airspeed indicator problem after TT2 transponder install

At 23:38 04 March 2011, Darryl Ramm wrote:
Which manufacturer intends the ships's ASI to ever be connected to (or
switchable) to a tail mounted pitot and/or static? The ASI should only
be connected to the nose pitot and fuselage main static. A vario/
flight computer (like my C302) might be switchable between both (as it
is in my motorglider).

Darryl


Schempp Hirth.
My Discus only has fin pitot.

Presumably this is so that the ASI still works when the nose hook is used
for aerotow.
(Not sure why knowing the speed on tow is important?)

Kevin

On Mar 5, 3:01*am, BruceGreeff wrote:
AHEM - my T59D has a pitot on the tail fin - sharing space with the TE
probe...

That was way back in 1971 and is actually not that uncommon an arrangement.

On Mar 5, 4:33*am, Kevin Neave wrote:
At 23:38 04 March 2011, Darryl Ramm wrote:

Which manufacturer intends the ships's ASI to ever be connected to (or
switchable) to a tail mounted pitot and/or static? The ASI should only
be connected to the nose pitot and fuselage main static. A vario/
flight computer (like my C302) might be switchable between both (as it
is in my motorglider).

Darryl

Schempp Hirth.
My Discus only has fin pitot.

Presumably this is so that the ASI still works when the nose hook is used
for aerotow.
(Not sure why knowing the speed on tow is important?)

Kevin


I was talking about motorgliders. AFAIK Schempp-Hirth motorgliders
have nose mounted pitots for the ASI and do not switch the ASI pitot
source to a tail pitot.

I've seen the ASI on some gliders like my old club's DG-1000S bouncing
around a fair bit as we aerotowed at times with a wiffle ball on the
tow rope (to protect the rope from abrasion damage). That tow operator
liked to use a round wiffle ball followed by a half cut wiffle ball
that could get a pretty good cup over the nose of the glider and the
actual impact on the ASI would depend on how exactly that half cut
ball sat on the nose. But since you are following a towplane this is
less of a potential problem than would be using an ASI accidentally
switched to a tail mounted pitot when self launching a motorglider
(not that motorglider manufactures actally would intend anybody to do
that, sigh.).

Darryl

On Mar 4, 3:47*pm, Don Johnstone wrote:

Man who teach me to fly he say, "Never ever blow in pitot, altimeters are
not designed to deal with being blown"

Are you sure that's what he said? How would blowing into a pitot have
any impact on the altimeter?

Applying pressure to pitot tubes is a standard method of testing
airspeed systems. You can buy quite expensive test equipment to do
just that. The same test equipment will also vary the static port
pressures although that's typically a suction.

For comparison testing of airspeed indicators, such as a mechanical
ASI and the Cambridge 302, one can either gently blow on the pitot and
gently suck on the static while observing the instrument readings. If
the mechanical ASI does not go off scale no harm can be done.

Andy