Cleared the ground for a brief period today. As far as the airplane is concerned, everything is good. CG seems to be right on the spot. Much better as it was 12 years ago at the first flight with the SOOB.

Here is the reason why it was not a flight. A few days ago when I started high speed taxi, as soon as it picked up air speed, the engine started to sputter and almost cut out totally. This was at the same RPM as at a run up, where it does not do that. With a wiggly tail dragger as the Avid is, there was no way reading enough instrument for making a preliminary analysis. I recorded the instrument panel with a GoPro at 2sec intervals.

Looking at the first pictures, the answer came up right away, increasing pressure under the cowl where the intake for the engine is located. Like the EGT shot up over 1600 just before the sputtering started. Since my radiator air is going to the outside of the cowling, there was no impact on cooling. Btw cooling is really good. At an OAT of 95F, oil and water stayed at around 170F no matter what I did.

 

For todays runs, I taped the inlet around the prop hub shut. Sure enough, the sputtering occurred at higher airspeed, and was not as total, however, EGT was still going to around 1600.

 

The conclusion is, I have to open the cowling exits a lot.

 

Richard Sohn
N2071U

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