Hi all,

Eventually after many test and changes the mystery has been solved. My turbine now starts, runs and go to maximum rpm as it should, without starting a kero fire after starting. During the past few weeks many of the industry experts assisted and I wish to thank each and everyone who made constructive suggestions.

In short and without going into the scientific why's and wherefores I will explain the conclusions and outcomes we've arrived at. I will not bore you with the calculations that helped prove my problem.

Basically, the reason I was getting fire after start, when running up the turbine to full power - was because the venturi effect from the exhaust flow into the thrust pipe was so strong, that air was being drawn around the turbine (inside the bypass) and starving the turbine from air on the intake side (in front) of the turbine. Why then is this not the case with my other two identical installations? The only difference between my three jets is the volume of available air in front of the turbine. The problem jet has the smallest intakes and between 30 and 50% less air in front of the turbine.

So how to overcome the problem? First, by opting for (what I thought) a generous gap around the turbine, I actually made it worse. If I cut the gap from 12mm to 6mm then the venturi effect is less and less air is 'robbed' from the front of the turbine. Second, and this is what I've done (as confirmed by my friend with his Hawk) I provided more air at the rear of the turbine which could be drawn by the venturi effect, without having to draw air from the front of the turbine - I now have a 25 x 100mm cutout in the top cover of the hatch and have also opened up all the scale intakes in the fuselage. It is actuall amazing to feel how much air is being pulled into the fuselage through all these new openings, when the turbine is running.

So no more stalling turbine (the technical name for what was happening in my situation).

Hope my experience will help anyone having similar problems in future, when using a bypass.

Cheers,

Jan