Hi Andre',

I agree with everything that has been said and offer= a=20 couple more interesting experiences with my TSIO-550E, now with over 350=20 hrs.

At the 170 hr mark I had a complete Mag. failure on=20= the=20 preflight run up. This was after a previous day 2:15 hr. flight at FL 240 an= d no=20 indication of a problem. After the canceled flight and opening up the first=20= Mag.=20 We found that the Drain hole provided in the bottom of the pressurized chamb= er=20 was rusted closed and besides residual water being present the complete Mag.= was=20 destroyed from arcing. The casting holding the contacts was eaten away and b= lack=20 deposits were everywhere. That Mag. was replaced on Warrantee.

Then we looked at the second Mag. It looked fine and= on=20 closer examination it looked like the water drain hole was larger by about t= wice=20 the size. Also, I looked at the "in line water filter/ separator" or what ev= er=20 they call it. It was mounted from the factory with an Adel clamp around it.=20= That=20 allowed it to slide backwards to where the drain orifice was now not at the=20= low=20 point, however, there was no water in this filter. I put a tie rap around th= e=20 rear hose boss to lift the rear and lower the front where the drain would be= come=20 the low point as intended.

I'm not sure whether the filter was any part of the=20 problem but the drain hole in the new Mag. was much larger in the=20= new=20 Mag. than the old, and water was the problem. I am due to inspect them again= and=20 I understand that in Cessna 414/421's there is a service bulletin to do this= =20 inspection every 100 hrs. I'm a believer and highly recommend this to everyo= ne.=20 This easily could have caused a momentary back fire or a missed fire as Geor= ge=20 suggested. And as an engineer I would also strongly suspect electrical probl= ems=20 first when you have a miss or backfire.

On another flight I forgot to turn on the Low Boost=20= at 10K=20 altitude like recommended and at 17 K the engine started to surge almost=20 violently before I could pull the power back. That is the condition I would=20 expect with a change of full flow or air in the fuel system. But I have hear= d of=20 Lumpy gas before also. This mostly fits in Mud Pen where we engineers spend=20= some=20 of our time. My complements to BRENT, ROBERT, GEORGE, and all those much sma= rter=20 than me. All disclaimers invoked you all.=20

Jim Hergert
N6XE (An=20 Sexy)