Cambridge 302 Question

[[email protected]]

I've have a Cambridge 302 in my glider. I have the setting at 0%
since I have the total energy probe fed into it, along with the pitot
tube and static port. The te tube is split just behind the cockpit as
recommended. The static and pitot are split or "t'd" behind the
instrument panel.

When I push hard forward to increase airspeed.....the cambridge VSI
goes up to 10knots positive.

Then when I pull back to bleed off airspeed.....the VSI goes down to
10 knots negative.

The manual says to increase the % , but doesn't say how much.

Another option is to not use the te tube and put it at 100%.

The te probe in my glider is located about 6 feet behind the wing spar
on the top of the fuselage. It's not the conventional spot on the
rudder.

Any thoughts? Recommendations?

[Gary Emerson]

wrote:
> I've have a Cambridge 302 in my glider. I have the setting at 0%
> since I have the total energy probe fed into it, along with the pitot
> tube and static port. The te tube is split just behind the cockpit as
> recommended. The static and pitot are split or "t'd" behind the
> instrument panel.
>
> When I push hard forward to increase airspeed.....the cambridge VSI
> goes up to 10knots positive.
>
> Then when I pull back to bleed off airspeed.....the VSI goes down to
> 10 knots negative.
>
> The manual says to increase the % , but doesn't say how much.
>
> Another option is to not use the te tube and put it at 100%.
>
> The te probe in my glider is located about 6 feet behind the wing spar
> on the top of the fuselage. It's not the conventional spot on the
> rudder.
>
> Any thoughts? Recommendations?

This may not be a factor at all, but if the tube is running under your
seat pan and is being squeezed by the underside of the seat pan, you can
get G induced inputs into the system. You push over and take the weight
off the tube, the tube expands which looks like big "up". You pull and
your weight sqishes the tube which looks like big "down". Not for sure,
but a possibility.

[Darryl Ramm]

On Apr 19, 1:51*pm, wrote:
> I've have a Cambridge 302 in my glider. *I have the setting at 0%
> since I have the total energy probe fed into it, along with the pitot
> tube and static port. *The te tube is split just behind the cockpit as
> recommended. *The static and pitot are split or "t'd" behind the
> instrument panel.
>
> When I push hard forward to increase airspeed.....the cambridge VSI
> goes up to 10knots positive.
>
> Then when I pull back to bleed off airspeed.....the VSI goes down to
> 10 knots negative.
>
> The manual says to increase the % , but doesn't say how much.
>
> Another option is to not use the te tube and put it at 100%.
>
> The te probe in my glider is located about 6 feet behind the wing spar
> on the top of the fuselage. *It's not the conventional spot on the
> rudder.
>
> Any thoughts? *Recommendations?

Yep, pretty easy. Normally you would just change the % compensation
until it behaves as you want. But then normally you would need little
if any electronic compensation.

You say it's a fuselage mounted probe, there is nothing wrong per se
with fuselage mounted TE probes, Dick Johnson spent time trying to
point that out.

Presumably you have a mechanical vario and capacity flask on the other
side of the split TE line. Does that mechanical vario seem to behave
correctly? If so the problem is at the Cambridge 302, and that 302
should not need huge compensation adjustments (normally none).

Check the plumbing carefully, it might be as simple as you actually
have the static and TE lines crossed at the Cambridge (that would be
the first thing to check - don't rely on the color or the tubing etc.
(it might be spliced wrong you cant' see) really check there is a air
pressure connection by blowing gently onto (not into!) the TE probe).

Also simplify the problem. Block off any ports you really don't need.
Check all connections carefully, etc. Block the other side of the TE
line where it splits. Double check that the IAS and pressure altitude
on Cambridge all look OK (long shot but it may show up a problems).

If you start to suspect the Cambridge, try just sticking it on the
static line with 100% compensation and see what it does. But this
really should not be needed.

