Multiple varios

On Saturday, December 30, 2017 at 9:57:00 AM UTC-8, wrote:
Actually, I find the second vario quite useful. In straight flight I have my V-7 set on netto, but when there's a mild surge it's always a question, is this an actual thermal or just a change in air movement? The Winter tells me right away, and I can make a quick decision: turn or keep going.

A Winter variometer cannot tell you anything "straight away".

Maybe not in real life, but in the lab (or the workshop) the response of a Winter vario can be much faster than more modern instruments based on pressure transducers.

The video at https://www.youtube.com/watch?v=XmgH...ature=youtu.be shows the response of a Winter variometer and an LX 5000 connected to the same TE line. The pressure is quickly reduced by about 1 hPa, and the variometers indicate the corresponding lift. The LX 5000 was at the shortest possible time constant and minimum filtering.

The test was initially performed to see if the Winter with a capacity flask would affect the reading of the LX 5000. That was not the case; the LX 5000 had the same response with and without the Winter connected to the TE line.
The Winter vario reacts almost instantaneously to the pressure change, whereas the LX 5000 needs some time to react (basically given by the set time constant). However, the Winter decays exponentially (and slowly) back to zero and the LX 5000 does eventually catch up. This difference in behavior is easily modeled from the different working principles for the two types of instruments, and similar results have also been observed with more recent LX instruments.

In the lab, flow-based varios like the Winter react faster to sudden changes in air movement than pressure transducer varios. Is it the same in real life?

Jan

On Sat, 30 Dec 2017 15:56:03 -0800, jj9x12345 wrote:

Maybe not in real life, but in the lab (or the workshop) the response of
a Winter vario can be much faster than more modern instruments based on
pressure transducers.

The video at
https://www.youtube.com/watch?v=XmgH...ature=youtu.be shows the
response of a Winter variometer and an LX 5000 connected to the same TE
line. The pressure is quickly reduced by about 1 hPa, and the
variometers indicate the corresponding lift. The LX 5000 was at the
shortest possible time constant and minimum filtering.

The test was initially performed to see if the Winter with a capacity
flask would affect the reading of the LX 5000. That was not the case;
the LX 5000 had the same response with and without the Winter connected
to the TE line.
The Winter vario reacts almost instantaneously to the pressure change,
whereas the LX 5000 needs some time to react (basically given by the set
time constant). However, the Winter decays exponentially (and slowly)
back to zero and the LX 5000 does eventually catch up. This difference
in behavior is easily modeled from the different working principles for
the two types of instruments, and similar results have also been
observed with more recent LX instruments.

In the lab, flow-based varios like the Winter react faster to sudden
changes in air movement than pressure transducer varios. Is it the same
in real life?

"It depends"

IME (slowest-fastest) flow varios I've flown with, this feels right:
PZL, Winter, Sage

IME the PZL is a lot slower than any pressure sensing vario I've used.
I normally fly with old varios (SDI C4 and Borgelt B.40). The C4 has
about the same response rate as other pressure varios of similar age and
the B.40 is very noticeably faster.


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Martin | martin at
Gregorie | gregorie
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