Pulling the Prop through by Hand

Neither am I. Nor am I trying to catch you being wrong or anything. Just trying to understand this discussion best.

Certainly something I can stand to learn.

My logic here is given the understanding that the oil pump will really not pump oil until we actually get ignition - or close to there - I suspect that turning the prop by hand will cause the same wear/tear/friction OR less than that caused by the starter. The way I understand it when the start is engaged the oil pump is not doing much at those low RPM's.

Feel free to tell me I am completely wrong. There is always the very high probability I am.
 
This may help.....in the operators manual for small continentals....." Warm the engine up exceeding 700 rpm to assure oil flow to all parts of the engine. " also, when these engines sit for sometime, do not rotate engine by hand unless you intend to start it and fly it. Rotating it by hand simply scrapes oil off the cylinder walls leaving them prone to rust. The only reason radial engines are pulled thru several times before starting is to avoid hydraulic lock in the bottom cylinders which can ruin the engine. The only exception would be a radial with no elec. system. In that case you would also start it by pulling it thru. There is a video of a young fellow in the 70's doing just that while crop dusting in a Stearman 450.
 
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Yes I agree. From the information I have it is primarily for the purpose of avoiding hydraulic lock. I should've made that clearer in my post.
 
MAKG1 said:
50W isn't even close to SAE 50.

One is a high temperature spec, the other a low temperature spec. Even if the viscosity specs were the same (they aren't), 100 deg C temperature change is worth multiple orders of magnitude of difference.

The "W" stands for "winter," not "weight." It means the spec is done at 0 deg C, rather than at 100 deg C (meant to approximate operating temperature).

A multigrade -- like 15W-50 -- has viscosity specs at 0 deg C and at 100 deg C. It's an attempt to remove some of the temperature variation.
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thanks for the explanation. This whole time I thought it was.
 
denverpilot said:
And no one can give any proof it makes any difference in that either.
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I'm not aware of any proof that it works, and I'm not aware of any proof that it doesn't work. :dunno:

The battery will recharge. That's why we have batteries.
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That doesn't address the possibility of the battery not having enough juice in cold weather to get the engine started. If it's marginal, then I can see how it could make a difference.
 
Engine said:
Neither am I. Nor am I trying to catch you being wrong or anything. Just trying to understand this discussion best.

Certainly something I can stand to learn.

My logic here is given the understanding that the oil pump will really not pump oil until we actually get ignition - or close to there - I suspect that turning the prop by hand will cause the same wear/tear/friction OR less than that caused by the starter. The way I understand it when the start is engaged the oil pump is not doing much at those low RPM's.

Feel free to tell me I am completely wrong. There is always the very high probability I am.
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That would depend upon the wear condition of the oil pump and engine. My Warner would show oil pressure on the gauge when hand propped. The 0-300 in my 170 will do the same.
 
1600vw said:
This is why on hot rods we use a pre oiler. Starts oil flowing before you hit the key.

Tony
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And this is correct. The biggest wear occurs when you first start the engine, until the oil circulates. Hundreds of articles written about this.
 
Jimmy cooper said:
And this is correct. The biggest wear occurs when you first start the engine, until the oil circulates. Hundreds of articles written about this.
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Many aircraft have "Dry kits" that include a pre-oiler.

Operators run the pump after shut down to scavenge the sumps, to prevent hydraulic lock in radials, and run the pump as a pre-oiler prior to start.
 
Tom-D said:
The 0-300 in my 170 will do the same.
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Very true. When we were trying to start my 170 back in November when it was. 32F in Texas and the engine still had AeroShell 100 in it, I was showing 30 PSI on the gauge just from the starter turning it.....and we quickly drained the battery trying to start.
 
We must all realize there are some very big difference between engine makes and models.

The Flat engines with attached oil sumps don't require pre-oiling because the complete system is in the engine and when working as designed the system will stay full of oil, and start flowing as soon as the oil pump starts turning.

In dry sump engines this may or may not happen. It is more than likely that the system will not stay full of oil. When this happens the oil pump must re-prime the system before it can make pressure in the engine bearings.
 