Darryl

[[email protected]]

On Apr 19, 4:27*pm, Darryl Ramm > wrote:
> On Apr 19, 1:51*pm, wrote:
>
>
>
>
>
> > I've have a Cambridge 302 in my glider. *I have the setting at 0%
> > since I have the total energy probe fed into it, along with the pitot
> > tube and static port. *The te tube is split just behind the cockpit as
> > recommended. *The static and pitot are split or "t'd" behind the
> > instrument panel.
>
> > When I push hard forward to increase airspeed.....the cambridge VSI
> > goes up to 10knots positive.
>
> > Then when I pull back to bleed off airspeed.....the VSI goes down to
> > 10 knots negative.
>
> > The manual says to increase the % , but doesn't say how much.
>
> > Another option is to not use the te tube and put it at 100%.
>
> > The te probe in my glider is located about 6 feet behind the wing spar
> > on the top of the fuselage. *It's not the conventional spot on the
> > rudder.
>
> > Any thoughts? *Recommendations?
>
> Yep, pretty easy. Normally you would just change the % compensation
> until it behaves as you want. But then normally you would need little
> if any electronic compensation.
>
> You say it's a fuselage mounted probe, there is nothing wrong per se
> with fuselage mounted TE probes, Dick Johnson spent time trying to
> point that out.
>
> Presumably you have a mechanical vario and capacity flask on the other
> side of the split TE line. Does that mechanical vario seem to behave
> correctly? If so the problem is at the Cambridge 302, and that 302
> should not need huge compensation adjustments (normally none).
>
> Check the plumbing carefully, it might be as simple as you actually
> have the static and TE lines crossed at the Cambridge (that would be
> the first thing to check - don't rely on the color or the tubing etc.
> (it might be spliced wrong you cant' see) really check there is a air
> pressure connection by blowing gently onto (not into!) the TE probe).
>
> Also simplify the problem. Block off any ports you really don't need.
> Check all connections carefully, etc. Block the other side of the *TE
> line where it splits. Double check that the IAS and pressure altitude
> on Cambridge all look OK (long shot but it may show up a problems).
>
> If you start to suspect the Cambridge, try just sticking it on the
> static line with 100% compensation and see what it does. But this
> really should not be needed.
>
> Darryl- Hide quoted text -
>
> - Show quoted text -

I have all new tubing and new capacity flasks. The other two
mechanical VSI seem to work well. The cambridge works well
too....unless I push forward to speed up or pull back fast to slow
down.

Does the 100% compensation and the two static line system work ok?

SA

[Andy Melville[_2_]]

Sounds like s big leak in the system to me !
At 20:51 19 April 2009, wrote:
>I've have a Cambridge 302 in my glider. I have the setting at 0%
>since I have the total energy probe fed into it, along with the pitot
>tube and static port. The te tube is split just behind the cockpit as
>recommended. The static and pitot are split or "t'd" behind the
>instrument panel.
>
>When I push hard forward to increase airspeed.....the cambridge VSI
>goes up to 10knots positive.
>
>Then when I pull back to bleed off airspeed.....the VSI goes down to
>10 knots negative.
>
>The manual says to increase the % , but doesn't say how much.
>
>Another option is to not use the te tube and put it at 100%.
>
>The te probe in my glider is located about 6 feet behind the wing spar
>on the top of the fuselage. It's not the conventional spot on the
>rudder.
>
>Any thoughts? Recommendations?
>

[Andy Melville[_2_]]

Its a big leak in the system is my guess
At 20:51 19 April 2009, wrote:
>I've have a Cambridge 302 in my glider. I have the setting at 0%
>since I have the total energy probe fed into it, along with the pitot
>tube and static port. The te tube is split just behind the cockpit as
>recommended. The static and pitot are split or "t'd" behind the
>instrument panel.
>
>When I push hard forward to increase airspeed.....the cambridge VSI
>goes up to 10knots positive.
>
>Then when I pull back to bleed off airspeed.....the VSI goes down to
>10 knots negative.
>
>The manual says to increase the % , but doesn't say how much.
>
>Another option is to not use the te tube and put it at 100%.
>
>The te probe in my glider is located about 6 feet behind the wing spar
>on the top of the fuselage. It's not the conventional spot on the
>rudder.
>
>Any thoughts? Recommendations?
>

