Rotating Prop by hand during periods of inactivity

[Roscoe]

I watched an EAA Webinar a couple of days ago and asked a question about the practice of pulling the Prop through a few revolutions to move the oil around if the Aircraft had been idle for a few weeks.

I quote part of his reply and  am interested to hear what you think.

IT ACTUALLY MAKES THINGS  WORSE BY ACCELERATING THE MIGRATION OF OIL FROM THE TOP OF THE CYLINDER TO THE BOTTOM.

WHEN CYLINDERS DEVELOP RUST PITTING, IT TENDS TO BE MOSTLY ALONG THE TOP BECAUSE THATS WHERE THE OIL FILM IS LOST FIRST.

I know its far better to fly the Aircraft and get the oil up to operating temp.

Any comments?

 

 

[skippydiesel]

I think it is good practice to rotate the prop slowly through a number of compressions (I would suggest a minimum of 2 rotations of the engine). This is not just to pre-lubricate (valuable) it also helps the pilot assess evenness of compression as a measure of engine "health".

 

In Rotax 912/914 engines it is a recommended pre first  flight action of the day, to to relocate any "pooled" oil from the crankcase back to the reservoir (the famous "gurgle"). 

 

If the engine is being used very infrequently, your advisers observations may have some validity. In this case proper "mothballing" of the engine should be considered (see your POH).

 

If it were possible I would pre lubricate every engine befor the first start of the day - in the past heavy machinery did this with the use of a "pilot" motor to bring oil/fuel pressures up to minimum operating, befor the main "donk" kicked in.

[Roscoe]

10 minutes ago, skippydiesel said:

I think it is good practice to rotate the prop slowly through a number of compressions (I would suggest a minimum of 2 rotations of the engine). This is not just to pre-lubricate (valuable) it also helps the pilot assess evenness of compression as a measure of engine "health".

 

In Rotax 912/914 engines it is a recommended pre first  flight action of the day, to to relocate any "pooled" oil from the crankcase back to the reservoir (the famous "gurgle"). 

 

If the engine is being used very infrequently, your advisers observations may have some validity. In this case proper "mothballing" of the engine should be considered (see your POH).

 

If it were possible I would pre lubricate every engine befor the first start of the day - in the past heavy machinery did this with the use of a "pilot" motor to bring oil/fuel pressures up to minimum operating, befor the main "donk" kicked in.

Yes I am aware of the compression check which i do before every flight. The EAA Presenter was in the USA and probably referring to Cold weather and Pilots pulling thru their Engines once a week to scatter the oil around.

[skippydiesel]

1 minute ago, Roscoe said:

Yes I am aware of the compression check which i do before every flight. The EAA Presenter was in the USA and probably referring to Cold weather and Pilots pulling thru their Engines once a week to scatter the oil around.

The presenter may have a point in that sort of situation - that's why I suggested a proper "moth ball" procedure (some people call it "pickling" the engine as in preserving). I dont know a great deal about it but have found out that special lubricants, treated membranes, dehumidifiers, and plugs seem to figure highly. Many of the suppliers of these products are focused on military applications (engines of all sorts in "hibernation"). 

[lee-wave]

My flying is fairly infrequent so I am trying this procedure on the hydraulic lifter Jab motor.   

 

At the end of the flight fuel cock off,    allow the motor to run out of fuel and shut down.   All electrics off.  Rotate the prop through a couple of times.  The thoughts there are oil has not drained or been washed away by the fuel, is less viscous so will readily coat all surfaces.

Before the next flight rotate prop as normal. It is important for me to feel good compressions on all 4 cylinders.

Then I press the starter for 5 seconds without the ignition on.  Then fuel cock open, 10 seconds on the fuel pump to refill the carb. 

After that choke fully out, throttle completely closed (engine will be harder to start if idle is set too high). Engine always starts instantly.  Do not touch the choke or throttle for at least 20 seconds.  Thereafter everything as normal.

Any comments on these procedures...?

[Old Koreelah]

That’s pretty much what I do, except for running it dry of fuel. I almost never turn off my fuel and don’t have a problem with AvGas in the bowl for months. 
I presume you let the engine cool down before you turn it with the prop. I’m always wary of a hot glowing bit of AvGas deposit causing it to fire.

[lee-wave]

For sure I let it cool down before rotating prop.  There are schools of thought re leaving a dry carb bowl for long periods of disuse. Do the 'o rings /seals dry out and become brittle etc... but from the UK Jab motor guru (my brother) for the past 25 years of Jab motor repairs he has not seen any problems with wet or dry carb bowls.

