ORIGINAL: Woketman
For many years I have used the 6 mm Festo filter in all orientations. I used to worry about the big air bubble that you can clearly see that resides in the filter. As you, I worried that it could dislodge and flame out the turbine. I would try different orientations, shaking it, etc. Nothing I have ever done could make that bubble leave the filter.
Bottom line is this: for the Festo filter, orientation does NOT matter one bit. Just install and fly.
Use the Festo and you don't have to worry about purging air bubbles.
I have perhaps 1/100th the experience of most of you here and am hesitant to disagree, but for SOME reason my results with this exact filter are exactly to the contrary. Big bubble, turn the filter vertically, bubble left, engine burped (but did not quit).
Sorry, Woket....I saw what I saw and once was enuff to make me a believer in others' advice to use loose and vertical mounting.......