Multiple varios

I have yet to fly a glider which has electrical and mechanical variometer that display identical signal all the time. Until then i feel that both mechanical and electrical variometers give more information about the airmass than single one.

On Friday, December 15, 2017 at 10:12:52 AM UTC-5, krasw wrote:
I have yet to fly a glider which has electrical and mechanical variometer that display identical signal all the time. Until then i feel that both mechanical and electrical variometers give more information about the airmass than single one.

Mechanical plays hell with modern (pressure transducer type) electric on same TE circuit. In that event, the mechanical may well be giving the better information.

Results vary depending upon pneumatic impedance of your TE probe and other things...

best,
Evan Ludeman / T8

On Friday, December 15, 2017 at 10:00:02 AM UTC-7, Tango Eight wrote:
On Friday, December 15, 2017 at 10:12:52 AM UTC-5, krasw wrote:
I have yet to fly a glider which has electrical and mechanical variometer that display identical signal all the time. Until then i feel that both mechanical and electrical variometers give more information about the airmass than single one.

Mechanical plays hell with modern (pressure transducer type) electric on same TE circuit. In that event, the mechanical may well be giving the better information.

Results vary depending upon pneumatic impedance of your TE probe and other things...

best,
Evan Ludeman / T8


One mechanical(Sage)on a TE probe and one Westerboer STF with Electronic Compensation. Seems to be an ideal combination. Always check the Sage before I turn.

Mike

On Friday, 15 December 2017 19:00:02 UTC+2, Tango Eight wrote:
On Friday, December 15, 2017 at 10:12:52 AM UTC-5, krasw wrote:
I have yet to fly a glider which has electrical and mechanical variometer that display identical signal all the time. Until then i feel that both mechanical and electrical variometers give more information about the airmass than single one.

Mechanical plays hell with modern (pressure transducer type) electric on same TE circuit. In that event, the mechanical may well be giving the better information.

Results vary depending upon pneumatic impedance of your TE probe and other things...

best,
Evan Ludeman / T8

I had two TE probes in my previous glider, and made a some experiments how much mechanical variometer (Bohli and 0,35l bottle) affect electrical variometer. I flew both variometers with same TE tube or totally isolated TE systems. I could very easily tell different between two different TE probes, but could not see any meaningful difference in electrical vario behaviour if mechanical variometer was connected or not. After flying excellent electrically compensated system last summer I'm thinking that might be way to go in future.

On Saturday, December 16, 2017 at 4:55:21 AM UTC-5, krasw wrote:
On Friday, 15 December 2017 19:00:02 UTC+2, Tango Eight wrote:
On Friday, December 15, 2017 at 10:12:52 AM UTC-5, krasw wrote:
I have yet to fly a glider which has electrical and mechanical variometer that display identical signal all the time. Until then i feel that both mechanical and electrical variometers give more information about the airmass than single one.

Mechanical plays hell with modern (pressure transducer type) electric on same TE circuit. In that event, the mechanical may well be giving the better information.

Results vary depending upon pneumatic impedance of your TE probe and other things...

best,
Evan Ludeman / T8

I had two TE probes in my previous glider, and made a some experiments how much mechanical variometer (Bohli and 0,35l bottle) affect electrical variometer. I flew both variometers with same TE tube or totally isolated TE systems. I could very easily tell different between two different TE probes, but could not see any meaningful difference in electrical vario behaviour if mechanical variometer was connected or not. After flying excellent electrically compensated system last summer I'm thinking that might be way to go in future.

Good for you for testing and paying attention. On my system (I have a 1980s vintage venturi style triple probe, the venturi being at the end of a very restrictive small tube) the capacity / flow of a std Winter vario turns any modern electronic vario into something useless. So my options are either use electronic compensation for the electronic and leave the TE probe for a mechanical, or (current setup) use a B400 as backup (with 4xAA).

"Electronic" compensation can work better than a TE probe. You can't ever get quite to 100% TE compensation with a probe but you can get anything you want with (probe sourced) pitot + static and a good vario. Compensation becomes more critical as TAS and wingspan go up. What works cruising at 80 kts & 6000' won't necessarily cope with 130 (true) and 16,000.

