ORIGINAL: David Gladwin

My Air World Hawk has undergone final systems checks before flying. I noticed that during the engine runs there were some absolutely minute air bubbles going to the engine (Wren XL 200 which runs beautifully, cool and QUIET in the fully ducted installation ) which continued to run perfectly at all rpms. . I also noticed a small amout of air had accumulated in the header tank , all this despite checking EVERY component for leakage under pressure and vacuum and ditto the whole system installed. As there is no leakage in the system this air has to be coming from somewhere. As the pickups etc remained totally immersed in fuel theoretically there should be NO air in the system, so where is it coming from ? Could this be as a result of aeration of the fuel due to slight cavitation in the refuelling pump (Kavan).

Components: Airworld 4L glass tank, checked underwater for leaks.
Orbit type clunk.
Header: Jet A1 4 oz centered tank with pleated paper pick up, no leakage.
Festo fittings all OK with square cut tubing, no leakage. (and Festo fittings are contrary to what I frequently hear, designed and approved for use at up to 1 bar vacuum )

I dont think the small amout of air is likely to cause a flameout but I am intrigued that the sytem is not TOTALLY air free. Any theories or explanations, gentlemen ?

Regards, David Gladwin.