Minimum oil level for aerobatics - 8KCAB?

[Halhayden]

I’ve just started aerobatic training in my Decathlon and am wondering about the minimum oil level. My AFM has contradictory statements - one says 7 quarts minimum and the other says 6. Since having the oil changed after break-in, I‘ve been at 6 quarts.

However, after spin recovery the other day, we noticed a slight shudder/vibration after adding power to climb back up. My instructor and I both felt it and believe it came from the prop. When we repeated the situation, it occurred again, so we terminated the flight to try and figure out what was happening. In discussing it with several people, one suggestion was that the prop governor might have been struggling due to lack of proper oil pressure after the spins. I took the plane out again yesterday solo and just tried some shallow dives and climbs at various power and prop settings but did not experience the vibration.

Would appreciate any thoughts on this!

 

[Bob Turner]

My book says six. My very gentle aero needs five and a half. What you want is oil pressure.

If I am low on oil, or that pesky O-ring gives out, the pressure can take an instant to come back up when inverted. If it is more than an instant - say, two seconds - the prop goes to maximum pitch and rpm slows.

The giveaway for the O-ring seems to be if you roll right side up and it takes more than a second to get pressure, you need a new O-ring. There is plenty of room for double O-rings on the plug, and I have considered it - but my last genuine Lycoming O-ring has lasted ten years.

 

[Bartman]

which o ring?

 

[Big Ed]

I've always done 6 qts in my Super D, per my AFM. Never had a problem. Any quantity spec like that is going to have a substantial buffer, so I would expect you would have to be down to 5 or 4 to actually have a problem.

 

[Bob Turner]

There is an aluminum plug in the oil pan, held in place with the oil screen. Keeps the oil pump from sucking oil directly from the sump.

Below 5 1/2, expect delays in pressure during transition from inverted.