Flight Training - May 2020 - 14

PREFLIGHT FLIGHT LESSON

BY DAVID AGRANOVICH

TROUBLESHOOTING ON TOP
PARTIAL ELECTRICAL FAILURE IN IMC

WHAT HAPPENED

"It was essentially
a partial-panel
situation, but I
hadn't lost
anything vital."

was primarily concerned with the circuit
causing a fire or another electrical issue.
A few minutes later, I broke out above a
solid cloud deck that was breaking up to the
south. I ran the autopilot emergency procedure checklist and pulled the breakers for
the Bus 2 equipment I could live without. At
this point, I could shoot a familiar approach
back into my home airport, where the cloud
bases were well above the minimums and
which would minimize my time in the air, or
I could proceed in visual conditions above
the clouds to an area where a VFR descent
and landing would be possible at another
airport. The latter option would have taken
me several miles over open water.
I requested vectors to final for the
ELECTRICAL FIRES
I HAD JUST EARNED MY INSTRUMENT RATING, AND
approach back to my home airport, and the
decided to take my first solo IFR flight, since the
approach and landing were uneventful. On
weather was perfect to fly through clouds below the
the ground, I found the Bus 2 rocker switch
Diagnosing a fire when
freezing layer for some time in actual instrument conhad welded itself in the open position.
ditions. I was flying a new-to-me club Cessna 172S with you don't see flames
The experience taught or reinforced
a Garmin G1000 and a KAP140 autopilot. I'd had equipseveral lessons.
ment failures before-everything from a vacuum failure Avionics failures and
ATC is your best ally, especially flying
other abnormal behavior
to a cracked cylinder-but never in the clouds.
single-pilot IFR. In extremely busy airspace,
of electrical components
may be signs of a hidden
I was climbing in clouds through 3,000 feet msl to
the approach controller still did everything
electrical fire. The AOPA
my en route altitude of 7,000 feet, and knew from area
he could to help, including an amended
Air Safety Institute
pilot reports that the cloud tops were around 6,000
route and approach clearance on the fly.
recommends shutting
feet. With the autopilot on, I was tracking a GPS course down all unnecessary
Don't panic. I wasn't in immediate
electrical equipment if
direct to the destination's initial approach fix.
danger, I had my primary instrumentation,
a fire is suspected, and
The first indication of a problem was that my
keeping a small Halon
and all the instruments and navigational
fire extinguisher handy in equipment I needed. It was an entirely
number-two com radio went intermittent while I was
the cockpit just in case.
trying to pick up the automatic terminal information
manageable situation.
airsafetyinstitute.
service (ATIS) for my destination. While troubleshoot- org/safetyadvisors/
Know your systems. Knowing what
ing the radio failure and checking the electrical system, emergencyprocedures systems mapped to which part of the elecI heard a terrible noise behind me-which I later
trical system made it easier to determine
realized was likely the autopilot servo. I switched off
what I'd lose by pulling a breaker.
the autopilot, but the damage seemed done.
If you're concerned, declare an emerThe autopilot circuit breaker had not popped, but
gency. This lets people on the ground
everything on Bus 2 went intermittent: no multifuncknow that things could get worse and will
tion display, number two com, nav radios, or autopilot.
ensure that emergency services are availI reported the malfunction to ATC and requested an
able if you do end up needing them.
altitude/vector out of the clouds. It was essentially a
partial-panel situation, but I hadn't lost anything vital,
David Agranovich is an instrument-rated private
and my battery/alternator indications were normal. I
pilot living in San Francisco.

SIGNS OF TROUBLE

LEFT: SARAH HANSON; ABOVE: STEVE KARP

14 FLIGHT TRAINING MAY 2020

http://airsafetyinstitute.org/safetyadvisors/emergencyprocedures

Flight Training - May 2020

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