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