Originally Posted by waterboy2110
When I went to pick up the engine Bryan and Ronnie were getting ready to teach a class. Ronnie made the statement that since the quality of the fuel was no longer in question then the shroud or the installation of the shroud was the new point of focus. He mentioned the O rings being pinched. They are not and fully in tack. He mentioned the manifold coming loose - it was torqued to spec and torque sealed with no signs of movement. From what I can tell the "official" expert analysis from Rotax is what ever Ronnie says it is. I've seen no evidence of the engine being opened. I was never shown pictures of the cases split. We took plenty of pictures of the cylinders coming off. I have no reason to doubt Bryan did what he said he did but I have only his word.
Van's is switching to using the Rotax 912iS
on the RV-12, (not the 914).
There are no airframe electrical dependency issues with the 912iS like there is with the UL engine. Once it has been started, the iS engine generates its own electrical power... fully independent of the aircraft's electrical system. There are back-up modes of operation designed in so that power could be supplied by the airframe electrical system if the Two
(fully redundant) methods on the engine both failed at the same time (unlikely).
The decision to delete the cooling shroud from the kit was the result of flight testing done during the development of the iS FWF installation. The iS has cyl temp measurement on all 4 cyl (unlike the ULS which only checks Cyl 2 & 3..... which notedly one of those happens to be the cyl that failed in this case) which allowed a more detailed understanding of what temperatures the entire engine was running at.
The shroud was deleted for the purpose of simplifying the build and to reduce the kit cost. Deleting the shroud removed the need for disassembly of the top of the engine, and thus the potential for a builder to make a mistake.
It was not done under pressure from anyone associated with Rotax. In fact there has never been any mention of a concern with the design of the shroud to Van's by anyone at Rotax.
The blog photos show the removed cooling shroud and speculation that cyl # 2 wasn't getting enough cooling air because of the visible evidence on the shroud showing that cyl #2 had gotten much hotter than the other 3. There is no evidence at this point to indicate that the shroud precipitated the failure (see comments that follow). It is entirely possible that some anomaly caused the pre-ignition / detonation type event and that the very high cyl head temps that would result from that, caused the darkening of the cooling shroud in that area.
- There is now 575+ RV-12's flying.
- The majority of those have the cooling shroud installed.
- There is a lot
of RV-12's that regularly fly in very hot temps. There is nothing special about the conditions in southern CA that are more severe than Southern AZ, NM, TX, FL, GA, LA, AL, etc., along with the hot temps that can happen during the summer in the northern states (and other parts of the world for that matter).
- With 575+ RV-12's and almost 10 years now since the first customer built example flew, there is only one other instance of similar engine damage and the cause of it is well understood. In a nut shell, the plans were not followed and the builder made a mistake, and two cyl on one side of the engine were damaged as the result of an excessively lean condition. You can see photos and read about it in the side bar on page 13 of this old RVator Issue
. In this particular case the engine was repaired (by CPS), though not under warranty, and as far as I am aware is still happily flying today.
Rotax has clearly specified the procedures for filing a warranty claim. The documentation is supplied with every new engine and is also available in digital form on line to all engine owners. In this case the second engine was I presume purchased directly from a dealer, and not Van's (CPS?). If something failed on that engine, the dealer would not personally warranty it. They would process it the exact same way that this incident needed to be.
So as this discussion continues my hope is that everyone involved will keep in mind all of the facts that we actually know for certain...........
That 575+ RV-12's (most with the cooling shroud installed) have been flying for many thousands of hours, spread over an almost 10 year period of time. Many of those hours were in extreme temperatures (some even hotter than when this incident occurred), while using 91UL fuel.
And with other than this one instance, zero reports of engine damage.
I feel bad that this has happened. The whole purpose of Van's being in this business is to provide kits for airplane that people can build themselves, that have an unprecedented cost vs performance ratio. This occurrence bothers us just like it would anyone else in the RV community.
Having said that, I still think there are details regarding this that haven't been discovered yet.
I have only a limited knowledge in analyzing engine damage such as this so I will leave those comments to those that do, but there are some things in the photos that I think raise some (so far) unanswered questions.
At least one of them would be to see the Cyl head temps and other engine temp readings for the flight posted on the blog. As mentioned earlier, the failed cyl is one of the two that has a cyl temp sensor installed.
<EDIT> After a closer look I see that the CHT data is available and that it shows there was only a 5 deg difference between the left and right side of the engine (CYL 2 & 3).
It looks like damage was beginning to occur on cyl #4 (small holes in the combustion chamber portion of the cyl head). This would jive with something abnormal going on on the left half of the engine. Could be anywhere from an induction leak on that side like the other engine failure i linked too, or improper carb synch, or a carb problem, etc. (but all purely speculation).
There is also an asymmetrical appearance to the carbon pattern on the #4 piston and the combustion chamber portion of the cyl head.