inadvertent start when you want to rotate the prop horizontal?

I’m guessing no?
 
woodchucker said:
With a hot engine, is master off, ignition off, enough to prevent an inadvertent start when you want to rotate the prop horizontal?

I’m guessing no?
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Not if the ground wire to your magnetos is broken. If the wires are good, with Master and ignition off, the engine won't run.
 
Thanks. That’s what I thought.

Is there a link maybe I can read up on this? Where I did my private the checklist included the ignition to off then back to both to verify the electrical was good. I never fully understood the reasoning. When a million things are important some get left unexplained. I could use a good remedial education here. Thanks in advance
 
If you don’t get a drop when performing the mag check during the run up, you likely have a broken ground wire and a hot mag even with the key removed. The mag check is to ensure each mag (and associated components) are working properly, AND to detect a hot mag.

I’ll bet there are more than a few pilots that would not catch this problem during the run up. I wonder if the deceased pilot missed this during his preflight. Of course the ground wire may have just broken during incident flight.
 
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Every time I move the prop I hear my old man saying, 'careful there could be a hot mag'. Like others have said, my prop stops vertical as well more often than not. When I move the prop to use the tow bar I rotate it slowly in the opposite direction
 
Tom-D said:
Carry on from Venturi's
just a better method of doing it.
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How so? What drives the instruments is pressure differential. You can make that differential either by reducing the pressure on the outlet side (venturi or vacuum pump) or increasing it on the inlet side. I think the Beech Baron, Bonanza, and Piper Navajo use pressure systems instead of vacuum.
 
Tom-D said:
OBTW Paulie, there is nothing I rather do than squelch BS on the page, And to stop old wives tales that no longer have merit, because they were based on technology your grandfather thought was old.
Click to expand...
Calls ammonia an acid: https://www.pilotsofamerica.com/community/threads/paint-stripping.101772/#post-2244913
Claims water isn't a solvent here: https://www.pilotsofamerica.com/community/threads/corrosion-treatment.102604/
Came up with his own term of "jellied acetone" and claimed it was a paint stripper: https://www.pilotsofamerica.com/community/threads/chemical-strippers.101866/#post-2249982
 
Cap'n Jack said:
How so? What drives the instruments is pressure differential. You can make that differential either by reducing the pressure on the outlet side (venturi or vacuum pump) or increasing it on the inlet side.
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You are correct. But using a venturi in the slipstream is cheap and reliable. (NB does't work in icing conditions.)

The alternative (a funnel-like ram air device) would be less effective, particularly at low speeds. To get 5psi you would need a large air funnel = drag.

Aviation designers like low drag, cheap, and reliable.

-Skip
 
G-force said:
The place I rent from (172's) has us check everytime we shut down. After flipping the avionics master off, and at idle, click the key to left, then right, then for a split sec to off then back to both too see that it kills the motor. Since the key switch kills the mags by grounding, the idea is if the the ground wire broke inflight, you would find out now. Then we do a normal shut down by pulling the mixture.
Click to expand...

I always do a mag ground check before shutting down, it was ingrained by my old crusty musty primary CFI.
 
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