Hi Andre',

I agree with everything that has been said and offer a couple more interesting experiences with my TSIO-550E, now with over 350 hrs.

 

At the 170 hr mark I had a complete Mag. failure on the preflight run up. This was after a previous day 2:15 hr. flight at FL 240 and no indication of a problem. After the canceled flight and opening up the first Mag. We found that the Drain hole provided in the bottom of the pressurized chamber was rusted closed and besides residual water being present the complete Mag. was destroyed from arcing. The casting holding the contacts was eaten away and black deposits were everywhere. That Mag. was replaced on Warrantee.

 

Then we looked at the second Mag. It looked fine and on closer examination it looked like the water drain hole was larger by about twice the size. Also, I looked at the "in line water filter/ separator" or what ever they call it. It was mounted from the factory with an Adel clamp around it. That allowed it to slide backwards to where the drain orifice was now not at the low point, however, there was no water in this filter. I put a tie rap around the rear hose boss to lift the rear and lower the front where the drain would become the low point as intended.

 

I'm not sure whether the filter was any part of the problem but the drain hole in the new Mag. was much larger in the new Mag. than the old, and water was the problem. I am due to inspect them again and I understand that in Cessna 414/421's there is a service bulletin to do this inspection every 100 hrs. I'm a believer and highly recommend this to everyone. This easily could have caused a momentary back fire or a missed fire as George suggested. And as an engineer I would also strongly suspect electrical problems first when you have a miss or backfire.

 

On another flight I forgot to turn on the Low Boost at 10K altitude like recommended and at 17 K the engine started to surge almost violently before I could pull the power back. That is the condition I would expect with a change of full flow or air in the fuel system. But I have heard of Lumpy gas before also. This mostly fits in Mud Pen where we engineers spend some of our time. My complements to BRENT, ROBERT, GEORGE, and all those much smarter than me. All disclaimers invoked you all.

 

Jim Hergert
N6XE (An Sexy)