Jimmy cooper said:
And this is correct. The biggest wear occurs when you first start the engine, until the oil circulates. Hundreds of articles written about this.
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How much does it matter? We have been starting engines without pre oilers for many many years in not so great environments.
 
flyingmoose said:
How much does it matter? We have been starting engines without pre oilers for many many years in not so great environments.
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I've had to fly light sport the past 7 years. It matters to me as these little continental engines, 65-85 hp are over 60years old! Rebuilt twice or so and maybe at the end of their run. I want to be able to sell each one without doing a rebuild or having to scrounge another engine. I really baby them for this reason without going to a lot of trouble. I always have a spin on filter, change oil every 25 hours, warm them up first if under 35 degrees and so far it's worked. Have not been stuck with any and have broken even so far. I've never used a pre oiler, I doubt many have. Knowing who your buying from helps too!
 
I am the pre-oiler. Yes - I do in fact, have a dry sump engine.
 
I have noticed while pulling my right prop backward, it makes a noise I don't like; like a protesting pump. I am now thinking that is the vacuum pump. The left engine does not do it. I guess I will be watching the right vacuum pump closely.
I am not in the habit of pulling the props through in cold weather and these engines (O-470) are a B**ch to start when cold. I am going to try pulling them through a few times the next time I take her out in the cold air!
 
Anyone know how Tom is doing ? This is a really old thread.
 
FastEddieB said:
Does not priming also tend to wash off residual oil in the cylinder?

May or may not, but I have that impression.

BTW, how is it that our cars and motorcycles, even the air cooled ones, all seem to get along fine without being "pulled through"?
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Take note of how many turns prior to start in your car, or motorcycle. I want my airplane to fire and run after 1 or 2 compression strokes.
Also, side draft, and down draft induction, vs up draft in most airplanes. Plus hotter spark on most land based vehicles.
The cold starting ritual of my old motorcycle requires about ten pumps of the throttle, and ease it through with the kicker about 4 rounds, turn the switch on, and come down hard on the kicker. it fires right up. Very similar to the older technology of our aircraft engines. more so, than an automobile built after about 1973.
 
Before pulling a prop through the aircraft needs to be tied down or someone at the controls and on the brakes. Chocks are not enough.
 
My safety practice for hand propping is to prime and pull mixture to lean cutoff. When it fires I have about 2 seconds to get to the controls before it quits. When off airport there’s no tying it down. When pulling a prop through ahead of a cold start the mixture is still in idle cutoff from the last shutdown so start potential is near zero. I’m still careful but not scared.
 
Lycoming / Continental: Pulling through backwards - snot a big deal, but generally not much point unless you feel the need to re-position the prop... You aren't going to pull any fuel into the cylinders, you aren't going to "loosen up" the oil. Fine if you are positioning a cylinder at TDC, but if you have at least one set of plugs out - spin away.
Pulling forward - one needs to be careful and take precautions appropriate to the reason you are pulling forward. Flipping the prop to "clear" a flooded engine with the throttle wide open? There are holes in the hangar door next to mine.

Rotax: Pulling through backwards - never. Not no way, not no how (at least beyond a couple degrees). Air in the lifters can lead to valve damage (at least according to the factory).
Pulling forward - no big whoop if you pull at a reasonable speed. Ain't no impulse, she ain't a gonna fire. But, there is no reason to have the fuel / mags on if you are just burping the crankcase (which is a regular event). On the other hand, there is no need for someone at the controls or to have it tied down.
You can prop it to start, but it takes a good snap on the prop. For that you want it at least tied down, particularly since most Rotax have the carburetors spring loaded to open.
 
If you have a really low battery pulling he prop back to just after compression can help the engine get a running start before it has to overcome the compression.
 
IF just trying to break static friction, then you only need to move it slightly, no need to pull it through a complete rotation.


Tom
 
mwagg737 said:
I have noticed while pulling my right prop backward, it makes a noise I don't like; like a protesting pump. I am now thinking that is the vacuum pump.
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Protesting pump? Even if you spun the thing backwards at engine speed it probably wouldn't make a noise. I suspect something else on your accessory case is protesting (or you've got a valve issue).
 
On old Lycomings, Franklins and Continentals (without starters) you prime them, then pull them through 6(ish) times to get fuel into the cylinders. BTW: A bunch of them don't have primers.
Many of those engines don't have accelerator pumps on the carbs so moving the throttle back and forth does nothing. You crack the throttle so you can suck some fuel into the engine when you prop it.
If fuel comes out the exhaust, it's flooded. You shut off the fuel, then prop them backwards until your arms fall off, to clear the fuel out of them, then start over.
 
Especially on twins!
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