I learned to fly in 1955 and my old instructor taught me to turn the prop by hand 6 times before start up. His reason: to get oil up into the cylinders.
Today the mechanics laugh at me and say I could never turn the prop fast enougth to do this.
Their theory: when prop is turned by hand this pulls oil down out of the cylinders leaving them dry, which in turn could damage the engine when starter is engaged.
I am still turning the prop by hand 6 times before engine start up on my 1951 Cessna 170A.
This should get all the dogs to barking
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Bruce Fenstermacher
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Re: This should get all the dogs to barking
Arf arf arf.
You'll never get oil pressure or splash oil in the cylinders of course. Your starter probably can make oil pressure or splash much oil in six rpm either.
This is probably a left over necessity from the days when everyone was flying radial engines and the bottom cylinders had to be cleared before start.
I've turned props over a few blades when OAT is really cold to "loosen" up the engine. Probably makes not difference but I felt better.
You'll never get oil pressure or splash oil in the cylinders of course. Your starter probably can make oil pressure or splash much oil in six rpm either.
This is probably a left over necessity from the days when everyone was flying radial engines and the bottom cylinders had to be cleared before start.
I've turned props over a few blades when OAT is really cold to "loosen" up the engine. Probably makes not difference but I felt better.
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Re: This should get all the dogs to barking
I was taught the same thing in a Champ. Pulled the prop through 6 times with mags off and it always started on the first pull with mags on. If the engine was warm, I was taught that if you looked at it, it would flood on a warm start. Since that happened alot, I was taught to back prop it 11 times (mags off) to clear the carb. I always tied that bird down for every start and never opened the throttle more than a crack. I was taught that you always position yourself in the pattern to be within gliding distance of the runway in case the engine quit and every landing started by pulling the throttle to idle abeam the numbers and making a power off approach. Now days, if you try that you will get run over by someone making the usual 747 approach. I am glad I have a 1950 170A and still can get to fly it. I don't miss hand propping. 
Re: This should get all the dogs to barking
I couldn't agree more! These pilots that drag the downwinds out for no real reason should think about their actions!voorheesh wrote: I was taught that you always position yourself in the pattern to be within gliding distance of the runway in case the engine quit and every landing started by pulling the throttle to idle abeam the numbers and making a power off approach. Now days, if you try that you will get run over by someone making the usual 747 approach. I am glad I have a 1950 170A and still can get to fly it. I don't miss hand propping.
Low and slow are the major ingrediants of disaster.
Joe Craig
'56 C172 Taildragger N6915A
'46 Aeronca Champ N65HM
'56 C172 Taildragger N6915A
'46 Aeronca Champ N65HM
Re: This should get all the dogs to barking
Pulling the prop through all six compression strokes will give you an idea of compression, and can expose a stuck, or otherwise leaking, valve.
For us, it exposed an exhaust valve in the early stages of sticking. It wouldn't stick when running, but would stick when shut down. A little reaming with a proper ream, and all was well thereafter.
On another occasion, one cylinder felt a little weaker than the rest, and we could hear it leaking into the exhaust. A bore scope revealed a corroded valve face, and early erosion. Pulled the cylinder, ground and lapped the valve and seat, reinstalled. All was well, as we caught it before it became expensive.
We are believers in pulling the prop through before the first start of the day.
For us, it exposed an exhaust valve in the early stages of sticking. It wouldn't stick when running, but would stick when shut down. A little reaming with a proper ream, and all was well thereafter.
On another occasion, one cylinder felt a little weaker than the rest, and we could hear it leaking into the exhaust. A bore scope revealed a corroded valve face, and early erosion. Pulled the cylinder, ground and lapped the valve and seat, reinstalled. All was well, as we caught it before it became expensive.
We are believers in pulling the prop through before the first start of the day.
Re: This should get all the dogs to barking
For horizontally-opposed engines:
Pulling a prop thru to detect an unhealthy engine is a completely different purpose than for preparing an engine for start.
Pulling a prop thru to "pre-lubricate" an engine is mostly imaginary. (The starter does the same thing...and does it a lot safer in case of an undetected "hot" mag.)
Pulling a prop thru to "free" it up in cold weather may have some value if thick oil and no preheat is available....but a starter will also do the same thing if you have a good battery, and if you don't then use a ground power unit. What? You don't have a ground power plug installed? Get one!
In cold wx, pulling thru also helps prime the engine with fuel/air if you've used your primer.
A hot engine that tends to flood easily, if pulled backwards, will indeed help clear the cylinders. But a better method in my view is to crank it with the starter and with the mixture in idle cut-off. Do NOT PUMP the throttle, of course or you will inject fuel with the accelerator pump. Another reason NOT to turn an engine backwards is... if you have a dry vacuum pump with carbon vanes...you likely just injured it, and you did your generator brushes no good either. You may also contribute to loss of oil pump prime.
Summary, use the starter. The sooner you can get that engine to start (with the fewest revolutions...including manual revolutions) .... the better....and the sooner real oil pressure will be available to lubricate upper cylinders and cams and other bearings.
Pulling a prop thru to detect an unhealthy engine is a completely different purpose than for preparing an engine for start.
Pulling a prop thru to "pre-lubricate" an engine is mostly imaginary. (The starter does the same thing...and does it a lot safer in case of an undetected "hot" mag.)
Pulling a prop thru to "free" it up in cold weather may have some value if thick oil and no preheat is available....but a starter will also do the same thing if you have a good battery, and if you don't then use a ground power unit. What? You don't have a ground power plug installed? Get one!
In cold wx, pulling thru also helps prime the engine with fuel/air if you've used your primer.
A hot engine that tends to flood easily, if pulled backwards, will indeed help clear the cylinders. But a better method in my view is to crank it with the starter and with the mixture in idle cut-off. Do NOT PUMP the throttle, of course or you will inject fuel with the accelerator pump. Another reason NOT to turn an engine backwards is... if you have a dry vacuum pump with carbon vanes...you likely just injured it, and you did your generator brushes no good either. You may also contribute to loss of oil pump prime.
Summary, use the starter. The sooner you can get that engine to start (with the fewest revolutions...including manual revolutions) .... the better....and the sooner real oil pressure will be available to lubricate upper cylinders and cams and other bearings.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
Re: This should get all the dogs to barking
I agree George. I don't pull my prop through or back prop it anymore. This thread brought back memories of this old instructor I used to have who had very strong opinions on stuff like this and didn't hesitate to make new guys believers. He never did really explain any of it but he sure let you know his version of the "right way". I flew with him in a 7AC with no electrical system and instruction was by yelling and hand signals from behind. Sure was fun back then.