[[email protected]]

On Apr 19, 1:51*pm, wrote:
> I've have a Cambridge 302 in my glider. *I have the setting at 0%
> since I have the total energy probe fed into it, along with the pitot
> tube and static port. *The te tube is split just behind the cockpit as
> recommended. *The static and pitot are split or "t'd" behind the
> instrument panel.
>
> When I push hard forward to increase airspeed.....the cambridge VSI
> goes up to 10knots positive.
>
> Then when I pull back to bleed off airspeed.....the VSI goes down to
> 10 knots negative.
>
> The manual says to increase the % , but doesn't say how much.
>
> Another option is to not use the te tube and put it at 100%.
>
> The te probe in my glider is located about 6 feet behind the wing spar
> on the top of the fuselage. *It's not the conventional spot on the
> rudder.
>
> Any thoughts? *Recommendations?

Scott,

Go to screen 10 on the CAI 302 and note the indicated airspeed. You
may have the Pitot & static switched. Which mode are you in when this
happens climb or Cruise?

At TE probe requires that the Compensation be set at 0%. The Probe
supplies the Compensation.


Richard
www.craggyaero.com

[Darryl Ramm]

On Apr 19, 2:34*pm, wrote:
> On Apr 19, 4:27*pm, Darryl Ramm > wrote:
>
>
>
> > On Apr 19, 1:51*pm, wrote:
>
> > > I've have a Cambridge 302 in my glider. *I have the setting at 0%
> > > since I have the total energy probe fed into it, along with the pitot
> > > tube and static port. *The te tube is split just behind the cockpit as
> > > recommended. *The static and pitot are split or "t'd" behind the
> > > instrument panel.
>
> > > When I push hard forward to increase airspeed.....the cambridge VSI
> > > goes up to 10knots positive.
>
> > > Then when I pull back to bleed off airspeed.....the VSI goes down to
> > > 10 knots negative.
>
> > > The manual says to increase the % , but doesn't say how much.
>
> > > Another option is to not use the te tube and put it at 100%.
>
> > > The te probe in my glider is located about 6 feet behind the wing spar
> > > on the top of the fuselage. *It's not the conventional spot on the
> > > rudder.
>
> > > Any thoughts? *Recommendations?
>
> > Yep, pretty easy. Normally you would just change the % compensation
> > until it behaves as you want. But then normally you would need little
> > if any electronic compensation.
>
> > You say it's a fuselage mounted probe, there is nothing wrong per se
> > with fuselage mounted TE probes, Dick Johnson spent time trying to
> > point that out.
>
> > Presumably you have a mechanical vario and capacity flask on the other
> > side of the split TE line. Does that mechanical vario seem to behave
> > correctly? If so the problem is at the Cambridge 302, and that 302
> > should not need huge compensation adjustments (normally none).
>
> > Check the plumbing carefully, it might be as simple as you actually
> > have the static and TE lines crossed at the Cambridge (that would be
> > the first thing to check - don't rely on the color or the tubing etc.
> > (it might be spliced wrong you cant' see) really check there is a air
> > pressure connection by blowing gently onto (not into!) the TE probe).
>
> > Also simplify the problem. Block off any ports you really don't need.
> > Check all connections carefully, etc. Block the other side of the *TE
> > line where it splits. Double check that the IAS and pressure altitude
> > on Cambridge all look OK (long shot but it may show up a problems).
>
> > If you start to suspect the Cambridge, try just sticking it on the
> > static line with 100% compensation and see what it does. But this
> > really should not be needed.
>
> > Darryl- Hide quoted text -
>
> > - Show quoted text -
>
> I have all new tubing and new capacity flasks. *The other two
> mechanical VSI seem to work well. *The cambridge works well
> too....unless I push forward to speed up or pull back fast to slow
> down.
>
> Does the 100% compensation and the two static line system work ok?
>
> SA

All new tubing and all new capacity flasks probably leak more often
than all old tubing and all old capacity flasks that have not had all
new fingers poking around in them :-)

Three varios? The TE line is split three ways beyond the seat and the
two mechanical varios have their own capacity flasks right? The reason
for splitting beyond the seat is just to give some line impedance so
that the flow to/from the capacity flasks does not significantly
affect the direct pressure reading 302.

