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  #1  
Old 06-22-2016, 10:21 PM
mavmitchell mavmitchell is offline
 
Join Date: Jul 2013
Location: Perth
Posts: 27
Default G3X Air Speed calibration tool

Hi All. I just did a quick and dirty tool to plot TAS and Ground speed to visualise any ASI errors. Takes G3X Logs. Just add Airspeed correction to centre the AS Diff circle. It does need enough data in opposite directions..




Find it Here
Cheers.

Last edited by mavmitchell : 06-23-2016 at 04:01 AM.
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  #2  
Old 06-23-2016, 06:17 AM
Kevin Horton's Avatar
Kevin Horton Kevin Horton is offline
 
Join Date: Jan 2005
Location: Ottawa, Canada
Posts: 2,357
Default

Does it account for the effect of crosswind? I.e., if you have a wind from the west, the average GS from two runs on 090 and 270 degrees will be different from the average GS from two runs on 000 and 180 degrees, assuming the same TAS on all legs.
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  #3  
Old 06-23-2016, 06:38 AM
mavmitchell mavmitchell is offline
 
Join Date: Jul 2013
Location: Perth
Posts: 27
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Hi Kevin,

This is a graph of the TAS without alteration. The idea is to adjust the "Air Speed Correction" to centre the "AS Diff"(red) on the rose. With it centred, the "Air Speed Correction" is the error in the pitot/static system. This actually means the "AS Diff" in the crosswind is ignored because it is always at or near zero.

Cheers..
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  #4  
Old 06-23-2016, 07:31 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 5,516
Default What difference is acceptable?

I am a little confused as to the scale for reading the airspeed difference on this graph. Will it clearly show 2 knots difference?

And - what difference is considered acceptable?
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“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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  #5  
Old 06-23-2016, 07:53 AM
mavmitchell mavmitchell is offline
 
Join Date: Jul 2013
Location: Perth
Posts: 27
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Hi Bill,

I have looked at a number of logs. This is just a visualisation, but it seems easy to see errors as low as 1kt.

What's acceptable is up to you, but I would be happy with anything less than 2Kts.

Cheers..
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  #6  
Old 07-02-2016, 12:47 PM
chasers03 chasers03 is offline
 
Join Date: Aug 2015
Location: Seneca, SC
Posts: 23
Default G3X True Air Speed correction possible?

I have calibrated my WOT True Airspeed at 116k however the G3X shows 113k. Is there a way to put a correction factor into the Garmin resulting in the TAS displaying 3k higher?

Thanks from Steve Chase
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