AA Butterfly versus CNv LCD wind calculation

Wow, it hasn't even crossed my mind that someone would omit mechanical vario. That is the basis of glider instrumentation. Walking trough grid of last wgc most gliders had mechanical vario at prominent location in panel, I did not remember seeing one without.

I have two TE probes in my glider and have tried both mechanical and electric varios with same and separate probes. I did not find any differences plumbing them to same TE source.

On Monday, September 26, 2016 at 1:19:46 PM UTC-4, Dan Marotta wrote:
On 9/26/2016 10:15 AM, Tango Eight wrote:
snip
Mechanical varios don't play well with modern pressure transducer type varios and should not share TE sources with them.

Evan Ludeman / T8

I have a 57 mm Winter mechanical and a CNvXC connected to the triple
probe in my Stemme. The needles on each track perfectly with each
other.

Which illustrates what goes wrong :-).

The effect of the mechanical vario is to slow the whole system down to its own speed.

If you are using the triple probe pitot and static for CNv's pitot and static inputs, and the static source is not shared with any mechanical instrument (pitot source may be shared with an ASI since the pitot aneroid volume is small), try setting CNv to "no probe" and see if you don't like the response of the instrument better. I suggest setting the audio & pointer time constants to 0.5 sec.

best,
Evan for CNi

On Monday, September 26, 2016 at 9:41:21 AM UTC-6, jfitch wrote:
On Monday, September 26, 2016 at 8:35:58 AM UTC-7, krasw wrote:
On Monday, 26 September 2016 17:24:02 UTC+3, Richard wrote:
On Sunday, September 25, 2016 at 11:15:12 PM UTC-7, krasw wrote:
On Monday, 26 September 2016 04:25:15 UTC+3, Sean wrote:
LXNav S10 backup this spring for my new panel. I do not think the butterfly is worth the price...

SMF
7T

What are you backing up with S10? Don't you have mechanical vario?

No need for a mechanical backup the S10 has an internal backup battery for 3 hrs of use.

Richard
www.craggyaero.com

Never heard of anyone not having a mechanical vario in glider.

I don't.

I also do not have a mechanical vario...No need (at least for me) at all....In fact I am somewhat amazed folks are still buying them. Perhaps some clubs still buy them for simplicity or for some other reason, but I haven't had one in many years...

On Monday, September 26, 2016 at 1:05:36 PM UTC-4, wrote:

Mechanical varios don't play well with modern pressure transducer type varios and should not share TE sources with them.

Evan Ludeman / T8

A practice many seem to ignore. Do you think there is any advantage to using a fin mounted Prandtl tube versus fuselage pitot/static ports? Do you prefer mechanical or electronic TE? How do you "plumb" your CNvXC and B400?

CNv works great on electronic compensation *provided* the pitot/static system is essentially perfect. The only practical, reliable way to get that is with a triple probe set up on the fin. Don't share the static with mechanical instruments.

I have a triple probe set up plus fuselage static ports.

I plumb all three triple probe sources to CNv, the TE also goes to B400. ASI uses triple probe pitot and fuselage static. CNv works well on the probe (an old venturi style probe) but even better on the pitot/static.

best,
Evan

I do not have a mechanical vario. I have a computer with vario, a Butterfly and I have a LX V3 with battery backup, which I think is much better than a mechanical vario. I usually just leave the V3 off, but if I lose my main bus, I still have an electric vario with audio good for 8 hours of flight time. The V3 can be run off main power or battery backup. This V3 vario has it's own speaker so it is a compact install. I believe a few other manufacturers off the same type of functionality.



On Monday, September 26, 2016 at 8:35:58 AM UTC-7, krasw wrote:

Never heard of anyone not having a mechanical vario in glider.

Thanks Evan, I was gonna try that. I already have the TCs set at 0.5
sec. I'll report back if I see any difference.

Dan

On 9/26/2016 12:14 PM, Tango Eight wrote:
On Monday, September 26, 2016 at 1:19:46 PM UTC-4, Dan Marotta wrote:
On 9/26/2016 10:15 AM, Tango Eight wrote:
snip
Mechanical varios don't play well with modern pressure transducer type varios and should not share TE sources with them.

Evan Ludeman / T8
I have a 57 mm Winter mechanical and a CNvXC connected to the triple
probe in my Stemme. The needles on each track perfectly with each
other.
Which illustrates what goes wrong :-).

The effect of the mechanical vario is to slow the whole system down to its own speed.

If you are using the triple probe pitot and static for CNv's pitot and static inputs, and the static source is not shared with any mechanical instrument (pitot source may be shared with an ASI since the pitot aneroid volume is small), try setting CNv to "no probe" and see if you don't like the response of the instrument better. I suggest setting the audio & pointer time constants to 0.5 sec.

best,
Evan for CNi



--
Dan, 5J

The triple probe on the Stemme extends to about 3 feet in front of the
nose. That should be in pretty much undisturbed air.

On 9/26/2016 12:20 PM, Tango Eight wrote:
On Monday, September 26, 2016 at 1:05:36 PM UTC-4, wrote:
Mechanical varios don't play well with modern pressure transducer type varios and should not share TE sources with them.

Evan Ludeman / T8
A practice many seem to ignore. Do you think there is any advantage to using a fin mounted Prandtl tube versus fuselage pitot/static ports? Do you prefer mechanical or electronic TE? How do you "plumb" your CNvXC and B400?
CNv works great on electronic compensation *provided* the pitot/static system is essentially perfect. The only practical, reliable way to get that is with a triple probe set up on the fin. Don't share the static with mechanical instruments.

I have a triple probe set up plus fuselage static ports.

I plumb all three triple probe sources to CNv, the TE also goes to B400. ASI uses triple probe pitot and fuselage static. CNv works well on the probe (an old venturi style probe) but even better on the pitot/static.

best,
Evan

--
Dan, 5J

The mechanical vario and compass may have disappeared from your consciousness, but I bet they are still on the required equipment list from your glider's manufacturer. Something to remember at your next annual inspection. Just sayin'

In the ASG-29 a vario is minimum equipment for France, but does not specify electric or mechanical. USA required ASI, ALT, Compass 9which I am not sure why i need as I have two gyro compasses.


On Monday, September 26, 2016 at 6:17:06 PM UTC-7, wrote:
The mechanical vario and compass may have disappeared from your consciousness, but I bet they are still on the required equipment list from your glider's manufacturer. Something to remember at your next annual inspection. Just sayin'

On Monday, September 26, 2016 at 8:17:06 PM UTC-5, wrote:
The mechanical vario and compass may have disappeared from your consciousness, but I bet they are still on the required equipment list from your glider's manufacturer. Something to remember at your next annual inspection. Just sayin'

Compass, yes, unfortunately (so I have a small PZL hidden behind my Oudie). Vario - not at all.

I feel safer with an all-glass cockpit (with suitable power supplies) than with any mechanical instrument. ASIs, altimeters, varios - the mechanical ones have all failed much more frequently than any of my electronic instruments.

And if all the blue smoke escapes, then it's back to basic airmanship. Look out the window, fly pitch attitude, feel the air... BTDT (due to mechanical instrument failures).

YMMV, of course ;^) A glass cockpit in a 2-33 would be a bit weird!

Kirk
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