The Lyco procedure includes leaning in order to reduce the mag drop. It isn’t LOP; it is just a slight lean, just a bit back from full rich which is where the mag test is normally done (at 2000rpm).
So it is an acceptable procedure.
Whether the need for it indicates a faulty or mis-adjusted mag, I don’t know. I know the cause of the mag drop (obviously, only one plug firing) but I don’t understand the factors in the magneto which would affect its magnitude. Especially if it is identical on both mags.
Peter wrote:
improved from some 200rpm
200rpm should be a concern already 
As far as I remember on run-up, mags check, each mag should not drop more than 150rpm unless you play with LOP on the ground.
More information about LOP on the ground here
I am informed that the coils are tested under heat, on a mag overhaul. I didn’t know that.
vic wrote:
My guess – sorry for being a bit paranoid on this topic – the mag coil is close to be scrap.
Yep, sounds plausible. Had exactly that in a C210 right in the middle of Australia – Birdsville.
Hmmm, yes, could well be. Very interesting.
Thankfully that magneto is now history, and going back to the US for an overhaul. We did a service right after the said flight and the A&P/IA reckoned the impulse coupling didn’t sound right. It was also a bit sticky when rotated by hand. So I put in a spare mag (D3000 single shaft one; can never be too paranoid in this case) and the difference is dramatic in the mag drop amount; improved from some 200rpm (and in spec only if leaning IAW the Lyco instructions) to 120rpm at full rich.
I wonder if any bench test can reveal this? The mags are not tested at an elevated temperature.
Peter wrote:
2 people noticed it.
Funny enough, I get ear decompression at same altitudes as my partner
Peter wrote:
On a recent flight of about 6hrs, 1hr before landing
Maybe it was eating some fuel dirt? The last hours may show some rough engine running either from dirt/water in fuel or simply fluid imbalance in the wing (unless fuel pump is ON or you have aerobatics fuel tanks)? tough if you had a dry run with air/fuel mix it is very noticeable
Interesting that somebody has an SOP for this
Yes I think it took under the 5 seconds which is the EDM700 sample rate.
Sounds like our Grob115E drill for a blocked nozzle (strong but uneven running)
Mixture…Rich
throttle….Full for 5 secs
Subsequently reset best power mixture and throttle setting
I’m guessing sample rate didn’t pick up on the data?
Just went rich. There wasn’t enough time to really think about it, and the symptom was close to what you get if you over-lean.
