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Date: Mon, 05 Nov 2012 16:35:08 -0500
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Subject: Re: [LML] Performance Data Walter Engine (and properly calibrated OAT Sensor)
From: Ronald STEVENS <Ronald@sdc.com>
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Oh you are so on the money with this, I had a static port which needed =
an air dam to provide a 'close to accurate' reading. That is why if I am =
suspicious I fly a GPS box, take the real speeds (GS) and have the TAS =
calculated this way. Mine I know is about 8kts off at 17000ft. Which I =
can live with (and yes showing 8 kts faster)

=3D=3D Ronald
=20
On Nov 5, 2012, at 11:39 AM, jeffrey liegner wrote:

> I've been reading everyone's postings about True Airspeed (TAS) and I =
have to ask: are you absolutely certain that your OAT probe is =
accurately reading the outside air temperature? =20
>=20
> Without proper EFIS calibration, or due thermal (engine) contamination =
and also air compressibility, an OAT that reports higher than the real =
temperature will produce an erroneously calculated TAS that is =
remarkably higher than actual. =20
>=20
> This will also throw off the wind speed/direction calculations derived =
from TAS vs Ground Speed (GS) which is presented on your EFIS.  As an =
added footnote, a PIREP using erroneous OAT and report on Winds that is =
fundamentally incorrect is a disservice to other pilots who might rely =
on your report for their decision making.
>=20
> I recently went through some self-study on this subject, and have =
recalibrated my Chelton's "Temperature Recovery" to more accurately read =
the OAT (based on recent NOAA soundings at altitude), and thus to more =
accurately present winds and TAS.  The change in OAT/TAS/Winds is =
notable, and like many men, I discovered my TAS was not as ample as I =
previously thought.
>=20
> This recalibration is only applicable at the same power settings in =
level flight, so OAT in climb does not equal descent.
>=20
> Based on my personal experience, I am now very suspicious when I read =
high TAS, particularly at lower power settings in the flight levels.=20
>=20
> Jeff L
> LIVP
>=20
> --
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