On 01/17/07 08:54, Roy N5804F wrote:


"Mark Hansen" wrote in message
...
On 01/17/07 08:35, Roy N5804F wrote:

Dave,

I have signed up !

About the only instrument that I have not overhauled in this Archer is
the
VSI.
It reads horribly optimistic, like, I have the only Archer ever built
that
climbs on the plains here at 1200 FPM.
If I really try, I can make 1500 FPM :-)

I have to admit that I don't know much about the operation of a VSI
appertaining to an Archer :-(
I can't get my head round it at the moment, but could the slight negative
pressure in the cabin affect the VSI ?

It shouldn't. The VSI should be vented (through a calibrated "leak") to
the static air source, outside. The cabin pressure shouldn't affect it,
unless you've selected the alternate static source, or there is a leak
between the static source and alternate static source.

Thanks,
I had all the hoses replaced last year, incluing all in the cockpit and out
to the pitot tube.
Maybe they are all ok.
[I changed all the vacuum hoses as well]

Well ... one way to tell would be to select the alternate static source
while flying. Assuming your alternate static source is vented to the
cabin, it should show a slight climb for a time before settling back
to zero.

If it shows no change when selecting the alternate static source, there
may be something amiss there.

--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA