In addition to any set piece calibration test performed as part of the
annual inspection, pilots should be alert for symptoms of pitot static
system problems at any time. An unusual reading may be caused by an
unserviceable instrument, a leakage or a blockage in the system.
Instruments are normally reliable, but linkages can fail, needles may stick
(or fall off!). Major failures will be obvious, but a sticking mechanism
may give a more subtle false reading that may be noticed only by cross
checking cruise airspeed against RPM, or by timing rate of descent against
changes in altitude and the VSI readings.
The possibility of a leakage as a result of the connectors not sealing
properly when fitting the wings on the Europa must always be considered.
The static pressure is not likely to be affected greatly, since the cockpit
and wing root connector pressures are not going to be much different from
that of the static head sensor. However, a leak in the dynamic line will
cause the ASI to under read (including reading 0 if you fail to connect at
all!).
Blockages may be the result of failure to remove the pitot cover/static
plug, ice formation, ingress of water, dirt or insects, or a kinked or
crushed line. These will cause an absent, slow or erratic response to
changing dynamic or static pressure.
I don't want to spread and doom and gloom so as to undermine your confidence
in the instruments. What I am suggesting is that you keep an eye on what's
going on when conditions are good, and investigate any inconsistencies, so
that your instruments will give you accurate information when you need to
rely on them.
Fly safely
Mike
Europa Club Safety Officer
m.j.gregory@cranfield.ac.uk
-----Original Message-----
From: forum-owner@europaclub.org.uk
Subject: Calibration check of pitot static systems
As part of my annual permit renewal, my new UK PFA inspector has asked me to
carry out a check of the pitot static system and instruments. I have located
somewhere to get the ASI and altimeter checked and calibrated as separate
instruments, but what is the best way to check out the plumbing of the pitot
static system? Also, do other people test their pitot static instruments 'in
situ', by adding pressure/vacuum directly to the pitot head? This would
appear to test the whole system - but how would you know whether any errors
lay in the instruments or in the plumbing.
Any ideas on how to deal with this would be most welcome.
David
GBWJH
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