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