Curious about PZL KWEC-2 TE compensators

I’ve seen these described as an option where you don‘t want to share the TE probe between two varios. However, I can’t find details on them. I’m just curious about how they work (the theory) and how they are plumbed? I know most would use TE probe for one vario and electronic compensation for the other but that’s not an option when using a SN10b. I’m thinking it might be better to use the probe for the 10b alone and the KWEC for the mechanical vario rather than splitting the probe between the two or leaving the mechanical uncompensated.

On Thursday, February 4, 2021 at 6:07:31 AM UTC-8, wrote:
I’ve seen these described as an option where you don‘t want to share the TE probe between two varios. However, I can’t find details on them. I’m just curious about how they work (the theory) and how they are plumbed? I know most would use TE probe for one vario and electronic compensation for the other but that’s not an option when using a SN10b. I’m thinking it might be better to use the probe for the 10b alone and the KWEC for the mechanical vario rather than splitting the probe between the two or leaving the mechanical uncompensated.

I believe the vario cross-talk problem involved large capacity units that used .45 L bottles. I’m running an SN-10 and aa Borgelt 300 that both have small internal capacities on a single total energy probe and I see no cross-talk between these units.
Hope this helps,
JJ

On Thursday, February 4, 2021 at 9:07:31 AM UTC-5, wrote:
I’ve seen these described as an option where you don‘t want to share the TE probe between two varios. However, I can’t find details on them. I’m just curious about how they work (the theory) and how they are plumbed? I know most would use TE probe for one vario and electronic compensation for the other but that’s not an option when using a SN10b. I’m thinking it might be better to use the probe for the 10b alone and the KWEC for the mechanical vario rather than splitting the probe between the two or leaving the mechanical uncompensated.

Most pilots are unlikely to notice the affect of this cross talk.
A practical, though technically imperfect, way of reducing this is to run TE lines from both instruments as far back as possible, normally at least to the rear part of the seat area, and joining with a tee there. This can reduce the cross talk quite a bit.
FWIW
UH

I believe the vario cross-talk problem involved large capacity units that used .45 L bottles. I’m running an SN-10 and aa Borgelt 300 that both have small internal capacities on a single total energy probe and I see no cross-talk between these units.
Hope this helps,
JJ

I’m dealing with a Sage and the .45 bottle. I know about splitting the line further back, I’m just curious about how the KWEC works? I know it has a diaphragm I can’t think it through. If it actually works well, it could be a more elegant solution.

On Thursday, February 4, 2021 at 9:41:50 AM UTC-8, wrote:
I believe the vario cross-talk problem involved large capacity units that used .45 L bottles. I’m running an SN-10 and aa Borgelt 300 that both have small internal capacities on a single total energy probe and I see no cross-talk between these units.
Hope this helps,
JJ
I’m dealing with a Sage and the .45 bottle. I know about splitting the line further back, I’m just curious about how the KWEC works? I know it has a diaphragm I can’t think it through. If it actually works well, it could be a more elegant solution.

I guess we should define vario cross-talk? What I have seen is obvious, dramatic and very confusing! One vario goes up while the other goes down! This is caused by vastly different capacity sizes in the two vario’s. As the ship climbs, air exits both bottles, but the big bottle exits much more air than the little bottle and actually overpowers the small amount of air trying to exit the small bottle.
There were many devices used, back in the day, to solve this problem..........Schumann Box, diaphram, restricters, coiled up tuning, etc. I haven’t seen cross-talk problems in years, probably because we got away from varios that use large capacity bottles like your Schuman vario. I decided 20 years ago to stop using pure mechanical varios like the Winter and Schumann. The new electric varios that use small capacity bottles are fast, but don’t overshoot, accurate, reliable and have audio. The Borgelt has a backup 9v battery, in case you loose ships power............this feature brought me home one day after complete electrical failure. That’s when I discovered I really needed a audio vario to thermal.
JJ

On Thursday, February 4, 2021 at 8:07:31 AM UTC-6, wrote:
I’ve seen these described as an option where you don‘t want to share the TE probe between two varios. However, I can’t find details on them. I’m just curious about how they work (the theory) and how they are plumbed? I know most would use TE probe for one vario and electronic compensation for the other but that’s not an option when using a SN10b. I’m thinking it might be better to use the probe for the 10b alone and the KWEC for the mechanical vario rather than splitting the probe between the two or leaving the mechanical uncompensated.

