Rotax Piston Meltdown

[Art_N412SB]

Originally Posted by tomkk

The note that just precedes this chart is "NOTE: Only applicable on pressure altitude below 3500 ft." (sl-912-016-r1). Not what the situation is above that ...

That makes sense. In a normally aspirated engine you loose 1in per 1000 ft of altitude gain. Taking off above 3500 ft you probably could not generate enough Manifold pressure to get into the shaded area of the chart.

My home airfield is at sea level. I would probably fly a different take off profile if I were operating above 3500 ft.

Best regards,
Art

[Jamesey]

Loads of discussion here on this failure. However, does anyone know how many other similar failures on the flying RV12?s have occurred (if any).

[JBPILOT]

Did you take a sample of the fuel to an independent analyzer to verify it was at least 91 ?

[Piper J3]

Originally Posted by Jamesey

Loads of discussion here on this failure. However, does anyone know how many other similar failures on the flying RV12?s have occurred (if any).

Or to add to this question... Scott mentioned that the 12 demonstrator has more than 2000TT. I'm wondering if its still on it's first engine? Has any top-end work been done to it? Compressions still good?

Perhaps someone else with high-time RV-12 can chime in...

[rvbuilder2002]

Originally Posted by Jamesey

Loads of discussion here on this failure. However, does anyone know how many other similar failures on the flying RV12?s have occurred (if any).

The only other engine failure in an RV-12 was builder induced.
I mentioned it earlier in this thread. You can read about it on page 13
in this old RVator

Originally Posted by Piper J3

Or to add to this question... Scott mentioned that the 12 demonstrator has more than 2000TT. I'm wondering if its still on it's first engine? Has any top-end work been done to it? Compressions still good?

The engine was replaced (but don't remember the exact total time... maybe 1700 hrs). The core engine was fine and had never had anything done to it other than the Rotax prescribed inspections and maint. I am confident it would still be running great right now if not removed but the sprag clutch was acting up. Doing demo flights and other flight test operations the prototype probably has at least double the engine starts per flight hour (and probably way more than that) that a typical RV-12 does. Replacing the sprag clutch requires opening up the engine. Down time during peak season has to be kept to a minimum so swapping in a spar that we had made the most sense.

[Mel]

Not an RV but just a reference point. I built a Zenair CH601HDS in 1995 with a Rotax 912UL (80hp). That engine now has almost 2000 hrs with nothing but routine maintenance and still runs like new.

[waterboy2110]

While discussing this with some mechanic buddies they mentioned a 12 here in CA for sale because the engine gave out. Don't have the specifics.

I don't think it's reasonable to imply there is only "one" other failure in the fleet given my experience. Vans never asked me anything about the engine - they simply told me to call Lockwood. I doubt there's any record of my failure with the mothership prior to this thread and I started this thread six months after the failure.

If there's a desire to make statements as to the number of engine failures perhaps a protocol could be established when builders call in. I've spoke to five people at Vans, seven if you include Scott and Vic.

If we really want to know the details gather up the builder info and send out a short survey. That would be useful data in my book.

The fuel was tested by the company Phillips 66 uses for all the SF Bay Area fuel they supply. The report is on the blog.

[rvbuilder2002]

Originally Posted by waterboy2110

While discussing this with some mechanic buddies they mentioned a 12 here in CA for sale because the engine gave out. Don't have the specifics.

I don't think it's reasonable to imply there is only "one" other failure in the fleet given my experience. Vans never asked me anything about the engine - they simply told me to call Lockwood. I doubt there's any record of my failure with the mothership prior to this thread and I started this thread six months after the failure.

If there's a desire to make statements as to the number of engine failures perhaps a protocol could be established when builders call in. I've spoke to five people at Vans, seven if you include Scott and Vic.

I am not at all clear how if no one at Van's asked you about your engine and that you have spoken (or communicated via text message) with seven people there, that it implies there could be other failures that are not known about.
You mentioned you were calling because of an engine failure, correct?

I also don't understand what is unreasonable about saying there has only been one other failure if that is all of the information that is publicly available.

Nothing in the world is a certainty.
I admit it is possible the other one I mentioned isn't the only one, assuming someone had a failure and told no one at Van's, told no one else that took the time to mention it on line (until now like you have, which would be extremely rare) and didn't make any attempt to file a warranty claim with one of the Rotax Dealers.
I think most people would agree that was rather unlikely, but yes, not impossible.

If the one you mention is real, can you provide some details? A link to a for sale ad of an airplane with a broken engine perhaps?


Your post seems to have a desire of inducing doubt that there are only two (for what reason I am not entirely sure).
Maybe there is one there in CA for sale with a failed engine, but without knowing what the cause was it is not relevant to implying a problem with RV-12's......... an engine failure could be caused by something as simple as an improperly tightened oil hose coming loose in flight causing a loss of oil and failure of the engine. Surely you can agree that though unfortunate, that would be entirely the fault of the builder/maintainer

I think it would be of more value if there was emphasis on discovering what the cause of your engine failure was.
I think there has been requests for more info/photos that might provide some answers, but I haven't seen that info presented yet.

[AndrewR]

Originally Posted by rv6ejguy

From my experience, this is totally incorrect. You can see that detonation from the 2 latest photos I posted, simply snapped the ring lands with no other skirt or heat damage anywhere.

Originally Posted by rv6ejguy

The first set of 4 photos I posted, photo 1, the engine detonated moderately to heavily for about 1 second, 5 or 6 times over a couple days. I got out of the throttle/ boost immediately each time. Then this happened the 7th or so time.

That is very different to detonation sustained for a minute or 2 at maximum power. There is detonation that breaks things within seconds. There is detonation that can continue for a long time without damage. Presumably, somewhere in the middle is detonation that does damage over 1-2 minutes. What does that damage look like?

Originally Posted by rv6ejguy

Detonation results in pressure spikes many times what you would get during normal combustion but it is of extremely short duration so it does not transfer much heat to anything which is why you see pressure damage but no heat damage.

Everything I have seen on detonation says it can shock the boundary layer that protects the piston and head from the heat of combustion, with the result that they overheat. That is not consistent with "no heat damage".

Another thing that destroys the protective boundary layer is hot gas escaping through a small gap. So if you damage the ring seal and the blow by is severe enough i.e. you maintain high power, the combustion gases act like a blow torch on that area of metal.

Originally Posted by rv6ejguy

Detonation also always occurs ATDC where cylinder volume is increasing and crank angle is more optimal where pre-ignition is of long duration (normal combustion started before spark initiation) and always occurs BTDC so pre-ignition adds a ton of heat while effective cylinder volume is decreasing, adding even more heat.

Detonation is short enough that cylinder volume change and crank angle are irrelevant.

Your point about pre-ignition is important though, it occurs before normal ignition so you have a cylinder full of unburnt mixture. The heat and pressure are applied to the whole combustion chamber so you would expect to see generalized heat damage - not just one area. With pre-ignition I would expect to see some evidence of melting on e.g. other areas of the piston. I do not understand how pre-ignition damage would be so localized.

Detonation on the other hand is likely to happen in the areas furthest from the plug and last to burn. The damage could quite reasonably be localized to those areas, and that is what I see here.

[bret]

Your last part is where I agree with you, in post 88 I was thinking the same thing, one plug not firing, end gasses detonating opposite the firing plug. detonation can happen after one plug firing. Think of speed of flame front verses detonation, turtle is the flame front starting the burn at one end and then the rabbit blows the rest up at the other end.