From a friend with a Cirrus.  It uses the same engine as the Legacy.  Some clever detective work is needed.  Can anyone elucidate the problem?  Fred Moreno

Hi Fred – here is the entire saga regarding my mag problem.  If you or any of your fellow Lancair forum members have any insights – I would be really grateful!  I’ll email a copy of this to Walter Atkinson as well.

 

I bought my 2002 SR22 (IO-550N) with 700 hrs on it last year.  The logs indicated that the previous owner had opted to have both mags replaced with new ones in 2007 “in accordance with Bendix King’s 2000hr/4yr overhaul advice” – thinking that new is better, which may not always be the case as we now know!

The logs also indicated that the previous owner started having problems with mag timing since – visiting the shop every few months since then to have mag timing “checked”.  Due to continual problems the mags were again replaced in Nov 2008.

After buying the plane in April 2009, it first started having problems in Oct when I had a very rough ground mag check.  The E gap was “way off” and reset.  In December, on a long trip to Tasmania, I noticed CHTs running higher than normal, but put it down to the higher summer temps.  Upon returning, the mag timing was found to be off again, this time the shop queried lack of lubrication causing premature cam failure.  In February 2010, the mag timings again had to be reset, but the engineer (not my usual one) spotted that the mags were pressurized mags with the mesh gaskets (P/N 10-500556-101 instead of 10-500556-1 as specified).  It turns out the -101 pressurized mags were installed at the first replacement in 2007, and replaced with the same -101 pressurized mags in 2008 without anyone noticing the problem!  At that time we also dynamically balanced the prop down to IPS 0.009 @ 2563 rpm.

At annual inspection in April 2010, the timing was again found to be 6-8° advanced (L -18° & R-14°) and we decided to overhaul the mags – we found evidence of heat damage to both mags internally - ball bearings blue/black instead of silver and corrosion to the exterior of the capacitors, both of which tested OK.  At this stage I asked the shop to return the pressurized mags to normal status i.e. replace the mesh gaskets and reinstall the normal vent plug instead of the pin-hole plug used in the pressurized setup.

Since then I have flown 10+ hours but have noticed more vibration of the engine/airframe than previously.  The vibration is almost “teeth-chattering” at full power but reduces to “bearable” at 2500 rpm.

Also the inflight, high power LOP mag checks (2600rpm, 7500ft, 30-45°F LOP) have been “different” – my understanding is that the temp delta shouldn’t vary by much between mags on each cylinder:

 

 

The first rise is on the right mag, followed by the left mag.  I am not sure which mag is the problem one, there is no appreciable rough running on either mag, just that the EGTs on 2,4,6 are much higher than 1,3,5 on the right mag.   On the left mag - 2,4,6 are lower.  1 & 3 appear to be similar on both & 5 appears to be slightly higher on the left mag.

After first noticing this – I asked my engineer to recheck the timing and confirm that the mag overhaul was done to spec.  Timing was fine and the mags were indeed overhauled to spec.

Opinions please – do I still have a problem with my mags (do I need a second opinion or a new engineer)?  Or perhaps I have 3 failing plugs (Right mag – 2,4,6)?  Would this contribute to the vibration levels I am experiencing or should I look at the prop again (only been 3 months since last balance –  the only thing that’s changed is the mags!)

PS:  Attached is GAMI lean test – spread is 0.39, so pretty good and unlikely to cause the level of vibration I’m experiencing, right?  Also attached engine log file of last flight in case anyone’s interested.