Burping advice not on target

Hi Roger,

I read the article by Mike Busch that started this (see link below).  The article addresses key operated mag switches, and the issues surrounding them.  At one point in the article Mike suggests that if you must rotate your prop to a certain position, say for the tow bar clearance, then it's safer to rotate it in reverse. He even discusses the affect this has on vacuum pumps. At that point in the article there is no exception stated for Rotax 912 engines, leaving Rotax owners to wonder if they are in danger as Steve did. 

It's unfortunate that when following up on Steve's question, Mike suggests turning the engine in reverse of normal direction.  As you say, he is obviously more versed in conventional engines than Rotax engines. Mike has some fantastic articles and books and is a major contributor to the aviation community.  I've not met him personally, but I have read and enjoyed much of what he has written. Rotax engines are different, and I don't think the GA maintenance community fully embraces these differences (yet).  I suspect Mr. Busch is the type of guy who will take this correction constructively, learn from it, and amend his future recommendations.

2311_R&W.indd (savvyaviation.com)

Hello all...

Just to be clear, Mike Busch knows zip about Rotax.  If you use his info then you will be supporting your local repair service soon.  Just fair warning.  Mike B is a great resource but not for Rotax.  

Cheers

Hm, checking for tow bar clearance is less than 1/2 turn, I‘d assume. Hard to picture that less than half a turn backwards will destroy the Rotax 912.

Of course with burping that’s a totally different story. It depends but 5 to 10 complete, some report more, turns to get the burping sound may be common or at least not unusual. I‘d neither dare or suggest to perform the burping procedure backwards - not a good idea with, most likely, bad effects on the engine. Has Mike Busch really suggested that (multiple complete turns backwards)?

Actually I wonder if you’d ever get a burping sound when doing it backwards, perhaps… I won’t be tying? Any practical experience out there?

As Others say,

  Mike Busch is a strong advocate for some changes to how people maintain Lyconentals I have been to a few of his talks. However again he appears to know nothing about, or for some reason never mentions, Rotax engines.

I have come across a few people whom love his advice and seem unable to even contemplate that Rotaxes are different and when they shift to a Rotax engine endlessly complain that it is not "right".

However as my LAME (A/P) says the difference is that a Rotax actually gets to TBO...

So the question of can you burp the Rotax turning backwards...NO, not ever.  The oil pump is a suction pump to draw oil into the pump and force it into the oil filter and beyond.  In turning backwards you will create an air pocket and possibly unload the hydraulic lifters....the start of the death of your expensive engine.  There is no reason a person can't turn the prop in the correct direction to clear a tow bar, that seems all to obvious.  My goodness how hard is it to attach or remove a tow bar?  Every tow bar I have seen is so simple that just seems lazy to me to want to avoid 30 seconds of work.  

All engines will have sensitive areas, all.  For Rotax it is how you treat the oil system given it is a dry sump.  It is not a direct drive wet sump like a Lyccoming or Conti so we have our little quirks to make it last the longest like burping and turning the prop in one direction only.  I am at a complete loss as to why we would want to transfer any suggestions from direct drive wet sump engines to Rotax.  Perhaps some people have never seen a large hole in the crankcase where the rod came out, that's the problem we want to avoid. 

Cheers