WTB E-Vario

On Tuesday, September 29, 2015 at 12:15:04 AM UTC-4, wrote:
I used an Lnav many moons ago (1990) and although a good unit at the time a little antiquated.

I'll echo JJ's comments about the LNAV. I bought mine in 1992 and it's worked great ever since, for most of that time coupled with an "antique" Compaq 1550 running Glide Navigator II. I'm currently exploring a flight computer upgrade using open source software (e.g, TopHat) and a cheap tablet. But based on input from several pilots whose opinions I trust, including several national champions, I've been reassured that any improvement in the new varios vis-a-vis the LNAV is modest, at best, and doesn't justify my investing the required price. I'll revisit if it looks like I need more of a data stream than can be provided by my current hardware (or if my fellow pilots are lying to me in order to hobble my performance!) but in the meantime, I'll continue to rely on the LNAV.

Chip Bearden
ASW 24 "JB"
U.S.A.

It's very easy to install a top quality vario and drag it down to below LNav performance. Sharing a TE source with a mechanical vario (think of it as a big leak) is the most common problem I see. How much havoc this causes depends upon things we don't have good ways to measure (e.g. the impedance of the TE system).

Evan Ludeman (ClearNav guy)

If you split the total energy line, as far aft as possible, the cross-talk between varios is all but eliminated. I am running an SN-10 and B300 that share the TE signal that is split under the seat with 2 lines going forward.my varios are side by side and I see no cross-talking going on.
JJ

On Tuesday, September 29, 2015 at 9:26:58 AM UTC-4, JJ Sinclair wrote:
If you split the total energy line, as far aft as possible, the cross-talk between varios is all but eliminated. I am running an SN-10 and B300 that share the TE signal that is split under the seat with 2 lines going forward.my varios are side by side and I see no cross-talking going on.
JJ

That system ought to be fine. The SN-10 is a flow type vario (iirc), but probably small flask volume and flow compared to a Winter, etc. The B300 is a pressure transducer vario... but if it's anything like my B400, it's a pretty slow e-vario, so no real issue expected.

best,
Evan

I suspect you're right, T8. Would that also apply to the LNAV itself? That might make me finally address the issue of sharing a triple probe TE with my Winter backup vario, which has been the case since the glider was new in 1992. The biggest sin, I imagine, is using a "T" connection immediately behind the instrument panel rather than a "Y" farther back in the fuselage. Question: would you expect both varios to benefit from this, or just my LNAV?

Chip Bearden
ASW 24 "JB"
U.S.A.

On Tuesday, September 29, 2015 at 9:30:30 AM UTC-4, wrote:
I suspect you're right, T8. Would that also apply to the LNAV itself? That might make me finally address the issue of sharing a triple probe TE with my Winter backup vario, which has been the case since the glider was new in 1992. The biggest sin, I imagine, is using a "T" connection immediately behind the instrument panel rather than a "Y" farther back in the fuselage. Question: would you expect both varios to benefit from this, or just my LNAV?

Chip Bearden
ASW 24 "JB"
U.S.A.

I haven't played with an LNav in a long time. I think that's a flask/flow type instrument and those always seemed more tolerant of sharing TE with a mechanical.

We really started seeing problems when guys tee'd their new 302s in line with Winter & Sage varios. Didn't affect the mechanical, but the 302 acted lobotomized.

Whether splitting the TE line helps probably depends on the impedance of your probe. I've got one of those oldie but goodie venturi type triple probes and the venturi is mounted at the end of a rather small capillary. The impedance is high and I gave up trying to get a mechanical to play nice with a 302... solution was replace Winter with B400 for backup (pressure transducer instruments can share pneumatic sources, no issues here).

The other thing that can work is running your fancy primary vario off pitot + static with "electronic" compensation and leave the probe for your mechanical. In this case, the pitot and static need to be *really* good (fin mount triple probe) and not shared with mechanical instruments.

best,

Evan Ludeman

The other thing that can work is running your fancy primary vario off pitot + static with "electronic" compensation and leave the probe for your mechanical. In this case, the pitot and static need to be *really* good (fin mount triple probe) and not shared with mechanical instruments.

Yes, the LNAV is a flask/flow vario. I do notice what could be some minor transient cross talk between it and the Winter but I'm used to it.

In my previous glider, I had two identical older Cambridge varios (IIRC, something called a Mark II, but pre MNAV) on completely separate pneumatic (and battery) systems: one on a Schuemann TE compensator connected to pitot and fuselage statics and the other on a venturi with a homemade netto capillary connected to forward fuselage statics. After flying around with loops of instrument tubing in my lap one day changing the length of tubing on the Schuemann and the number of hypodermic needle restrictors on the homemade netto, they both read nearly identically during pull ups and pushovers. I had a Cambridge audio for which Raouf Ismail graciously made up a special switch that I could toggle from one vario to the other if I needed. I loved that system!

I confess that I did look at other varios in the past with the objective of getting electronic TE that would provide that 100% independence I had in my previous panel. I have lost primary varios several times over the years and it's an unsettling feeling.

Chip Bearden
ASW 24 "JB"
U.S.A.

On Tuesday, September 29, 2015 at 9:30:16 AM UTC-5, Tango Eight wrote:

The other thing that can work is running your fancy primary vario off pitot + static with "electronic" compensation and leave the probe for your mechanical. In this case, the pitot and static need to be *really* good (fin mount triple probe) and not shared with mechanical instruments.

That is my approach - my SN10 gets fed by a nice Ilec TE probe, and my other vario is the really nice electronic TE Westerboer 1020, which works just fine using the aircraft pitot and vario statics.

No concerns with TE probe leaks, cross talk, etc...

Mechanical varios are so last century....

Kirk
66

It's been a while since I did the research. What are the logical choices for a reliable vario (to use as a backup) with electronic TE? Include used.

Chip Bearden
ASW 24 "JB"
U.S.A.

On Wednesday, September 30, 2015 at 3:42:25 PM UTC-4, wrote:
It's been a while since I did the research. What are the logical choices for a reliable vario (to use as a backup) with electronic TE? Include used.

Chip Bearden
ASW 24 "JB"
U.S.A.

Used Cambridge 302 with GPS date bug. Good, electronic TE capable, cheap.

best,
Evan

On Wednesday, September 30, 2015 at 2:42:25 PM UTC-5, wrote:
It's been a while since I did the research. What are the logical choices for a reliable vario (to use as a backup) with electronic TE? Include used.

Chip, the Westerboer VW1020 can be setup to use either a TE probe or electronic compensation, via Pitot and Static. I've used several Westerboers and really like them.

http://wingsandwheels.com/westerboer-vw1020.html

Kirk
66