I planned on flying the Chief early this morning, so I arrived at the airport before 7, did a through preflight, pulled it out, started (eventually -- it took several tries), and taxied out.
Everything sounded fine and runup revealed no issues. I lined up on 10 and held brakes, added full power -- everything good. Release and roll. I was airborne before the first taxiway and climbing strong eastbound. I turned south at about 500' AGL and climbed to 1400 when I sensed a change in tone. There was also an unusual odor -- faint, but different.
I didn't wait for power loss -- I did a 180 and headed back to the airport. There are plenty of open farm fields underneath but a return to the airport would be best.
I maintained full power and started to notice the RPM dropping a bit -- not much, maybe 200-400 RPM. Yet something was definitely wrong. I maintained altitude until two miles out then reduced power, slipped aggressively, lined up alongside 26 on the grass, slipped some more, reduced power to idle, and touched down gently.
At reduced power I could hear a clear miss in one cylinder very similar to the sound when I lost a plug. I taxied back to the hangar, shut off the fuel and switched off mags.
Once I pulled it back in and removed the cowling the problem was all too easy to spot -- the gasket that seals the cylinder head to the base had failed:
Two of the nuts that hold down the head (studs come out of the head) were loose. I checked them all about 5 flying hours ago, so I'm not sure if they worked loose in that short a time or...? The hole caused the cylinder to lose all compression. In a barely 65 HP engine the loss of one cylinder is significant. The hot exhaust was also burning up the carb heat SCAT tubing.
Parts ordered and repairs to come...
Everything sounded fine and runup revealed no issues. I lined up on 10 and held brakes, added full power -- everything good. Release and roll. I was airborne before the first taxiway and climbing strong eastbound. I turned south at about 500' AGL and climbed to 1400 when I sensed a change in tone. There was also an unusual odor -- faint, but different.
I didn't wait for power loss -- I did a 180 and headed back to the airport. There are plenty of open farm fields underneath but a return to the airport would be best.
I maintained full power and started to notice the RPM dropping a bit -- not much, maybe 200-400 RPM. Yet something was definitely wrong. I maintained altitude until two miles out then reduced power, slipped aggressively, lined up alongside 26 on the grass, slipped some more, reduced power to idle, and touched down gently.
At reduced power I could hear a clear miss in one cylinder very similar to the sound when I lost a plug. I taxied back to the hangar, shut off the fuel and switched off mags.
Once I pulled it back in and removed the cowling the problem was all too easy to spot -- the gasket that seals the cylinder head to the base had failed:
 |
| Failed #3 Cylinder Gasket (Exhaust blew out this hole) |
Two of the nuts that hold down the head (studs come out of the head) were loose. I checked them all about 5 flying hours ago, so I'm not sure if they worked loose in that short a time or...? The hole caused the cylinder to lose all compression. In a barely 65 HP engine the loss of one cylinder is significant. The hot exhaust was also burning up the carb heat SCAT tubing.
Parts ordered and repairs to come...
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