varios not using a total energy probe

"Mike Borgelt" wrote in message

What pitot/static positions are you using? I presume nose and sides
of the nose. Some people run pitot static TE off tail fin mounted
pitot static probes which are no better than a TE probe on the fin and
maybe worse for the above reasons and the one below.

Two static ports on the side of the nose just forward of the instrument
panel. The pitot is in the nose vent.


If you do pitot/static TE you want the pitot to be twice as far from
the C of G as the static port and on the same side. This avoids
pressure transients due to atmospheric pressure gradient during pitch
manouvers. Stig Oye pointed this out to me 20 years ago.

Possibly the static ports are a bit further forward than half the distance
from the CG to the nose pitot.


The B40 has electrically adjustable instrument time constant. See the
manual but VERRRY gently on the adjust please! Try about 20 degrees in
the faster direction if you like on the 180 deg trimpot. These are
factory set at the midway position and I haven't seen any reason to
change mine nor have I had people complain about the factory setting.

I'll probably take your advice and leave it alone. I often fly in rough air
with the buoyancy/shear ratio in the single digits and 30+ knots of wind
shear in the convective boundary layer. I'd hate to lose the silky smooth
response. The onset of lift is pretty obvious with the stiff carbon wings
on the Nimbus. With softer wings, the vario delay wouldn't be noticeable.

That's interesting what you said about the Nicks TE probe on the nose. Has
anyone tried that?

Bill Daniels

On Fri, 23 Apr 2004 01:06:40 GMT, "Bill Daniels"
wrote:

rs ago.

Possibly the static ports are a bit further forward than half the distance
from the CG to the nose pitot.

Probably close enough. The maths is simple.

For a TE vario you want pressures so:
static - q
This can be generated as (2 x static) - pitot
pitot = static + q
If you pitch so at the static port you see decrease of delta p then at
the pitot you see 2 x delta p if the pitot is twice as far from the C
of G as the static port, put these in the TE equation and they cancel
hence no transient pressure.


The B40 has electrically adjustable instrument time constant. See the
manual but VERRRY gently on the adjust please! Try about 20 degrees in
the faster direction if you like on the 180 deg trimpot. These are
factory set at the midway position and I haven't seen any reason to
change mine nor have I had people complain about the factory setting.

I'll probably take your advice and leave it alone. I often fly in rough air
with the buoyancy/shear ratio in the single digits and 30+ knots of wind
shear in the convective boundary layer. I'd hate to lose the silky smooth
response. The onset of lift is pretty obvious with the stiff carbon wings
on the Nimbus. With softer wings, the vario delay wouldn't be noticeable.

The big thing about varios is to get used to the response. That's why
I'm not fan of much user changeable vario response in the cockpit.
Wil Schuemann said this about 30 years ago and was right.

That's interesting what you said about the Nicks TE probe on the nose. Has
anyone tried that?

I've seen it done and used this on the ASW20B I flew at Uvalde in 1986
at the Nationals.
Worked Ok but the Texans used germ warfare on the Aussies there.

Mike

Watch out for that chile... It catches the unwary.

Mike Borgelt wrote:\
That's interesting what you said about the Nicks TE probe on the nose. Has
anyone tried that?


I've seen it done and used this on the ASW20B I flew at Uvalde in 1986
at the Nationals.
Worked Ok but the Texans used germ warfare on the Aussies there.

Mike

--

Pete