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Scoring around the spark plug holes, especially when combined with matching wear on the apex seals, may be a byproduct of the sustained intense combustion environment. The area right around the spark plug is the hottest part of the engine and expands more, this causes the housing to actually expand slightly into the path of the apex seal. The overall effect is an increase in wear to both the housing and the seal. I suspect your discoloration to the side of the wear is from the same cause. Unfortunately, overall engine coolant temperature is not the factor here, but rather the temperature of the housing at that specific point, which you can't do very much about. Better lubrication of the combustion chamber via more premix and retaining the oil injection ports on the rotor housing will help combat this wear, but for the most part you cannot prevent it entirely.
I would not be surprised if many high-time rotary engines in aircraft turn out to have similar damage/wear. As you found, of course, compression is not seriously affected, but the wear will occur at an increasingly fast pace once it starts. When Mazda was still making new rotor housings, it was not a serious issue as the wear would usually not be the thing that caused a failure, but now that rotor housings are getting harder to find the wear is a problem as you often should replace a rotor housing that has this problem during a rebuild.
Unfortunately I can't offer much insight into the power loss. Hopefully you will be able to find the cause.
On Fri, Sep 2, 2011 at 9:51 PM, Bill Eslick <wgeslick@gmail.com> wrote:
I have been holding up reporting this until all the facts are in, but that might never happen, so here we go.
Good news: No injuries.
Bad news: I have some work to do.
Photos at: http://www.tiny9.com/u/2101
On August 16th at 10 AM, I lined up for takeoff at my home airport (3600' paved) into a 5 knot headwind. I had just finished changing the oil and filter and plugs. Run-up was fine, so off I went. Approximately mid-field, and a couple of hundred feet in the air, it suddenly and without any warning became very silent.
Hit the big switch which puts direct battery power to everything engine, but no noise. No more time. At this point flying the machine becomes THE priority. Dropped the nose and was amazed to see a little bit of runway under the nose! I had fully expected to land in trees, houses or the river, so I dove what seemed like straight down to capture as much runway as possible while (somehow) holding the electric flap switch long enough to get full flaps (noticed this later). Pulled probably my best round-out ever - no bounce. Brakes to max and tail up for weight. I think my sub-concious put it all the way on the nose to try to prevent going through the fence and down the hill. Wheel skid starts about 200 feet from the stopping point. Skid marks from the wheel pants, cowling and prop run about the last 50 feet. It stopped nose down just off the end. The tail was still over pavement. Pushed the slider canopy UPHILL, stepped out and down. Noticed that I was not even scared by the whole event. Interesting. Never even considered trying to turn around. Pre-thinking that non-option apparently paid off.
More good news. No FAA or NTSB as it was a non-reportable incident. Didn't even bend the gear legs. Also, my neighbor crashed in a Challenger about 10 minutes earlier at the city airport about 10 miles away. The police and rescue types were headed that way (they had injuries) and were not interested in my minor mishap.
As for the engine. When we got it back to the hangar, the prop would turn only haltingly. You could feel grinding going on inside. First try at turning had it come up hard and stop. More fooling with it and it gradually came looser and would turn. Really looked like something came loose in there. Pulled a plug from each rotor and did a compression test. Rotor 1 was 80-80-80. Rotor 2 was 2-2-2. More proof that something had come loose. With that evidence, the insurance company allowed me to remove the engine for inspection. What I found was a pile of ground up ceramic junk. All the seals were still fine. Lots of time went in to finding where that stuff came from. Went through every inch of the induction system. Finally Jason Hutchison (my other on-airport rotary guy) broke the code. While the RV was standing on it's nose, this crap from my burned-out Hushpower II ran back up the manifold and in the exhaust port. That is what was grinding. Crap. Now the entire thing is off the firewall including the engine mount. All the wiring is disconnected (did not find anything loose or missing). I spent the morning looking under the panel for any loose or broken wiring, but found none. When I get the EC-2 out, Jason wants to plug it into his plane and we'll do the plugs and injectors test. If that checks out, Tracy, it is coming to you for a good look. I don't know what else to check. The engine quit just like somebody reached over and turned off the ignition. No stumble, no hiccup, just instant silence. I honestly do not know if the prop was turning or not. I suspect not, due to the silence and the fact that one blade is untouched.
As you can see from the photos, there was something going on with Rotor 1. Wear is apparent down stream from the plug holes and all 3 apex seals are starting to chip in the center. There is quite a lot of carbon also on the rotors after 170 hours.
Going forward, I have decided to look at resale value for if/when my RV-12 days arrive. This means putting a (gasp) IO-360 on it. The rotary has given me a safe 10-year run (til now, of course), so I have no regrets, but this is an opportunity to make some changes, and parts are already on the way. I will still be hanging out at the engine tent at S-n-F and wherever else gatherings happen. Hope to be flying by the first of next year....
I'm sure some of you will have suggestions about what might have gone wrong, and I welcome any kind of speculation, but bear in mind I am just looking at a pile of parts and wires at this point. Both fuel pumps were on, tanks were over half full, crank angle sensor worked fine.
Guess it's obvious that I now have a RD-1A, EC-2, EFI Monitor (Ed's), Felix 68/72 and Props Inc 68/72 wood props and LOTS of engine parts (my whole 14-year stash) available! And priced to sell!
Bill Eslick
RV-6 13B/NA EC-2 RD-1A 750 Hours
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