Cambridge 302 problem..HELP Please

On Jun 25, 8:50*am, T8 wrote:
On Jun 24, 10:45*pm, David Prather

wrote:
I have the same problem-- tremendous "lift" starting at 80 kts. I am
trying to share the TE connection with a mechanical Winter vario that
works with a capacity flask. Does anyone else share TE between a
mechanical vario and the 302?

-David Prather

David -

302 works best with dedicated TE and static ports. *Excess volumes in
the systems (capacity vario, asi, altimiter) play hell with pressure
transducer instruments like 302. *TE can be shared, with some loss of
performance. *As previously noted, the closer the "tee" is to the
probe, the better. *I would suggest test flying with dedicated ports,
then work from there to a compromise that works for you. *Pitot may be
shared with asi.

As far as anomalous "lift" indications in cruise, obvious things to
check were covered -- correct connections, no leaks (including probe
socket o-rings), correct polar in 302, correct ias showing on 302.

Electronic compensation is fraught with difficulties (chiefly that is
extremely sensitive to *small* pneumatic errors in both magnitude and
timing) and never recommended as a preferred approach.

-Evan Ludeman / T8

Edit: "TE can be shared with a capacity type vario, with some loss of
performance". But don't put the tee close to the instruments if you
do this!

All ports may be shared with other pressure transducer type
instruments, without loss of performance. Tee location not critical
in this case.

-T8

Thanks to all for the help.
The polar was set incorrectly.
I really appreciate everything.
bob holliday
At 03:18 25 June 2009, Darryl Ramm wrote:
On Jun 24, 7:45=A0pm, David Prather
wrote:
I have the same problem-- tremendous "lift" starting at 80 kts. I am
trying to share the TE connection with a mechanical Winter vario that
works with a capacity flask. Does anyone else share TE between a
mechanical vario and the 302?

-David Prather

At 15:00 22 June 2009, Robert Holliday wrote:

My 302 seems to work OK at 60 knots but when i fly 80 knots it
indicates
10
knots lift (it is set up for super netto). The total energy is set at
0%
as
per instructions. It is not set up for electronic compensation. I
checked
for leaks in the TE probe and tubing and found none. I just had it
upgraded to the USB port and the software fixed so it would not
"fill
up" the flight log storage. Has anyone had this kind of problem? any
ideas?
thanks.
bob holliday



Share the TE line? Hopefully not joined close by. One of the leading
claims to fame of the C302 is it is a direct reading variometer. It
digitally measures pressure and calculates the rate of change, it is
not measuring air flow to/from the capacity like with a vane based
vario. If you have both on that TE line split the line well away from
the instruments so there is some impedance in the line so the flow to
the flask does not screw up the C302 entirely. The standard
recommendation is to split back behind the seat area and run two lines
up to the panel.

You can also just put the C302 on the static port (esp. if you have a
tripe probe) and use electronic compensation. I know Dave Ellis
claimed a good TE probe should be better, but the electronic
compensation works great for me. That also provides you some
redundancy between a problem in the TE line talking out both varios.

Darryl