The TE pressure is not necessarily equal to the difference between static
and pitot. It is unlikely to be nor does have to.

The working principle is that the static pressure changes with altitude,
but as the TE pressure is reduced when you go faster and vice versa, the
two components should cancel each other if you push or pull.

If they do not you have climbed / sunk due to rising / falling air.

Jim



At 01:39 18 June 2009, Hellman wrote:
I've been flying gliders for years, but the following question only
occurred to me recently: In mechanically compensated varios, the TE
pressure is supposed to be as much below static as pitot is above
that. That makes sense since "ram air pressure" increases as v^2, as
does the kinetic energy of the ship. But pitot pressure is
proportional to IAS, whereas the kinetic energy of the ship would seem
to need TAS. If I haven't made a mistake (and please correct me if I
have), TE compensation will only be correct at one altitude. At higher
altitudes it will be under compensated, and at lower altitudes over
compensated. Comments please!

Martin