Roger Lee 912uls

Hi RW,

Opinions are what makes the world go around and it's good people have them. This way we all learn.

You suggest lots of variables in your post, but Rotax is hard and fast on their time line with no variables. I know why they do it, but as you demonstrated there are many variables to consider for each plane and owner. For all the reasons you posted that's why I'm  not a hard and fast proponent of a solid hard rule about TBO.

p.s.

How's the BP today.  :) 

Hugs 

Hi again Roger

OK so let us look at this another way.  If an engine fails before TBO, we know there has been many over the 3 plus decades of Rotax 9 series, should we not lower the TBO?  To use the logic you propose this would be reasonable as well. 

The engine started with an 800 hour TBO in 1989.  Only engines that had traceable hours, with logbooks and qualified maintenance, were allowed to be used as fleet hours.  This is reasonable in that experimental mostly vary by OEM and even the kit builder or owner.  As experience accumulated TBO was increased based on best available and verifiable information was accumulated.   

I drive a 25 year old truck.  That however does not imply that everyone can get that time out of one or even suggest it is a good idea to do so.  For the most part you cant even buy parts for my truck now as the auto wreckers even stopped hanging on to 1999 model year trucks.  So yes a lot of old Rotax engines hang in there but I do not believe it is more than good luck in many cases.  I still believe in preventative maintenance and change things before they fail. 

They have moved times up in the newer engines with stronger crankshafts and crankcases on the type 915 and 916.  Few people have noticed the allowance of "flight time" to be used for TBO and inspection calculations.  (see attached 916 wording)  So basically those engines can gain perhaps 300 or 400 hours of total time by that method.  (wheels up time) Still Rotax expressly says that does not apply to the others. 

I will leave it at that. 

Cheers