Why is total energy difficult using delta pitot pressure?

On Sunday, July 22, 2012 8:11:02 PM UTC-6, wrote:
The subject says it all

Bill Snead
6W

I would say 90 percent plus of competition pilots use a vacuum total energy probe. From the posts, I would say it is simpler. To use the pitot you must have a good pitot and static system plus a way to reverse the pressure delta (electronic or diaphragms). Any thing else? It also sounds like the pitot input can be made to work. Do you think that the drag from the vacuum probes is very great?

Bill Snead
6W

On 7/25/2012 9:16 PM, wrote:
On Sunday, July 22, 2012 8:11:02 PM UTC-6, wrote:
The subject says it all

Bill Snead 6W

I would say 90 percent plus of competition pilots use a vacuum total
energy probe. From the posts, I would say it is simpler. To use the
pitot you must have a good pitot and static system plus a way to
reverse the pressure delta (electronic or diaphragms). Any thing
else? It also sounds like the pitot input can be made to work. Do
you think that the drag from the vacuum probes is very great?

There is no need to "reverse the pressure delta" in instruments like the
302. The vario uses the pitot/static ports to compute the airspeed, and
from the airspeed, it can calculate the TE compensation. Older analog
varios used various schemes involving diaphragms, calibrated leaks,
etc., but I think those were for netto and other functions, not TE
compensation.

I don't think the drag of the probe is significant.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)