I've been using probe P & S with electronic comp in CNv for a couple of seasons. CNv has the interesting property that one can switch from TE probe to electronic, as well as trim the electronic compensation in flight. Works for me.

Evan Ludeman / T8

On Thursday, December 14, 2017 at 5:00:23 PM UTC-5, John Foster wrote:
Why do so many gliders seem to have multiple varios? Is it that critical to have a back-up for this instrument? Do they often fail and leave you in "
the lurch"?

There is only one essential instrument for VFR and it lies between you ears.
a vario is next, with a vent to cockpit static if the TE gets plugged.

BTW, which Elec varios have an audible sink alarm; the old Cambridge audio was useless in sink as airspeed noise over 60-70 kts covered the LF tone.

In 1970, I built an analogue vario-computer with audio, head up speed to fly reader, TE comp etc..and audio rising tone in lift, and broken tone louder and rising in sink. Just what I needed , but the transducers gave trouble.

John F

"Getting home" may well be possible if your only vario fails. Continuing to race if it fails in a contest is a lot more difficult. It's happened to me at least twice. I don't like single points of failure. The battery, battery selector switch, etc., can be one. The ubiquitous triple probe can be another another.

And, yes, the two varios do sometimes provide different insights.

Chip Bearden

On Fri, 15 Dec 2017 12:24:37 -0800, john firth wrote:

BTW, which Elec varios have an audible sink alarm; the old Cambridge
audio was useless in sink as airspeed noise over 60-70 kts covered the
LF tone.

Borgelt B.40 (and probably other Borgelts as well).

SDI C3 and C4 (he says, naming varios I have a lot of time in the air
with). These have two tomes for climb/sink in climb (TE) mode and another
two for speed up/slow down in cruise (super Netto mode), but my C4
doesn't have a silent band between lift/sink in climb mode, so I turn the
sink option off because I don't need a sink noise to tell me I'm in
searching for lift in somewhat bouyant air at best glide that's just
reducing my sink speed half the dead air value.

This lack of a silent band is a bad feature, of a lot of varios including
some of the LX ones. Ideally it should default to the region between zero
sink and -2kts and its lower limit should be configurable.


--
Martin | martin at
Gregorie | gregorie
| dot org

The ClearNav XC Vario emits a sink tone.

On 12/15/2017 1:24 PM, john firth wrote:
On Thursday, December 14, 2017 at 5:00:23 PM UTC-5, John Foster wrote:
Why do so many gliders seem to have multiple varios? Is it that critical to have a back-up for this instrument? Do they often fail and leave you in "
the lurch"?
There is only one essential instrument for VFR and it lies between you ears.
a vario is next, with a vent to cockpit static if the TE gets plugged.

BTW, which Elec varios have an audible sink alarm; the old Cambridge audio was useless in sink as airspeed noise over 60-70 kts covered the LF tone.

In 1970, I built an analogue vario-computer with audio, head up speed to fly reader, TE comp etc..and audio rising tone in lift, and broken tone louder and rising in sink. Just what I needed , but the transducers gave trouble.

John F

--
Dan, 5J

And thank God you can disable it :-)

On Friday, December 15, 2017 at 5:10:00 PM UTC-8, Dan Marotta wrote:
The ClearNav XC Vario emits a sink tone.

On 12/15/2017 1:24 PM, john firth wrote:
On Thursday, December 14, 2017 at 5:00:23 PM UTC-5, John Foster wrote:
Why do so many gliders seem to have multiple varios? Is it that critical to have a back-up for this instrument? Do they often fail and leave you in "
the lurch"?
There is only one essential instrument for VFR and it lies between you ears.
a vario is next, with a vent to cockpit static if the TE gets plugged.

BTW, which Elec varios have an audible sink alarm; the old Cambridge audio was useless in sink as airspeed noise over 60-70 kts covered the LF tone.

In 1970, I built an analogue vario-computer with audio, head up speed to fly reader, TE comp etc..and audio rising tone in lift, and broken tone louder and rising in sink. Just what I needed , but the transducers gave trouble.

John F

--
Dan, 5J