You can check for the "Wariometr energii całkowitej" paragraph on this website (in Polish - go down slightly beyond the middle of the long page) with an image and explanation:

http://www.plar.pl/szyb/instrum/instrum.htm

A similar explanation found elsewhere on the web and translated by Google says:

"The prototype of KWEC was the Isler compensation box. Schuemann's KWEC (Polish: Kompensator Wariometru Energii Całkowitej - total energy variometer compensator) is a flat, tight box; the two equalizing chambers to which the pressure feeders are connected are separated by a rubber (latex) diaphragm mounted on a spring. As the speed of flight increases, the total pressure increases, and thus the diaphragm bulges, increasing the pressure in the thermos. When the speed drops, the opposite occurs and the pressure in the thermos drops. This way the speed changes in the variometer readings are compensated.
KWEC should be located vertically (diaphragm vertical), and also sideways to the direction of flight (diaphragm parallel to the direction of flight). This eliminates the influence of weight and acceleration.
The disadvantage of this compensation system is the wear of the KWEC rubber diaphragm, which should be replaced after approx. 10,000 cycles. Accurate compensation is difficult to obtain. Additionally, one KWEC must be used for each variometer."

On Thu, 04 Feb 2021 12:30:04 -0800, John Sinclair wrote:

The Borgelt has a backup 9v battery, in case you loose ships
power............this feature brought me home one day after complete
electrical failure. That’s when I discovered I really needed a audio
vario to thermal.
JJ

I use an SDI C4 as my main vario and a Borgelt B.40 for backup. Both are
pressure sensing electric vario, so don't use capacity falsks and don't
interfere with each other despite the TE line only forking about 1 foot
(30cm) away from the varios.

JJ is right about the Borgelt varios: I'd hate to be without my B.40. It
will run for 8-12 hours of a PP3 9V battery, though both varios are
normally powered off a 12v SLA - SDI C4 doesn't have a back up battery,
so my backup 'get home' system is the B.40 and my Medion PDA, which runs
LK8000 and has an internal battery.

Bottom line: if you need a second vario and somebody offers you a B.40,
grab it with both hands. It also very good for ridge running.


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

On Thu, 04 Feb 2021 13:12:03 -0800, Tom BravoMike wrote:

On Thursday, February 4, 2021 at 8:07:31 AM UTC-6,
wrote:
I’ve seen these described as an option where you don‘t want to share
the TE probe between two varios. However, I can’t find details on them.
I’m just curious about how they work (the theory) and how they are
plumbed? I know most would use TE probe for one vario and electronic
compensation for the other but that’s not an option when using a SN10b.
I’m thinking it might be better to use the probe for the 10b alone and
the KWEC for the mechanical vario rather than splitting the probe
between the two or leaving the mechanical uncompensated.

You can check for the "Wariometr energii całkowitej" paragraph on this
website (in Polish - go down slightly beyond the middle of the long
page) with an image and explanation:

http://www.plar.pl/szyb/instrum/instrum.htm

A similar explanation found elsewhere on the web and translated by
Google says:

"The prototype of KWEC was the Isler compensation box. Schuemann's KWEC
(Polish: Kompensator Wariometru Energii Całkowitej - total energy
variometer compensator) is a flat, tight box; the two equalizing
chambers to which the pressure feeders are connected are separated by a
rubber (latex) diaphragm mounted on a spring. As the speed of flight
increases, the total pressure increases, and thus the diaphragm bulges,
increasing the pressure in the thermos. When the speed drops, the
opposite occurs and the pressure in the thermos drops. This way the
speed changes in the variometer readings are compensated.
KWEC should be located vertically (diaphragm vertical), and also
sideways to the direction of flight (diaphragm parallel to the direction
of flight). This eliminates the influence of weight and acceleration.
The disadvantage of this compensation system is the wear of the KWEC
rubber diaphragm, which should be replaced after approx. 10,000 cycles.
Accurate compensation is difficult to obtain. Additionally, one KWEC
must be used for each variometer."

I may well be wrong, but to me the KWEC sounds more like a TE probe
replacement rather than a device for preventing a flow-based vario from
interfering with a pressure-sensing one.



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

That is my understanding too. Cross-talk is the problem being avoided. One vario is compensated with the TE probe and the other independently compensated with the KWEC. Thanks for the link! There is some good info there including the for the plumbing. If it works it is actually quite simple and ingenious.

On Thursday, February 4, 2021 at 8:19:02 PM UTC-5, wrote:
That is my understanding too. Cross-talk is the problem being avoided. One vario is compensated with the TE probe and the other independently compensated with the KWEC. Thanks for the link! There is some good info there including the for the plumbing. If it works it is actually quite simple and ingenious.

I had the KWEC-2 in my ASW-20 for a while for same reason. It's better than nothing, but pretty underwhelming. If you stay under 70 knots and 6000', it works sort of okay. The compensation goes away pretty fast with altitude.

T8