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Hi
Ed;
This talk of stalled props brings up another question. Last
week when I was doing circuits, on one of the touch & goes, moments after
I'd applied power, the engine suddenly revved up momentarily much the same way
as when you hit a patch of ice while driving a vehicle with a heavy foot. This
happened very fast so I wasn't able to check the RPM (sure wish I had a
datalogger), but both my buddy & I heard/felt it. My first thought was the
PSRU had slipped, but it had no accompanying mechanical noise (like broken
gears) then second thought was prop stall. I held it on the ground a little
longer without reducing power, but as we pulled through 90mph with no further
indication of a problem ( I still had several thousand feet of runway ahead of
me) I let her lift off and then went on to complete another dozen circuits with
no further incidents. But afterwards we discussed it further and I recalled
Dave's broken PSRU shaft, but if I recall his was a clean break without any sort
of preceding slip. This just leaves a prop stall as the likely culprit, but I
wouldn't expect that a prop would stall when at approx. 50mph. At the time my
electronic prop governor was on auto and had been performing well and in any
case the electric IVO prop is too slow to have gone full fine momentarily so I
can almost discount this as being related.
Any thoughts on whether this could have simply been a
momentarily stalled prop?
Todd
Interestingly enough before I had the prop shortened, I
was a Tracy Crooks and was doing a run up to get some exhaust sound
readings. It was a cool morning and the engine was turning around
5800-6000. Tracy and I (as well as the sound meter) could hear the prop
blade stalling and unstalling (apparently as the blade rotate different
orientation with respect to the cowl and effect the airflow enough to cause it
to stall and that point and then recover). You could hear a distinct
"wop! wop! Wop!" sound as the prop stalled and unstalled.
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