The electronic compensation and a static source works very well on a
C302. I use that on mine, it provides a separate vario independent of
the TE. However it is only as good as the static and pilot sources. I
know Cambridge (Dave Ellis?) previously argued that a good TE probe
was better than electronic compensation, but I can't tell the
difference.

However your ships seems to have something going wrong and instead of
just changing things I personally would work out what the problem is
first.

I had misread the direction of the vario change when you said you
pushed/pulled. So the other poster's suggestion that you have a big
leak may be more likely. Does the behavior of you speed up/slow down
test depend on the cockpit vents being full open of closed. If you
were flying with the vents mostly open, speeding up could raise
cockpit/fuselage internal pressure, causing a false climb indication.
Has a tube fallen off somewhere? Is a right angle or "T" adapter
cracked or fallen apart entirely. Are any lines blocked off, are the
stoppers really secure/airtight? Do you have something else
misconnected somewhere so that the TE line is actually open to the
ambient cockpit pressure. Have you checked the tube has not fallen off
the TE probe? Try making the circuit as simple as possible and remove
any split behind the seat (in case you have a huge leak in a capacity
or other vario case - unlikely though - if those other varios seem to
work - but it is not clear if they actually show a climb when they
should or if you are just saying they don't show false speed relate
readings). If they don't show a climb when they should you could have
a huge leak on the mechanical vario side that (in a stretch) could
explain this. Is there an alt static source behind the panel, is it
accidentally open? Is it plumbed in the correct line?

You may be too close to the problem. Have somebody else sanity check
what you have done and how you have debugged it. Be prepared to buy
them a beer when they walk straight up point out the "obvious"
error :-)


Darryl

[Darryl Ramm]

On Apr 19, 3:53*pm, wrote:
> On Apr 19, 1:51*pm, wrote:
>
>
>
> > I've have a Cambridge 302 in my glider. *I have the setting at 0%
> > since I have the total energy probe fed into it, along with the pitot
> > tube and static port. *The te tube is split just behind the cockpit as
> > recommended. *The static and pitot are split or "t'd" behind the
> > instrument panel.
>
> > When I push hard forward to increase airspeed.....the cambridge VSI
> > goes up to 10knots positive.
>
> > Then when I pull back to bleed off airspeed.....the VSI goes down to
> > 10 knots negative.
>
> > The manual says to increase the % , but doesn't say how much.
>
> > Another option is to not use the te tube and put it at 100%.
>
> > The te probe in my glider is located about 6 feet behind the wing spar
> > on the top of the fuselage. *It's not the conventional spot on the
> > rudder.
>
> > Any thoughts? *Recommendations?
>
> Scott,
>
> Go to screen 10 on the CAI 302 and note *the indicated airspeed. *You
> may have the Pitot & static switched. *Which mode are you in when this
> happens climb or Cruise?
>
> At TE probe requires that the Compensation be set at 0%. *The Probe
> supplies the Compensation.
>
> Richardwww.craggyaero.com

To be clear, you can adjust the compensation when using a TE probe.
Normally a small percentage to correct compensation issues, but
usually not needed. The manual appears to say you *must* use 0 when
using a TE probe. But this is wrong. And the manual also contradicts
itself and explains you can do this tweaking. But none of that is of
course related to the problem described here.