As an aside I use Esso 97 synergy mogas during the summer.  It is the only fuel guaranteed not to have any methanol additives.  

Toward winter, like now, I start filling with Avgas, so that there is mostly Avgas during Dec/Jan in the wing tanks. 

So far I have not done a full inhibit on the Jab because, on my mainly chalk strip on the north downs,  the drainage is very good and there is always the opportunity to fly at least once a fortnight....

Probably discussed before but what are your thoughts re flring up the motor for ground runs every now and then...? 

[Roscoe]

4 minutes ago, lee-wave said:

For sure I let it cool down before rotating prop.  There are schools of thought re leaving a dry carb bowl for long periods of disuse. Do the 'o rings /seals dry out and become brittle etc... but from the UK Jab motor guru (my brother) for the past 25 years of Jab motor repairs he has not seen any problems with wet or dry carb bowls.

As an aside I use Esso 97 synergy mogas during the summer.  It is the only fuel guaranteed not to have any methanol additives.  

Toward winter, like now, I start filling with Avgas, so that there is mostly Avgas during Dec/Jan in the wing tanks. 

So far I have not done a full inhibit on the Jab because, on my mainly chalk strip on the north downs,  the drainage is very good and there is always the opportunity to fly at least once a fortnight....

Probably discussed before but what are your thoughts re flring up the motor for ground runs every now and then...? 

The EAA Presenter said their is absolutely no value in a ground run unless the oil temp is brought up to operating level and kept their for a while to dissipate any moisture and or sludge

[Roscoe]

1 hour ago, lee-wave said:

My flying is fairly infrequent so I am trying this procedure on the hydraulic lifter Jab motor.   

 

At the end of the flight fuel cock off,    allow the motor to run out of fuel and shut down.   All electrics off.  Rotate the prop through a couple of times.  The thoughts there are oil has not drained or been washed away by the fuel, is less viscous so will readily coat all surfaces.

Before the next flight rotate prop as normal. It is important for me to feel good compressions on all 4 cylinders.

Then I press the starter for 5 seconds without the ignition on.  Then fuel cock open, 10 seconds on the fuel pump to refill the carb. 

After that choke fully out, throttle completely closed (engine will be harder to start if idle is set too high). Engine always starts instantly.  Do not touch the choke or throttle for at least 20 seconds.  Thereafter everything as normal.

Any comments on these procedures...?

I find that the normal Jab start procedure per the POH works fine for

me.

However unless i slowly push the choke in immediately after the engine starts, it runs rough but smooths out as soon as the choke is in

[Old Koreelah]

33 minutes ago, lee-wave said:

 

Probably discussed before but what are your thoughts re flring up the motor for ground runs every now and then...? 

As Roscoe says, ground runs might do more damage than good unless you get the oil properly heated. That takes quite a while in cooler weather and you risk overheating the heads. My solution is a few fast taxi runs along the strip, keeping revs down until the engine warms up. The air flow quickly equalizes CHTs and you get some useful low level trading into the bargain.

[kgwilson]

I tend to agree that pulling an engine through a few times say once a week during a cold damp winter when there is no flying is going to do the engine more harm than good. It isn't going to move oil around much at all but it is going to suck moisture laden air into the cylinders which will do nothing except promote corrosion. If you decide that you are unlikely to go flying for weeks or months a squirt of inhibitor in each cylinder & a few rotations to distribute it is best. But you also need to block the intake and exhaust to stop moisture laden air sneaking in.

 

This isn't a problem where I live and I fly throughout the year though we do get very high diurnal temperature and humidity changes so the most effective protection is blocking air intake and exhaust orifices. I do this every time I put the plane to bed even when I am away from home along with the other 8 "remove before flight" covers.

[skippydiesel]

I am not so keen on the "inhibiter" being squirted into "each cylinder" where does it go? Whats its qualities? Past the rings contaminating/changing the crankcase oil? 

Floods advised x 1/month, a squirt of engine oil into each cylinder, rotate engine x 2, put plugs back in (be sure to put a rag over each plug hole, to catch surplus oil squirting out).

[facthunter]

Re running it now and again. IF it doesn't get fully warm each time I wouldn't do it. To stabilise your engines temp can require 45 minutes flight Turning it over by hand won't fling oil anywhere. Turning it for a while might prime the bearings and lifters but not things like a high located camshaft.. the most likely places for corrosion are the cam lobes exhaust stems and bore upper areas and the rings.. There's very little oil left after the oil rings scrape it off.

