Tuesday, May 11, 2004

Vario's 101

I originally wrote this for Andrew, since we are going to do some more thermal practice tomorrow, but when I was about to send it then I figured you guys might get some use out of it.

So, you went and bought a vario - now how do you use it? Well, first lets go over what it does and talk about setting it up to be useful. A vario is short for 'variometer', which means it measures variations in pressure.

Most varios actually contain two different varios - an analog and a digital. Other than the obvious altimeter function, the main purpose is to tell you if you are in rising or sinking air. It does this by using a temperature calibrating pressure sensor.

The analog vario is usually a visual meter, either a speed-gauge looking thing or a volume meter looking thing. I'm being very technical here. :)

The digital vario is a digital display that shows the rate of climb/descent in number format, either in feet per minute or meters per second. I use feet per minute mode since I'm allergic to the metric system.

It’s important to note the difference here between the two. The analog is an up to the minute reading - if it says 200 up, then you are going 200 up. The digital vario on the other hand is an averaging vario. It takes a running sample and updates the digital display with the average climb/descent at a given interval. Most varios have a standard setting of 5-10 seconds. I like to set mine to a minimum of 15 seconds and usually keep it at 30 seconds. I keep mine high since if I'm struggling to find a thermal, having it set to a long interval lets me know if I'm in a general area of lift or sink. I may not be in a thermal, but if the air is buoyant in the area, I'll know it with the higher interval and I may hang out in the general area a little longer. For a beginner, I'd say keep the default from the factory.

Now lets talk about the audio output of a vario – yup, they make noise too. With the motor at idle, you can usually hear the vario, even at the lowest sound setting (they have three sound levels, loud, louder, and silent). It beeps when you are going up, buzzes when you are going up -the faster you go (up/down) the faster it beeps/buzzes.

Not much too it, but you can set the threshold for when the beeping/buzzing starts. Why is this important - well, most varios were first made for hang gliders and the default buzz/beep is set to around 100 feet per minute. Your average paraglider has a hands off sink rate of around 220 fpm in calm air. If you go with the default, you gotta listen to lots of buzzing. This is annoying, frustrating, and can lead to unnecessary stress when trying to avoid sinking out.

I have my climb beep set to start at 200 fpm and the buzz to start at -400 fpm - I'd rather not hear the buzz, but if I hit moderate sink I'd like to know about it (not like the glider won't have already given me the feedback - its more of a motivator, I hate the buzz, so I have to get out of the sink to get it to stop). BTW, the sound is linked to the analog (instant) vario, not the digital one.

So, now you are flying. You have the vario strapped to your left leg. You climb up to 1200 ft and idle the motor and start heading to the edge of the field that should be going off. You get halfway across the field and hit some light sink and decide to turn. You crank an hard right hand turn and mid way into it your vario starts to beep - Thermal!! ..... NOT! You just cranked such a hard turn that you swung out, and up, to the left and that set the vario off. Its something to watch, especially if you make hard banking turns (yet another reason to keep your turns flat, as if the increased sink rate of a high bank turn wasn’t enough of a motivator).

I won't get into thermal technique, but don't fixate on the vario - just fly and listen for the beep and when you snag one, use it to stay in it and find the core. If you loose it and aren't getting any lift (or zero sink) then just pick a direction and head that way. Go straight until you find anther one. And remember, zero sink is just as good as lift - going up us good, but as long as you aren't going down, then that’s good too. Hang out in areas of zero sink because they might lead you to boomer.

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