Darryl

[Darryl Ramm]

On Apr 19, 3:53*pm, wrote:
> On Apr 19, 1:51*pm, wrote:
>
>
>
> > I've have a Cambridge 302 in my glider. *I have the setting at 0%
> > since I have the total energy probe fed into it, along with the pitot
> > tube and static port. *The te tube is split just behind the cockpit as
> > recommended. *The static and pitot are split or "t'd" behind the
> > instrument panel.
>
> > When I push hard forward to increase airspeed.....the cambridge VSI
> > goes up to 10knots positive.
>
> > Then when I pull back to bleed off airspeed.....the VSI goes down to
> > 10 knots negative.
>
> > The manual says to increase the % , but doesn't say how much.
>
> > Another option is to not use the te tube and put it at 100%.
>
> > The te probe in my glider is located about 6 feet behind the wing spar
> > on the top of the fuselage. *It's not the conventional spot on the
> > rudder.
>
> > Any thoughts? *Recommendations?
>
> Scott,
>
> Go to screen 10 on the CAI 302 and note *the indicated airspeed. *You
> may have the Pitot & static switched. *Which mode are you in when this
> happens climb or Cruise?
>
> At TE probe requires that the Compensation be set at 0%. *The Probe
> supplies the Compensation.
>
> Richardwww.craggyaero.com

And that was a clever suggestion - pitot and static swapped and the
302 in cruise mode and configured to be a super netto or netto vario
so the indicator relies on the airspeed....

Note to Scott - the altimeter display on the 302 home screen has
nothing to do with the static plumbing, it senses cockpit ambient
pressure, so is cannot help debug this question. So try what Richard
suggests.

Darryl

[[email protected]]

On Apr 20, 12:05*am, Darryl Ramm > wrote:
> On Apr 19, 3:53*pm, wrote:
>
>
>
> > On Apr 19, 1:51*pm, wrote:
>
> > > I've have a Cambridge 302 in my glider. *I have the setting at 0%
> > > since I have the total energy probe fed into it, along with the pitot
> > > tube and static port. *The te tube is split just behind the cockpit as
> > > recommended. *The static and pitot are split or "t'd" behind the
> > > instrument panel.
>
> > > When I push hard forward to increase airspeed.....the cambridge VSI
> > > goes up to 10knots positive.
>
> > > Then when I pull back to bleed off airspeed.....the VSI goes down to
> > > 10 knots negative.
>
> > > The manual says to increase the % , but doesn't say how much.
>
> > > Another option is to not use the te tube and put it at 100%.
>
> > > The te probe in my glider is located about 6 feet behind the wing spar
> > > on the top of the fuselage. *It's not the conventional spot on the
> > > rudder.
>
> > > Any thoughts? *Recommendations?
>
> > Scott,
>
> > Go to screen 10 on the CAI 302 and note *the indicated airspeed. *You
> > may have the Pitot & static switched. *Which mode are you in when this
> > happens climb or Cruise?
>
> > At TE probe requires that the Compensation be set at 0%. *The Probe
> > supplies the Compensation.
>
> > Richardwww.craggyaero.com
>
> And that was a clever suggestion - pitot and static swapped and the
> 302 in cruise mode and configured to be a super netto or netto vario
> so the indicator relies on the airspeed....
>
> Note to Scott - the altimeter display on the 302 home screen has
> nothing to do with the static plumbing, it senses cockpit ambient
> pressure, so is cannot help debug this question. So try what Richard
> suggests.
>
> Darryl

If that turns out not to be the problem a simple pressure check for
leaks is in order.

9B

[[email protected]]

