Which way to turn a prop?
- Thread starter Mavmb
- Start date
flyguy
Well-Known Member
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The only problem with that method is that the distance you move the prop has nothing to do with the likelyhood of the engine starting. If you move it in the direction of normal rotation, you increase the risk that it will start. In the left magneto there is an impulse coupling that engages at low rpm. The impulse coupling is spring loaded and 'catches' as the engine rotates. It then springs forward, accelerating the magneto. By doing this it retards the timing and generates a hotter spark than would otherwise be possible at low rpm, increasing the chances of a start. If you turn the engine you will hear the impulse coupling 'click' as it releases. At higher rpm when the engine is running it disengages.
If you turn the engine the wrong way, the impulse coupling will not engage, making an accidental start unlikely.
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Good point, but I've already done a P-Lead grounding check and shut down the engine by fuel starvation. At this point I'm pretty sure its not going to start. The only reason I turn it in the direction where I can turn it the least and have it be out of the way is to keep from damaging components. I belive that someone said something about damaging the vacuum pumps. Stuff like that. Also, its less work for me. Props take a little elbow grease to turn by hand.
Although I will admit that an extra 6 inches won't matter either way, it just makes sense to be more efficient. Its like if you're heading north and want to turn to a heading of 185, it won't matter much which way you turn, but turning left makes more sense.
The only problem with that method is that the distance you move the prop has nothing to do with the likelyhood of the engine starting. If you move it in the direction of normal rotation, you increase the risk that it will start. In the left magneto there is an impulse coupling that engages at low rpm. The impulse coupling is spring loaded and 'catches' as the engine rotates. It then springs forward, accelerating the magneto. By doing this it retards the timing and generates a hotter spark than would otherwise be possible at low rpm, increasing the chances of a start. If you turn the engine you will hear the impulse coupling 'click' as it releases. At higher rpm when the engine is running it disengages.
If you turn the engine the wrong way, the impulse coupling will not engage, making an accidental start unlikely.
[/ QUOTE ]
Good point, but I've already done a P-Lead grounding check and shut down the engine by fuel starvation. At this point I'm pretty sure its not going to start. The only reason I turn it in the direction where I can turn it the least and have it be out of the way is to keep from damaging components. I belive that someone said something about damaging the vacuum pumps. Stuff like that. Also, its less work for me. Props take a little elbow grease to turn by hand.
Although I will admit that an extra 6 inches won't matter either way, it just makes sense to be more efficient. Its like if you're heading north and want to turn to a heading of 185, it won't matter much which way you turn, but turning left makes more sense.
DE727UPS
Well-Known Member
How about intentional hand propping?
Back in the day....you had to hand prop planes to get them to start cause they had no electrical system or battery. I've do this once in a while if I have a plane with a dead battery but don't think I'd want to do it on anything bigger than 150hp. I usually tie down the tail, chock the left main, set the parking brake, then make sure the throttle is slightly open, prime as necessary, mixure rich, fuel on, then prop away. I treat each throw like it could catch and start....step away as you reach the bottom of your motion. Don't stand too far back or you'll lose your balance in a forward direction when pulling your prop through...not good.
Bet they don't teach this at the big academies....nor would I teach it to a student unless they really wanted to learn but I think a CFI should know how to hand prop a plane and not be afraid of it.
Back in the day....you had to hand prop planes to get them to start cause they had no electrical system or battery. I've do this once in a while if I have a plane with a dead battery but don't think I'd want to do it on anything bigger than 150hp. I usually tie down the tail, chock the left main, set the parking brake, then make sure the throttle is slightly open, prime as necessary, mixure rich, fuel on, then prop away. I treat each throw like it could catch and start....step away as you reach the bottom of your motion. Don't stand too far back or you'll lose your balance in a forward direction when pulling your prop through...not good.
Bet they don't teach this at the big academies....nor would I teach it to a student unless they really wanted to learn but I think a CFI should know how to hand prop a plane and not be afraid of it.
pilot602
If specified, this will replace the title that
Re: How about intentional hand propping?
A guy with a 310 two spots down from us came over to me and asked if I had any ideas on how to start it with a dead battery.
I said he could prop it. For some reason he didn't go for that idea.
I don't think anyone would really want to try to prop a 310 but if one were able to get the prop spinning it would theoretically work.
A guy with a 310 two spots down from us came over to me and asked if I had any ideas on how to start it with a dead battery.
I said he could prop it. For some reason he didn't go for that idea.
I don't think anyone would really want to try to prop a 310 but if one were able to get the prop spinning it would theoretically work.
ready2fly
Well-Known Member
Re: How about intentional hand propping?