  It's commonly agreed the most rapid wear is after start up but I don't think that equates with pulling it through by hand. I'd do that say once a month and spray a storage oil in each cylinder with it's piston at bottom dead centre. The WORST thing to do is leave your plane near the clubhouse, then later in the day taxi it a few hundred meters to the hangar  and not use it for a few months.. Nev

[Yenn]

I wold say never turn the engine unless you intend to start it. All you are doing is wiping the oil off the camshaft and everywhere else.

If you are going to start it, then turn it over to check compressions and to see that it is not stuck.

If it has been a while since starting and you are not going to get the temps up high enough to get rid of water in the oil, I would not say don't do it because the temps are too low. I would say do it to get fresh oil around the system and even do it regularly, but only getting high temps will boil off moisture. I consider it better to splash a bit of oil around rather than leave it to slowly break down on the bearing surfaces.

Best to fly regularly, but if you can't, then run it as often as possible.

[skippydiesel]

1 hour ago, Yenn said:

I wold say never turn the engine unless you intend to start it. All you are doing is wiping the oil off the camshaft and everywhere else.

If you are going to start it, then turn it over to check compressions and to see that it is not stuck.

If it has been a while since starting and you are not going to get the temps up high enough to get rid of water in the oil, I would not say don't do it because the temps are too low. I would say do it to get fresh oil around the system and even do it regularly, but only getting high temps will boil off moisture. I consider it better to splash a bit of oil around rather than leave it to slowly break down on the bearing surfaces.

Best to fly regularly, but if you can't, then run it as often as possible.

Hi Yenn - your advice sounds a little contradictory.

 

In my case my Rotax 912 is temporarily out of the aircraft.

 

Regarding preservation best practice, I did a bit of reserch, which pretty much confused the hell out of me ,required quite a few different chemicals, dehumidifiers, membranes , plugs  etc (& a lot of the materials only came in large quantities) all very costly.

 

Emailed Wal at Floods:- he recommended filling the engine with clean oil, squirting a small amount of the same into each cylinder, rotating (by hand) 2 full engine rotations, to be repeated monthly while engine not in use - soo easy!

 

I have plugged all engine opening including carburetors.

 

Existing engine oil and fuel had already been drained, so I added 3 Litres of fresh AeroShell Plus 4 to the crankcase. Filled a clean oil can with AeroShell. Removed all 4 top spark plugs. Tilted engine forward, back, side to side, pausing for a few minutes, at each point to allow oil to percolate into all recesses. Squirted a generous amount of oil into each cylinder. Covered plug hole with rags & rotated engine X 2 times. Surplus oil is squirted out of plug hole & caught by rag. Reinsert plugs finger tight. I do this at the begging of every month.

 

I keep the engine mounted inside a dust & moisture proof purpose built box.

[lee-wave]

 

On 12/11/2020 at 1:04 AM, facthunter said:

It's commonly agreed the most rapid wear is after start up but I don't think that equates with pulling it through by hand. I'd do that say once a month and spray a storage oil in each cylinder with it's piston at bottom dead centre. The WORST thing to do is leave your plane near the clubhouse, then later in the day taxi it a few hundred meters to the hangar  and not use it for a few months.. Nev

I still believe that what happens during the shutdown phase of any motor will have a direct effect on the wear and tear on the next startup.  Added to this is the method by which the Rotax and Jab motors are shutdown compared to, say, a Lycoming.  By starving the motor of fuel in a Lycoming using 'ICO' there is less chance of detonation and less/no fuel present to wash away the oil in the cylinders walls.  Turning the fuel cock off and letting the motor stop of fuel starvation in a Jab or Rotax is almost identical to using idle cut off in a Lycoming or Continental.  

lw

[facthunter]

Certainly agree with that in principle. Combusted gases contain rubbish you don't need when it's sitting.  The Rotax is a bit of a special case. It's best shut down from a slow idle on ONE mag. briefly.  Larger Radials were often done 1200 rpm ,cut fuel and open throttles to about 1/3rd to expel spent gases as the engine winds down.. This doesn't work well  on "normal" motors as they have less flywheel and shudder too much in the mounts if you allow the cylinders to fill by opening the throttle. If the machine is used most days It probably doesn't matter much.   Running till dry in the carb is fine. Did it every time in the Tiger moth. and if you are a real smart ar$e you time it perfectly so it cuts out as you swing it into line.  The question of gaskets drying out is valid sometimes. IF it's gravity  feed, just let some fuel in and shut off again. It's always best to run a pre mix 2 stroke dry to prevent the oil building up in the carb passages when the petrol evaporates . That prevents it running rough or LEAN when you next use it. Nev