>
>Hi all,
>
>I thought I would take my 914 up to 10,000 feet and run it at 100% power to see
if it would do the mythical 200 mph. Here are the data I recorded.
>
>OAT 16 c
>10,000' @ 29.92
>
>North GPS 129 knots
>South GPS 175 knots
>East GPS 167 knots
>West GPS 140 knots
>
>
>I plugged these numbers into the 4 Axis IAS spread sheet that I got from the
>Europa
club and it tells me that the TAS is 178 knots with a density altitude of
12,310', but..... this is where I get confused. None of my ground speeds are
178 knots, so am I misunderstanding something here, or are the calculations
in the spread sheet incorrect.
>
>
>
Paul,
Try Doug Gray's method, the spreadsheet is far clearer and the
calculation are accurate. And you don't need to steer special headings :
just keep your nose pointed to the same spot on the horizon and read the
track on the GPS.
http://www.kilohotel.com/rv8/rvlinks/doug_gray/TASCALC.ZIP
I run your numbers with it and it yieds a mean TAS of 154 kt , with
variations between 152 and 156 kt according which three runs I consider.
The wind aloft seems to be between 25 and 29 kt for a direction between
325 and 335.
Your measurements seem reasonably consistent. With our Rotax 914 MCR 4S
four seater we averaged 157 kt at FL 120 on a cold day in february. The
size of the two airplanes is quite similar. These are quite respectable
airspeeds.
In my opinion, 200 mph is not a realistic number with an airplane this
size, shape and wing area.
Hope this helps,
Regards,
Gilles Thesee
Grenoble, France
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