Hi folks. Got a little more insight on leakdown testing to pass along.
I think my last offering on the subject may have been incomplete.
A family member in CA is a dedicated private pilot with a Beechcraft
Bonanza. He follows his plane's FAA maintenance very closely. He
stated that FAA regulation periodic inspection of piston engine
cylinders calls for leakdown testing only, the two-gauge system only.
With the air-line gauge at 80 psi, the cylinder gauge must not be less
than 45 psi. He said his Bonanza's cylinders at last test showed 55 to
60, which passed. I had a ride in the plane and it ran like a charm.
This 45/80 means 44% leakdown. My Ardun's cylinders show 9 - 19%
leakdown. Ardun Doug told me the other day his numbers on the Ardun
that just took the 210 mph Modified Roadster record at Bonneville are a
little better than that, but he has found that if you rock the pistons a
little at the top dead center position with a wrench on the crank, you
may get a better leakdown figure because minute changes in the lay of
the rings in relation to piston and cylinder make a difference.
Just a little tidbit for the theoreticians amongst us.
Cheers from ArdunBill in the Great Dismal Swamp, Chesapeake, VA
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