On Apr 20, 7:52*am, wrote:
> On Apr 20, 12:05*am, Darryl Ramm > wrote:
>
>
>
>
>
> > On Apr 19, 3:53*pm, wrote:
>
> > > On Apr 19, 1:51*pm, wrote:
>
> > > > I've have a Cambridge 302 in my glider. *I have the setting at 0%
> > > > since I have the total energy probe fed into it, along with the pitot
> > > > tube and static port. *The te tube is split just behind the cockpit as
> > > > recommended. *The static and pitot are split or "t'd" behind the
> > > > instrument panel.
>
> > > > When I push hard forward to increase airspeed.....the cambridge VSI
> > > > goes up to 10knots positive.
>
> > > > Then when I pull back to bleed off airspeed.....the VSI goes down to
> > > > 10 knots negative.
>
> > > > The manual says to increase the % , but doesn't say how much.
>
> > > > Another option is to not use the te tube and put it at 100%.
>
> > > > The te probe in my glider is located about 6 feet behind the wing spar
> > > > on the top of the fuselage. *It's not the conventional spot on the
> > > > rudder.
>
> > > > Any thoughts? *Recommendations?
>
> > > Scott,
>
> > > Go to screen 10 on the CAI 302 and note *the indicated airspeed. *You
> > > may have the Pitot & static switched. *Which mode are you in when this
> > > happens climb or Cruise?
>
> > > At TE probe requires that the Compensation be set at 0%. *The Probe
> > > supplies the Compensation.
>
> > > Richardwww.craggyaero.com
>
> > And that was a clever suggestion - pitot and static swapped and the
> > 302 in cruise mode and configured to be a super netto or netto vario
> > so the indicator relies on the airspeed....
>
> > Note to Scott - the altimeter display on the 302 home screen has
> > nothing to do with the static plumbing, it senses cockpit ambient
> > pressure, so is cannot help debug this question. So try what Richard
> > suggests.
>
> > Darryl
>
> If that turns out not to be the problem a simple pressure check for
> leaks is in order.
>
> 9B- Hide quoted text -
>
> - Show quoted text -

The pitot/static lines are correct. There is no leaks in the system.
All the lines and capacities are brand new now.

The Airspeed on page ten indicates correctly. It's within a couple
knots of the mechanical airspeed indicator adjacent to the cambridge.

My question is, how much %? The manual address this issue by
stating..."increase the % if this is happening".....but doesn't say
just how much.

I guess I can just try 10%, then 20%, then 30% and so forth. But
would much rather have a more educated attempt at setting this the
right way.

[John Cochrane]

In addition to good advice from others, I'd start by taking the
mechanical vario off the system. The 302 is very fussy about sharing
lines with other instruments, and flow-based varios in particular. Get
the 302 working right on its own, then see if you can add the other
one back without making the 302 work worse. Also leak check the pitot
and static too. I had weird 302 problems twice that came down to leaks
in the ASI and ASI tubing.

John Cochrane

[Darryl Ramm]

On Apr 20, 6:38*am, wrote:
> On Apr 20, 7:52*am, wrote:
>
>
>
> > On Apr 20, 12:05*am, Darryl Ramm > wrote:
>
> > > On Apr 19, 3:53*pm, wrote:
>
> > > > On Apr 19, 1:51*pm, wrote:
>
> > > > > I've have a Cambridge 302 in my glider. *I have the setting at 0%
> > > > > since I have the total energy probe fed into it, along with the pitot
> > > > > tube and static port. *The te tube is split just behind the cockpit as
> > > > > recommended. *The static and pitot are split or "t'd" behind the
> > > > > instrument panel.
>
> > > > > When I push hard forward to increase airspeed.....the cambridge VSI
> > > > > goes up to 10knots positive.
>
> > > > > Then when I pull back to bleed off airspeed.....the VSI goes down to
> > > > > 10 knots negative.
>
> > > > > The manual says to increase the % , but doesn't say how much.
>
> > > > > Another option is to not use the te tube and put it at 100%.
>
> > > > > The te probe in my glider is located about 6 feet behind the wing spar
> > > > > on the top of the fuselage. *It's not the conventional spot on the
> > > > > rudder.
>
> > > > > Any thoughts? *Recommendations?
>
> > > > Scott,
>
> > > > Go to screen 10 on the CAI 302 and note *the indicated airspeed. *You
> > > > may have the Pitot & static switched. *Which mode are you in when this
> > > > happens climb or Cruise?
>
> > > > At TE probe requires that the Compensation be set at 0%. *The Probe
> > > > supplies the Compensation.
>
> > > > Richardwww.craggyaero.com
>
> > > And that was a clever suggestion - pitot and static swapped and the
> > > 302 in cruise mode and configured to be a super netto or netto vario
> > > so the indicator relies on the airspeed....
>
> > > Note to Scott - the altimeter display on the 302 home screen has
> > > nothing to do with the static plumbing, it senses cockpit ambient
> > > pressure, so is cannot help debug this question. So try what Richard
> > > suggests.
>
> > > Darryl
>
> > If that turns out not to be the problem a simple pressure check for
> > leaks is in order.
>
> > 9B- Hide quoted text -
>
> > - Show quoted text -
>
> The pitot/static lines are correct. *There is no leaks in the system.
> All the lines and capacities are brand new now.
>
> The Airspeed on page ten indicates correctly. *It's within a couple
> knots of the mechanical airspeed indicator adjacent to the cambridge.
>
> My question is, how much %? *The manual address this issue by
> stating..."increase the % if this is happening".....but doesn't say
> just how much.
>
> I guess I can just try 10%, then 20%, then 30% and so forth. *But
> would much rather have a more educated attempt at setting this the
> right way.

