What's a normal response delay for a paragliding vario?

Question

I'm a paragliding pilot with P4 licence and I've purchased a 2nd-hand FLYMASTER B1NAV flight instrument for XC flights – mainly for logging the flights (route, distance, max. speed etc). It is an Altimeter-Variometer-GPS combo. As you know, these devices warn the pilot with beeps during climbing and sinking.

I'm using the device for a couple of months but I recently noticed an interesting thing: When I enter the thermal I first feel the climb with my harness and risers. But the device starts to beep with a delay of 1-2 seconds.

Is this normal?

I know it's an old and discontinued product. I've looked into its manual, but couldn't find any info about the delay. I don't want to rate this device as "broken", but I cannot be sure.

Answer 1

That is probably normal. I notice a similar delay when flying with my Brauniger IQ Comp vario (lately mainly in sailplanes.) Minimizing the delay is why the latest varios incorporate accelerometers as well as barometric pressure sensors. Sounds like you've already checked the manual to see if there is some way you can decrease the interval of averaging, upon which the primary visual display and audio tone are based. That adjustment is definitely possible with some variometers produced for hang gliding / paragliding use, but not with all.

Another way to get a quicker response time is to buy a vario that is even older. For example, check out the "Litek Hummingbird".

Answer 2

Yes, that is perfectly normal. It's physically unavoidable to feel the lifting force, that sets a rise into motion, before that rise can be measured. The only faster way I could think of were to measure rope tension instead of altitude.

As for the duration of the delay: The manufacturer knows that there is some measurement noise (fluctuation), and needs to smooth it out. If they determined that the measurement might fluctuate within a 10 cm range in any given second, they will not alert you unless you have climbed 11 cm.