From here
I was taking my friend flying once and because it’s a Rotax powered engine, I had to turn the prop to glugg the engine and check the oil. My friend asked me what I was doing as it was his first time in a small plane and had never seen such actions performed. I told him I was winding up the elastic band which provided the power to turn the propeller. He believed me. 
However he got rather upset and felt insulted when I used my usual chant when checking aileron deflection – to you, up yours…….
I had to turn the prop to glugg the engine and check the oil.
This just blew me away when I first flew a Rotax plane. Imagine if you bought an expensive, fancy car, and you had to push it up and down the driveway half a dozen times before you tried to start the engine.
johnh wrote:
I had to turn the prop to glugg the engine and check the oil.This just blew me away when I first flew a Rotax plane. Imagine if you bought an expensive, fancy car, and you had to push it up and down the driveway half a dozen times before you tried to start the engine.
Does it not have some oil indicator?
Does it not have some oil indicator?
Absolutely. And the way you make it work is by turning the prop through about 20 blades. Honest.
arj1 wrote:
Does it not have some oil indicator?
Rotax engines operate via a dry sump oil system and if the engine’s not started in any extended period of time, the oil seeps due to gravity from the tank into the engine which means you can’t accurately check your engine oil level. Sports cars use a dry sump but typically they will have two oil pumps, one to pump the oil around the engine, the second pumps the warm oil back to the tank via the cooler.
Rotax doesn’t use the second oil pump, instead it uses gases which blow past the piston rings to pressurise the crankcase which forces the oil back to the tank. However to check the oil level, you need to manually move the oil from the engine to the tank; when it’s complete, the engine “burps”. To do this, you turn the engine over via the propeller, using the blow back pressure of the cylinders to force the oil back into the tank. Depending on how cold it is, when the last engine operation is, how worn your engine is and what difference in height the oil tank has in relation to the engine, you might need to turn it a matter of 20 blades, you might be propping it for around 5 or 10 minutes until the engine burps.
At that point you can reliably check the oil level……
Often people don’t know that or don’t want to know that and. Oil dripping out of the cowling is then the consequence because without that procedure (you can instead run the engine for 10 seconds) the oil dipstick shows less oil than is actually in the engine and people overfill the engine.
Clipperstorch wrote:
Oil dripping out of the cowling is then the consequence because without that procedure (you can instead run the engine for 10 seconds) the oil dipstick shows less oil than is actually in the engine and people overfill the engine.
Doesn’t the same happen when one fills up a Ly/Contizaurus to the official “full” level? Mine will spit out a quart or two out some vent almost immediately and then happily keep on burning what is left.
Speaking of which, what are the minimum levels for engine oil in a certified engine? I don’t think my POH mentions that, just the max.
The engine TCDS has this data, for a Lyco.
Steve6443 wrote:
Depending on how cold it is, when the last engine operation is, how worn your engine is and what difference in height the oil tank has in relation to the engine, you might need to turn it a matter of 20 blades, you might be propping it for around 5 or 10 minutes until the engine burps.
Yes, the new Rotax that we have indeed usually burps after no more than one rotation of the propeller.
Not sure if this discussion belongs in the ‘jokes’ section [ moved since ]
The burping procedure is also useful for: a) checking for any awkward engine noises, b) feeling compression of all cylinders, c) checking the alternator belt and d) pumping some oil through the engine.
You can actually check the engine oil without burping. If the level is slightly below the minimum you can be assured that, should you have burped, the level would have been fine.
