Yes I was thinking wrong as I'm speaking of engine filters indeed. However, I don't recall IDG filters having the same safety built in, nor do I see the need of it. You screw up the IDG of course, but that's why the disconnect feature is there. If it can be of any clarification: we once had a teared IDG filter, so some of the oil was bypassing the filter, and we had to change IDG and oil coolers in the system. So I think it's possible to run the IDG without filter, but if there is any particles in the system, everything is to be written off.