Electronic adjustment to TE compensation when I've tried it is a few
percent at most. TE probes should work very well. What you are
describing sounded like a significant problem, not something you tweek
electronic compensation to a TE for. You seem to be confident you
don't have any problems - you know you have no leaks - you have done a
leak-down test on all the lines? All your mechanical varios work
correctly right? They show climb etc. when they readings and readings
match (and they have separate capacities T-ing off behind the seat...
if they don't match then that might help show if one of the varios
themselves are leaking etc.)...

Have somebody else check your work. Try the static line at 100%
compensation. If that does not work send the 302 to Cambridge for
repair or try swapping with another to see if that works.

Darryl

[[email protected]]

On Apr 19, 1:51*pm, wrote:
>
> When I push hard forward to increase airspeed.....the cambridge VSI
> goes up to 10knots positive.
>
> Then when I pull back to bleed off airspeed.....the VSI goes down to
> 10 knots negative.
>

To answer you question directly - I don't believe you can fix the
problem you describe with electronic compensation. Here's why:

If I remember correctly an uncompensated vario reads climb when you
bleed off airspeed and sink when you accelerate. This is because with
static pressure only as the pressure source (no compensation) your
vario will indicate the altitude change irrespective of any associated
change in kinetic energy. Your description reads like the opposite, or
OVER-compensation.

I believe there also is an effect from the initial drag of adding lift
in a pullup (and presumably the opposite from reducing lift in a push-
over maneuver). That causes the uncompensated vario to show some small
altitude loss at the very beginning of a hard pullup (think of the
glider "mushing" a bit when you pull hard). This means that on a hard
pullup the vario would read momentarily down by 1 knot or so, then
read up until the speed stabilizes - all in still air, of course.

Putting this second effect aside for now, a pullup from 100 knots down
to 60 knots will gain you about 250 feet in about 10 seconds -
depending on the steepness of the pullup. That translates to 15 knots
average climb rate. You will see more climb rate early in the pullup
than at the end. If you were reporting 10 knots of positive climb rate
on a pullup then it would lead me to believe that you are getting
little or no total energy compensation and you should set the CAI 302
to 70% or so. This has two problems: First, you are reporting behavior
that indicates 70%+ OVER-compensation, not under. Second, I'd be hard-
pressed to recommend to someone that they put that much electronic
compensation on top of a TE probe since you are likely masking a big
problem.

Finally, you are asking for a specific answer to an insufficiently
defined problem. Without knowing the pullup profile the fact that you
are showing 10 knots on the vario doesn't really give enough
information to know how to set your instrument. I generated an answer
by assuming a profile - but I don't really know what kind of pullup
you used to generate this result. The glider matters too, but my
analysis ignores this detail in favor a of a simple energy conversion
relationship.

Hope that's helpful.

9B

[[email protected]]

On Apr 20, 9:09*am, wrote:
> On Apr 19, 1:51*pm, wrote:

> I generated an answer
> by assuming a profile - but I don't really know what kind of pullup
> you used to generate this result. The glider matters too, but my
> analysis ignores this detail in favor a of a simple energy conversion
> relationship.

Oh, and I generated an answer also based on the assumption that your
vario is behaving in a manner opposite to what you described - unless
I missed something in college physics.

9B