When I was about to take my Multi-Engine Instrument Rating, some jackass (read: me) had inadvertently left the Master on the day before, hence killing the battery.
The DE was trying to help me get the thing started the next day and he hand-propped the thing.
Don't think you'll ever see me doing that.
Don't want to end up as Ready2fly-curry.
But... to answer the thread:
I don't think it really matters, but if I ever have to turn the prop - which is rare - I turn it in the direction it normally spins.
R2F
When I was about to take my Multi-Engine Instrument Rating, some jackass (read: me) had inadvertently left the Master on the day before, hence killing the battery.
The DE was trying to help me get the thing started the next day and he hand-propped the thing.
Don't think you'll ever see me doing that.
Don't want to end up as Ready2fly-curry.
But... to answer the thread:
I don't think it really matters, but if I ever have to turn the prop - which is rare - I turn it in the direction it normally spins.
R2F
ananoman
New Member
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Only the left mag has it? Is that airplane-specific or universial?
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It is usually only in the left mag, but I am only familiar with Lycoming engines, so I am sure there are exceptions. Some older planes are started on the left mag only, then the right one is turned on after the engine starts.
Only the left mag has it? Is that airplane-specific or universial?
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It is usually only in the left mag, but I am only familiar with Lycoming engines, so I am sure there are exceptions. Some older planes are started on the left mag only, then the right one is turned on after the engine starts.
Alchemy
Well-Known Member
During training for Line Service Techs at the nation's largest chain FBO, I was told to turn the props clockwise as seen from the front of the plane (counterclockwise from the pilot's perspective, and opposite the engine-on direction of rotation).
I do it several times daily and my counterparts have done it thousands of times, never heard of anyone breaking a vacuum pump or having any other problem from it.
I do it several times daily and my counterparts have done it thousands of times, never heard of anyone breaking a vacuum pump or having any other problem from it.
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I have always been taught to rotate the prop backwards - and slowly!
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But if you're in the Southern Hemisphere shouldn't it rotate backwards anyway? Does that mean you should stand in front of the prop, on your head, and rotate it quickly with your feet???
I have always been taught to rotate the prop backwards - and slowly!
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But if you're in the Southern Hemisphere shouldn't it rotate backwards anyway? Does that mean you should stand in front of the prop, on your head, and rotate it quickly with your feet???
Michigan_Flyer
Well-Known Member
Where I work, we are required to turn the prop in the direction of normal rotation to reduce wear on the vacuum pump. I don't think that is the safest way though......
sixpack
New Member
Wow! A lot of discussion about what could happen if a prop was turned backwards 10 degrees or so.
Hmmmm. Seems like this happens quite often during shutdown... the engine rotates upto the compression point, and then backs off 10 to 20 degrees.
Hence, I don't think you'd be breaking any component of your airplane if you did this by hand.
(just my two cents... I think we're up to about $1.00 on this one
Hmmmm. Seems like this happens quite often during shutdown... the engine rotates upto the compression point, and then backs off 10 to 20 degrees.
Hence, I don't think you'd be breaking any component of your airplane if you did this by hand.
(just my two cents... I think we're up to about $1.00 on this one
B767Driver
New Member
Re: How about intentional hand propping?
[ QUOTE ]
Back in the day....you had to hand prop planes to get them to start cause they had no electrical system or battery. I've do this once in a while if I have a plane with a dead battery but don't think I'd want to do it on anything bigger than 150hp. I usually tie down the tail, chock the left main, set the parking brake, then make sure the throttle is slightly open, prime as necessary, mixure rich, fuel on, then prop away. I treat each throw like it could catch and start....step away as you reach the bottom of your motion. Don't stand too far back or you'll lose your balance in a forward direction when pulling your prop through...not good.
Bet they don't teach this at the big academies....nor would I teach it to a student unless they really wanted to learn but I think a CFI should know how to hand prop a plane and not be afraid of it.
[/ QUOTE ]
Don't forget to have a qualified pilot at the controls!
[ QUOTE ]
Back in the day....you had to hand prop planes to get them to start cause they had no electrical system or battery. I've do this once in a while if I have a plane with a dead battery but don't think I'd want to do it on anything bigger than 150hp. I usually tie down the tail, chock the left main, set the parking brake, then make sure the throttle is slightly open, prime as necessary, mixure rich, fuel on, then prop away. I treat each throw like it could catch and start....step away as you reach the bottom of your motion. Don't stand too far back or you'll lose your balance in a forward direction when pulling your prop through...not good.
Bet they don't teach this at the big academies....nor would I teach it to a student unless they really wanted to learn but I think a CFI should know how to hand prop a plane and not be afraid of it.
[/ QUOTE ]
Don't forget to have a qualified pilot at the controls!