rotax 912s engine failure

[wilsron]

In flight the other day, my 912s in my Kitfox 4 went rapidly from running perfectly, roughly for less than a minute, to totally quiet. Multiple attempts to restart were completely unsuccesful. Folded wings after forced landing on highway and towed home to hangar.
Rotax 912s, about 200TT
Abundant fuel in plane, so much so that it flowed out the vents with the wings folded. Drained fuel sample, no debris or water.
Removed Carb bowls, they were full, and fuel gravity flows at a rate that appears adequate to produce power without the pump working.
Removed a plug, grounded on engine and engaged starter- NO spark on either system.
Reviewed Rotax Heavy MX manual measurement values for the ignition unit, values WNL.
Generator coil Yellow to Yellow 1.5 ohm
Charging coil Red to Ground 4.6
Trigger coils .240 .240 .238 .238

Thoughts?

Thanks

Ron

[Av8r3400]

Do you have the "ACS" style off-left-right-both-start ignition switch?

There has been some debate here, but LEAF (Leading Edge Airfoils - Midwest Rotax service facility) has recommended not to use these with the Rotax's CDI style ignition due to failures.

[wilsron]

Wired with separate individual ignition switches, tested with P leads disconnected at the ignition boxes.

[Dave S]

There is a Rotax Service Bulletin on flywheel washers in some 912/914 series engines. If the washer crunches, the flywheel can loosten resulting in complete ignition failure.

Not saying this is what you experienced; however, here is the link to the SB.

http://www.rotax-owner.com/index.php?option=com_content&view=article&id=243


Sincerely,

Dave S
KF7 Trigear Flying
912ULS Warp Drive
St Paul, MN

[wilsron]

Thanks Dave
I had wondered about that one as well.
I'm not included in that sb according to my sn.
I was hoping to avoid find a problem that didn't involve pulling the engine, but it certainly looks like a possibility

Ron

[DesertFox4]

Ron, sorry to hear about your engine-out and forced landing. :eek:
Glad you skillfully got her down and you were unhurt. Nice job.
Rarely does a 912 have a total ignition failure and you've checked fuel issues so I'll be following this one.
Dave S. posted something new to me. Must have missed the washer problem associated with possible ignition failure. Check your serial numbers guys. Thanks Dave.
Good luck with the investigation and keep us posted.

[wilsron]

Thanks to each of you who have given suggestions on the problem.
Primary credit goes to Kevin at California Power Systems for suggesting a ground problem.
A Jumper across the aluminum break makes it work. I believe this was the way Kitfox suggested it be done on the original 912 back in 1993. It will go back together with different ground paths, and wire to complete the circuit in case of a similiar break in the future.

Thanks
Ron

[Dave S]

Hi Ron,

Looking at my engine, I see the current Rotax hookup has each of the two ground wires going to separate bolts on the starboard manifold. That way the chance of loosing both mags at the same time is unlikely.

I can see where the aluminum bracket combining both would cause both sides to fail at the same time if the bracket failed - probably not the best patent in the world. Your fix with separate grounds is the way to go.

Your photo helps in understanding the situation. Thanks for sharing.

Dave S

[DesertFox4]

Glad your Rotax is still healthy. Good info for everyone using Rotax engines.
I installed an extra ground when my engine went on back in 2003. We forget these things so long after our builds are completed. At least I do.:o

[kmach]

Hi,

I am very glad to see you found the smoking gun !

[Av8r3400]

Congratulations on finding the issue, Ron.

And, Thank you for sharing it with us. This is excellent information.

[Bryan]

Ron so glad you found the problem and it will not mean removing it or a tear down. More important though is the fact that you were able to get yourself and the plane down without any damage or injuries. Good Job.

[henrysamson]

My firewall forward is from about '02 or '03 and I have the same setup BUT I'm almost positive my bracket is SS. I'll be checking later.

I'm glad you have a fairly easy fix.

Hank

[Dorsal]

Nice job on handeling the situation safely and finding the cause. These type of posts don't happen very often, glad this one turned out well :)
(will also be checking the grounds on my engine)

[GWright6970]

Ron,
Excellent flying; research into what the cause of the engine failure was, and most importantly, documenting it all for the rest of us. I assure you, I will incorporate your "FIX" into my build. THANK YOU very much for taking the time to help the rest of us!

Grover

[Wheels]

FYI, I was flying around my home field today with a passenger and the 912F gave a little kick. It got my attention and I scanned the instruments but saw nothing out of the ordinary, then it did it again. I was at wide open throttle and was bringing the throttle back to 4 thousand to set up for an approach to my home and got another kick. It was transmitted through the whole plane and felt like I hit a small bird. I looked behind me at the tail section and gently brought the plane in to final.
After landing I pulled the cowling and found the grounding strap broken in half at the manifold. I remembered your post and actually was going to put in a grounding strap this week. As it stands, the plane is "grounded" until I get a new strap and a new bracket. I'll do like you did. Thanks for the post. Here's a pic

[Paul Z]

I had the same thing, but I caught the broken bracket in the pre-flight. I am not sure when it broke, I never had any indication in the prior flight there was a problem. I ordered a new bracket, & installed it. I need to check the grounding.

[herman pahls]

I compared my grounding situation on my 912s with the photo on reply #7 of this thread.
I only have 1 grounding wire that looks the same as the 2 wires in the photo.
This wire is bolted directly to the head where the coil supporting bracket is bolted as shown in the photo.
My questions are:
1. Should I have 2 grounding wires or do different year engines have variances?

2. Seems like the grounding wires should be bolted directly to the head instead to the bracket which can break as shown?

3. Should there be 4 brackets that are similar to the one broken in photo that support the CDI box's/coil packs?
My engine only has 3 brackets and 1 of the rubber isolators does not have a bracket attached. This does not appear to be factory.

Years ago I also had a successful dead stick landing and want to avoid a 2nd.

Thanks
Herman

[Slyfox]

with all this, I went out to my plane a couple weeks ago and looked at mine. now my engine is of I believe 09 dated. so it's within 5 years. I knowing ahead of time of this issue, went and used a nice sized braided wire about an 1/2 inch wide about 8 inch long and connected to the head, from there my ground wire, main one, from the battery connects to that with the same bolt. the bracket ain't going to break, because it's not on mine, so that ain't happening. I adle clamped in a couple areas the whole set up (modules) to the engine mount. it ain't going anywhere. the braided wire is direct to the ground wires for the modules.

[Dave S]

Herman,

The single grounding wire doesn't sound right.....if you didn't build the plane, it could be non-standard.....Also a chance the other grounding wire may be hooked up in a hidden place - it is amazing how many places ther are like that on an engine. Can't say I am familiar with every rotax engine ever built, however, with two modules I am thinking there should be a ground wire for each.

Maybe a photo?

Sincerely,

Dave S

KF7 trigear
912ULS
Warp drive
St Paul, MN