Mentioned here
In conjunction with a borescope, this would on the TB20 enable the 50hr to be done without lower cowling removal, which would save most of the maintenance induced damage.
It would be great for those who due to airport politics have to work outside.
I don’t, and I would not use vacuum oil extraction.
IMHO serious aircraft maintenance means, every 50hrs:
These are the minimum requirements, more according one’s AMM or other relevant publication.
I won’t not remove the cowling after 50 hours of flight. Everytime I remove the cowling I find something that’s a non-issue but that might have evolved into something serious if not fixed
What do you mean by maintenance induced damage here?
I have not yet tried vacuum extraction on my Lycoming, but I’m not seeing how it would prevent one from performing the other items on Dan’s list.
On some aircraft – thankfully not mine – it’s not easy to open the drain plug without making a mess. Extracting the oil first could help, since when you remove the plug, there is not a flood of oil going everywhere.
One item some people, even A&Ps, miss on Lycoming engines is to check and clean the oil suction screen. That’s actually killed people.
Dan wrote:
I would not use vacuum oil extraction.
Forgot to add – I have read that in some very cold climates people extract the oil before parking for the night and keep it in a warm place, and return the oil to the engine in the morning before flight. No idea if this is a good or bad idea, but probably better than nothing if you have a cold start ahead of you. I’d of course worry about piston/cylinder clearance in a case like this.
eurogaguest1980 wrote:
it’s not easy to open the drain plug without making a mess
Yes that helps. Draining the oil sump with that drain plug is like nothing. It’s slow, but with a tube it just fills into a can and it’s absolutely clean. And there’s plenty of items to check in the meantime…
I won’t not remove the cowling after 50 hours of flight.
I really like cowlings that have large doors on both sides to allow a fairly complete engine compartment inspection before every flight. Both mine have had that, I take a look every time the engine is shut down and decowl once a year to allow bottom spark plug removal. I have a rather odd paranoia about the throttle cable, and check its attachment and security every time I fly.
I have a quick drain valve which in conjunction with a long hose makes draining the oil easy. I use an old piece of SCAT tubing pushed up and around the drain valve instead of trying to push a piece of smaller diameter tubing onto the valve. The engine has no oil screen but has a remote filter that can be changed without cowling removal, if you like.
Drain the oil thru fine mesh
That’s very true; one cannot do that AFAICT without lower cowling removal unless one has very long arms 
Everytime I remove the cowling I find something that’s a non-issue but that might have evolved into something serious if not fixed
The Q is whether you would not see that with a decent borescope too.
What do you mean by maintenance induced damage here?
Just damage to fibreglass cowlings. These are highly vulnerable to wind so one cannot do a service outdoors when it is windy. They can be laid down on grass but one still has to be really careful.
it’s not easy to open the drain plug without making a mess
That works fine with a modern type of drain plug (not the Lyco original). The problem on the TB20 is that one would need a very long arm to push the pipe onto the drain and unlock the drain, without lower cowling removal.
Obviously my proposition here assumes you have a decent borescope, not the usual junk. Unfortunately even $1000+ borescopes are junk – unchanged for decades. It also assumes that one can push a suction pipe, ia the oil filler hole, all the way down to the bottom of the sump; I am not sure one can. But that will be engine dependent.
One issue I can see is that oil analysis may yield different results if vacuum was used, because you would suck all the oil out and then take a sample from the container, whereas in normal oil analysis you do an engine run up to base of working temp range (90F on mine) and then drain it, and take an oil sample a fixed time after the start of the drain – 1 minute in my case – for consistency.
If I were thinking of vacuum oil extraction, it would be on the basis of a 25hr oil change, where a 25 hr oil change would otherwise not occur.
At 25hrs on the basis of normally running to 50 hrs, you can quickly and cleanly change the oil but wouldn’t necessarily change the filter or send analysis.
I would do it after a flight.
We use oil vacuum on the boats all the time, as it isn’t really an option to drain from the sump on any boats I work on.
GA_Pete wrote:
If I were thinking of vacuum oil extraction, it would be on the basis of a 25hr oil change, where a 25 hr oil change would otherwise not occur.
At 25hrs on the basis of normally running to 50 hrs, you can quickly and cleanly change the oil but wouldn’t necessarily change the filter or send analysis.
I would do it after a flight.
We use oil vacuum on the boats all the time, as it isn’t really an option to drain from the sump on any boats I work on.
Indeed – that’s a good idea. I stick a borescope in the oil drain and look around, no sludge in my lyco – I should do the same in the cars to see what’s down there.
I’m guessing if you run mostly unleaded, good quality oil, and change the oil frequently there should not be too much sludge in an aircraft engine.
