Joe, Sorry to hear about your problem but
glad to hear you brought her back safely. Does certainly appear you have
a bad apex seal. You might want to check your ignition timing. I
once mistakenly (of course - who would to it intentionally {:>)) sat my
static timing to 45 deg rather than 35. I noticed while flying that If I
opened up the throttle wide open the note of the exhaust changed to a staccato
popping. Well did not fortunately lose an apex seal but I found the
center electrode ceramic cone was missing for two of the 4 plugs and cracked on
the other two. Just lucky they didn't take out the apex seal. So you
might check that timing just to be certain.
The weather today in the Seattle area was
marginal for flying - but a nice hole opened around my home airport (KAWO) and
I was there tinkering with the plane anyway (re-torqueing the prop)- so up I
went. I did 4 touch and goes just for a wee bit of practice and then departed
the pattern toward a bigger hole that would be legal to climb through VFR. I
flew about 30 miles northwest of the airport out to the edge of the
Puget Sound and enjoyed just being in the air. Power
setting was about 4400RPM and I was loping along at a lazy 135kts. I
turned around and headed back for Arlington
and decided to ramp up the power to ramming speed - errr I mean cruising speed.
In a few minutes I was cruising along at 170kts at about 5500RPM. Then all of a
sudden BAM - the engine stumbled and RPM's dropped to 2300RPM. I
immediately throttled back and switched tanks while turning toward the airport.
Altitude was 3200FT (about 3000AGL) and I was maybe 7 miles from the airport.
The engine was running real rough and wouldn't give me more than 2300RPM. Even
with that little bit of power I ended up entering the 45 to the pattern at
about 800 above pattern altitude. It was pretty slow at the airport so I easily
made a normal landing and was able to taxi back to the hanger under power.
At the hangar I double checked everything
I could from the cockpit - fuel pressure good at 36PSI, oil pressure good at
55PSI at 2300 RPM, MicroTech ECM showed "OK" for the size major areas
it monitors. So, I shut it down and pulled the cowl. I pulled the prop through
a number of times and it seemed that there was a couple places where I should
have been hearing a "pop" in the exhaust but didn't. I also notice
that there is a nice ding in the prop that is about an inch long - that wasn't
there when I left (remember I'm a pusher).
I got the engine compression gage and
proceeded to take the spark plug out of the front rotor - top - BR9EQ-14. Hmmm
- I don't remember there being a casing around the electrode - and why is that
casing sliding? Apparently the casing around the electrode broke
somewhere inside the sparkplug and into two halves long ways down the
electrode. Each half slides freely up and down the electrode and even sticks
out a little from the end.
I put the compression gage on and it
looks like I get 30-30-70 when I turn the engine over. I tried this several
times and there is definitely a couple of places where it only goes to 30. So I
double check the location of that ding in the prop - hmmm it's exactly even
with the bottom of the exhaust - right about where an apex seal would come out.
I put two new BR9EQ-14's in both rotors
and did a quick run - 2300RPM rough is the best I could get.
Some time this week I'll go up and yank
the exhaust so I can see the apex seals - my guess is I'm missing at least one.
Bummer.
Joe Hull (getting tired of little
surprises in the air).
Redmond/Seattle WA, Cozy-Mazda Rotary
71hrs