the past few years. I find that controllers are
now routinely asking for pilot reports on
clouds, but also on air temperature and any
icing. The reports are being fed more efficiently into the system so other pilots are
alerted, and forecasters can improve their
outlooks. The old fear of “gotcha” for pilots
flying unapproved airplanes into icing conditions is gone. I’m not saying there will
never be another violation for flying an
unapproved airplane into real “known”
icing, but the controllers are clearly collecting and disseminating safety information,
not looking to lock us up.
So don’t lock the hangar door just
because there are cold clouds overhead. Just
be sure to have an escape available if those
rare conditions required to actually make
airframe icing are there.
My airplane was due for its biennial
altimeter and transponder checks. Any
airplane that is flown IFR, or any airplane
that has a Mode C transponder, has to have
the altimeter/encoder accuracy, and
transponder performance, checked by a
certified shop every two years.
The altimeter check can be worrisome
with mechanical altimeters and encoders
because with age they can go out of tolerance. The aneroid that drives a mechanical
altimeter can start to leak, or dirt can gum
up the tiny precision gears that move the
mechanism, and hysteresis can alter the
behavior of springs and bellows. Often an
instrument shop can overhaul an out-of-lim-its altimeter, but I have had to junk a couple
over the years.
With new solid-state electronic encoders
and air data computers the lack of accuracy
is usually not an issue. The electronic components tend to work well until they fail
entirely, rather than wandering out of calibration as a mechanical system can.
But a crucial part of the entire test is
checking for leaks in the airplane static air
source system. Even in unpressurized airplanes the air pressure inside the airplane is
usually at least a little different than the air
pressure outside the airplane that the static
What I am most encouraged
by is a new attitude shown
by controllers over the past
few years. I find that controllers
are now routinely asking for
pilot reports on clouds,
but also on air temperature
and any icing.
air system is detecting. A leak in the static
system means both the altimeter and the
airspeed can be inaccurate with no way of
knowing how inaccurate.
When the test equipment was hooked up
to my pitot-static system it wouldn’t hold the
lower air pressure applied to the test equipment. There was a small leak someplace.
This could be a nightmare. The static plumbing connects to two ports on the aft fuselage,
and then runs to a mechanical standby altimeter, two blind altitude encoders, an air data
computer, and the autopilot computer.
There are T-fittings and other couplings in
addition to connections to the electronic
components. And there are various types of
tubing involved, some a rigid walled plastic,
and other rubber-coated flexible lines. The
leak could be anywhere.
But, lucky for me the guys at Mayday
Avionics in Grand Rapids had been through
this hundreds of times, and the first thing
they checked was the alternate static source
valve. I don’t know when the alternate static
had been opened last—maybe during the
annual inspection—but it was not sealing
properly. Opening and then closing the valve
caused it to seat and the leak was fixed. That
was a close call on a lot of shop dollars spent
trying to find a “real” leak. So be careful if
you move the alternate static valve to make
sure it closes tightly.
TOO OLD TO FLY?
The fact that the pilot flying a Cherokee 180
that crashed in Arkansas in November
killing two coaches of the Oklahoma State
women’s basketball team was 82 prompted
me to write a blog about how old is too old to
keep flying. There is no indication that the
pilot’s age had anything to do with the acci-
dent, which involved loss of control in good
VFR conditions, but the news media repeat-
edly called attention to the pilot’s age.
J. Mac McClellan, EAA 747337, has been a pilot for more
than 40 years, holds an ATP certificate, and owns a Beechcraft Baron. To contact Mac, e-mail email@example.com.