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<< Lancair Builders' Mail List >>
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Date: Sun, 30 Dec 2001 19:59:01 +0800
From: "Fred Moreno" <FredMoreno@bigpond.com>
Carl Cadwell posted the following:
"My TAS
speeds at various altitudes are:
9000 209 kts
18000 234 kts
21000 246 kts
25000 264 kts"
.
.
.
Since Carl used GPS data and made three speed runs in three directions
at the same altitude, I assume that the readings he obtained represent
pretty good data.
Fred Moreno
Being a Mathematician(Actuary) by education, I spent some time looking at http://www.reacomp.com/true_airspeed/index.html to verify that the formulae were correct. I initially misinterpreted the concept.
With todays equipment, what I would like to do to measure speed would be to travel in 3 orthogonal(perpendicular) directions using my GPS to maintain course and engine power, verified by the airspeed indicator, to maintain speed. In the article at the above websight, this technique is covered under "Background" and is listed as the David Fox method. This is NOT the method that is used to fill in the numbers on the web sight. Magnetic heading and not true course need to be used in order to use the websight boxes to calculate the true air speed.
My comments are to Carl. Carl, did you use the heading as stated in the websight? If not, we can still use your data with the formulae in the "Background" section to calculate the speeds.
--
Lorn H. 'Feathers' Olsen, DynaComm, Corp.
248-478-4301, lorn@dynacomm.ws
LNC2, O-320, N31161, Y47, SE Michigan
LML website: http://members.olsusa.com/mkaye/maillist.html
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