I flew for the first time in -11deg C weather today, and came across a phenomena that I'd like to understand.
Conditions:
C182Q
Temp/DewP: -11/-18 C
The plane had flown earlier in the day, and was parked in a non-heated hangar, but was not plugged in.
I successfully was able to start the engine with 4 primer strokes. However it would quit again withing ~10 sec unless I was ready for another primer stroke. It took about one minute before the engine was warm enough to run by itself.
With all that priming, I wasn't surprised when my right mag turned up weak in the runup. I tried what I did many times before in warmer weather: run the engine up to ~2200RPM and start leaning aggressively in an attempt to burn off the spark plug fouling.
But this didn't work: To my big surprise the mixture setting was unstable at the lean end, i.e. if I pulled the mixture a little more, the RPM dropped dramatically, and didn't recover when I put the mixture back to where it was. I had to go almost full rich for the RPM to recover. Of course this prevented getting a clean burn-off. I eventually got the mixture check to within 200RPM, and decided to fly. After the flight I repeated the run-up, and the mag was just fine.
What bugs me is that I do not understand this unstable mixture behavior. Is that something known and/or normal? What causes it? I never observed it in warmer weather.
Conditions:
C182Q
Temp/DewP: -11/-18 C
The plane had flown earlier in the day, and was parked in a non-heated hangar, but was not plugged in.
I successfully was able to start the engine with 4 primer strokes. However it would quit again withing ~10 sec unless I was ready for another primer stroke. It took about one minute before the engine was warm enough to run by itself.
With all that priming, I wasn't surprised when my right mag turned up weak in the runup. I tried what I did many times before in warmer weather: run the engine up to ~2200RPM and start leaning aggressively in an attempt to burn off the spark plug fouling.
But this didn't work: To my big surprise the mixture setting was unstable at the lean end, i.e. if I pulled the mixture a little more, the RPM dropped dramatically, and didn't recover when I put the mixture back to where it was. I had to go almost full rich for the RPM to recover. Of course this prevented getting a clean burn-off. I eventually got the mixture check to within 200RPM, and decided to fly. After the flight I repeated the run-up, and the mag was just fine.
What bugs me is that I do not understand this unstable mixture behavior. Is that something known and/or normal? What causes it? I never observed it in warmer weather.