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EFIS wind calibration.
My EFIS is set at 121%. Seems OK but how to know? I flew with another Revolt a few months ago and our airspeed did not really match. Did not write them down – loose objects you know. Especially the calculated wind. For a week or so a long time ago on several flights, it read 20mph while sitting still. Yes the sock was hanging down. Today I was up and showed a 2mph tail wind. 180° showed 14mph headwind. Repeatable. Yes, same altitude. Early in the day, light breeze off the Gulf, no thermals yet. How does this highly complex instrument calculate and deliver this info?
I was returning once apon a time and all the aircraft (bigger, stronger, faster and more rigid) were using a runway whose sock was pretty slack but reverse of the runway. My instrument said at 1090 ft it was ~ 15mph. I forget what AWOS said. calm or low number I think. So I loitered about till everyone went away and then called the reciprocal runway (and my reasons).
Ignore instuments and figger it out? Since they can always be wrong, right? Do a low fly-by and check some bird landings..?….while watching the sock of course.
Maybe a bug in the tube that is not dead but lives there and moves about during flight (a year? a family?). In the instrument itself? Can’t blow that out.
I could, long ago, on a sailboat, calculate that stuff with current drift etc. Can’t do it now even if I am just sitting down.
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5 Replies
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Man Jeff, that is a lot…. I’ll try to answer all of your points.
ASI reading 20 when stopped is the ASI menu “zero air speed” This needs to be done from time to time.
The MGLs come factory set at 120% and seem to be accurate at that setting. Without a static port, adjustments are necessary.
You can do a “wind triangle” to verify your airspeed.
Just because the wind on the ground is 0 doesn’t mean there isn’t 15 mPH wind at 1000′
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Regarding head wind and trail wind 180 off. The only time you will have numbers that “add up” is if there is no Xwind creating a crab in both directions. So you need to hunt down your slowest ground speed heading and THEN you can turn 180 and calculate. Mind you if you did that and showed a 12 mph difference your ASI could be off 6 mph. and THEN you can adjust your 121% down to reduce your indicated 6 mph. but it won’t be a 21% adjustment most likely. Also without a static port your ASI will only be truly 100% accurate at one speed. So its possible to throw off your other numbers when calibrating at one particular speed.
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I’ve noticed my ASI has crept up on the ground, but seems to be fairly accurate in the air when contrasted with GS. I am assuming when zeroing that it should be done in no wind, like in a hanger or on a no wind day? LOL. There is no such thing as a no wind day!
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“ASI reading 20 when stopped is the ASI menu “zero air speed””
I have no idea what that means. Easily confused as you know.
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Yes, you will see the option to “zero” your airspeed in the airspeed menu. It quite common to need to do this from time to time. Why? I have no clue. Only know how to fix it.
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