[Walter Atkinson]

Kevin:

Thank you for that link. There is some misinformation in it I'd like to address. To wit:

1) Someone said that during an in-flight mag check that EGTs and CHTs would rise. During any mag check and especially LOP, the CHTs will fall when operating on one mag. Why? Because the thetaPP is occuring later and the intracylinder pressures are lower, therefore less heat is transferred into the head. This is not arguable. It can be observed by any of us. Simply WATCH the CHTs fall while on one mag. This means there is less stress on the engine during single mag operation. Try it an WATCH for yourself. CHTs will go down while on one mag. If you leave it there long enough, they will go down significantly.

2) The concern over de-tuning an engine if there is a dead mag is a red herring. It's not an operational issue. If it were, all of the twins used for training and all of the jump planes in the world would have detuned engines. This is one of those remarks made by an old wise mechanic that sounds so ominous that we dare not argue, but it's just not an operational issue. I asked several premier engine builders how often they have had to rebuild an engine because the crank counterweights were detuned and they looked at me like I was crazy. It sounds scary, but it's poppycock.

3) I have a turbocharged engine. I have no concern about doing in-flight mag checks on a TC'd engine. I do one right before the let-down on EVERY flight. I do them at between 85 and 90% power, LOP. That is most diagnostic. I know of about 700 pilots who do these routinely. One would think that if there were a bad problem being caused by this, SOMETHING would have shown up in at least one of these engines? So far, ZERO reports of any difficulty.

If anyone has any DATA to the contrary I would be very interested in looking at it.