Actually those are not bad calculation results. I have seen similar even in a cirrus. (about 7-10kts off). So I do not think it is worth going through the hassle of changing the location.

I would start doing work when it would have been more then 15kts off. You will see that the TAS calculation also differs at high or low speed. (do the same at the same level at 110kts IAS and once at 170IAS) and if you did you will see that the spread also is different, so when it really matters a lot (traffic pattern) it will be close to what it should be (that were my observations when I did the calcs)

== Ronald
 

On Aug 19, 2012, at 9:36 AM, jeffrey liegner wrote:

> Recall my question (same subject) about the accuracy of OAT, and its efect on TAS and Winds.  SInce I rendere pireps including winds and OAT, the accuracy of this report is now in question.  Many have suggested reloacting the OAT to another place, different from the Lancair recommendation along the fuselage.  This is not an easy thing, putting the probe out on the wing, wiring coming into and through the wing root, into the pressure vessel (different from the current OAT location).
>
> I performed the flight TAS calculation recommended by several.  Whether three measurements with headings 120 degrees apart, or three orthogonal headings, the results are the same.
>
>
> The Chelton presents a TAS 216 and the calculator renders TAS 205 based on the n flight measurement.
>
> I wonder if I can change the compressibility quotient used by Chelton to adjust the OAT reading.
>
> Suggestions?
>
> Jeff L
> N334P
>
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