In-flight ignition misfire procedure

Jamie · #1 05-12-2009, 01:57 PM

Let's assume that you're airborne and notice (via your engine monitor) that one of your cylinders is not firing on one of your mags/EI. I had this scenario happen once when I had a fouled plug. The mag run-up was fine before take-off, but I guess the plug fouled after the run-up (I had an extended hold after doing my runup). In my case I detected the issue by noticing several anomalies on my engine monitor (higher FF, #2 peaking before #3, etc). I did an in-flight mag check and sure enough it was running rough on one mag.

Anyway...what is the correct procedure in this situation? Should you continue to fly off of both mags or just the non-offending mag?

frankh · #2 05-12-2009, 04:08 PM

I can't see why you wouldn't just continue to run on both mags.

All that will happen is the effective timing on the one cylinder will be retarded and thus slightly less efficient (this assumes you have 2 EI's or 2 mags..Both normally fire together) on the that one cylinder.

Seeing as no two cylinders ever fire at the same time the engine doesn't care. You might as well have the better efficiency on the remaining 3 cylinders rather than limit the timing of all 4 cylinders by turning off the offending ignition.

Now if you have one mag and one EI then the same thing happens except it will be less noticable if the offending plug is on the mag.

Frank

Jamie · #3 05-13-2009, 05:31 AM

Yeah Frank, that's pretty much what I was thinking. I was just curious because I have read conflicting things.

Geico266 · #4 05-13-2009, 06:35 AM

Are you leaning on the ground while taxing & holding? I realize this was a one time event, but a different ground technique may have prevented it?

Jamie · #5 05-13-2009, 07:00 AM

Quote:

Originally Posted by Geico266

Are you leaning on the ground while taxing & holding? I realize this was a one time event, but a different ground technique may have prevented it?

Yes, I religiously lean on the ground. I was ready to launch so I had already gone mixture full rich, heard a crackle on the radio, then a short final call, and then watched an L-39 proceed to do multiple 250kt passes down a different runway that the winds were clearly not favoring. The runways were intersecting and he was making midfield downwind (the upwind of the runway I was waiting at) in 20 seconds flat.

So basically I was stuck there until he finished playing. I should have leaned it back out. That's the only time I have had any fouling. Also, the plug needed to be gapped (which I did of course) so that may have aggravated the situation.

frankh · #6 05-13-2009, 08:46 AM

Radio call might have been in order...Like "Hey there are other airplanes trying to use this airport if you don't mind rich boy!"...

Kahuna · #7 05-13-2009, 07:18 PM

Quote:

Originally Posted by Jamie

Should you continue to fly off of both mags or just the non-offending mag?

Both.........

az_gila · #8 05-13-2009, 08:23 PM

Quote:

Originally Posted by Kahuna

Both.........

...which ever option was smoother, providing no loss of rpm's....