Re: Simplicity (WAS -Re: Mechanical Vario)

At 12:06 08 October 2007, Martin Gregorie wrote:
Paul Hanson wrote:
When
a horizontal gust hits the side of a plane, it creates
positive pressure on one side of the static inputs
(whether fuse or probe mounted), throwing the reading
way out of whack.

I can see that this would make the ASI twitch (and
the altimeter if it
wasn't on cockpit pressure) but I don't see the relevance
to my varios
because:

- my B.40 only has one line that connects to the TE
probe, so the static
isn't affected and you say that a TE probe is relatively
little
affected by gusts.

Relative being a relative term, this is somewhat true.
In comparison it is not AS affected as the static,
but it is indeed affected. There are many plumbing
combos for different types of system, so while something
that works well with one system does not mean it will
work for another. Although in this case, I do believe
you would get better readings from your B-40 with the
Yaw-free TEK probe. Read the stats on the charts for
yourself that I am posting links to in a new post,
that compare a standard TE and a yawing unit under
the same conditions.

- my SDI C4 which has static and pitot as well as TE
connections.
My guess is that it only uses TE for its vario function
and the
static+pitot for airspeed and pressure altitude.

Without actually studying your system your guess is
only that-a guess. Just because the B-40 runs only
on TE does not mean that this one does, although it
may. Rather than guess though, I would do my homework
to figure that out if it were mine before deciding
how to improve anything.

BTW, what the heck is a 'dynamic pressure' probe? Is
it a pitot tube?

Dynamic pressure is what a Pitot tube is measuring,
and what a TE is attempting to create a perfectly matched
inverse of.

Paul Hanson
"Do the usual, unusually well"--Len Niemi


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