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 a
bout 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