Marc,
I spoke to an instructor about the issue of doing mag checks at 100% with friction on. He made the distinct difference between control locks (no movement posible) and control frictions (posible, just more force needed). So his point of view was that, yes the machine is 'live' so to speak, but in the unlikely case of the machine wanting to do something on its own, that pilot control is there, albeit with much larger control forces. He believed that if there was any real problem on this point, then it would need to be clearly stated in the POH not to perform mag checks at 100% with frictions on (although also recognising that POHs are not perfect). In fact one of his students once took off with frictions on and after putting in an order for new underwear, safely landed the machine, something that would have been impossible with control locks.
Also as an aside, he thought that doing a Mag check at 75% has the added advantage in that if something is wrong with the engine, you get a chance to discover it a lower RPM and thus may potentially damage the engine less than discovering it at 100%. He didn't want to give it too much importance, considering it an unlikely scenario. The important thing was to do the mag check properly whichever RPM you decided to do it at.
So my conclusion to all of this is that I will continue to do a mag check at 75%, not too much to do while the engine is warming up anyway (asuming one has done one's homework already) and do another one at 100% to double check.
Cheers!
Irlandés
