Flight Training - December 2014 - 26

FLIGHT LESSON

By Harvey Greenberg
FLIGHT LESSON oﬀers the
opportunity for pilots to learn
from the experiences of others.

ICE ON MY MIND

CARB HEAT SAVED MY BACON

D

uring my 35-year ﬂying career, I have experienced my share
of carburetor icing, but nothing remotely like what occurred
on both legs of a cross-country between Penn Yan, New
York, and Lebanon, New Hampshire, in April/May 2014.
When I encountered carburetor icing previously, it presented as the
classic slow degradation of performance scenario. Application of carb
heat made the engine run rough for a few seconds before clearing, at
which point I could resume normal operations or, in some cases, leave
carb heat on if the problem was persistent. As additional context, most
of my serious cross-country time has been in fuel-injected airplanes, in
either a Piper Arrow or, more recently, a Cirrus SR20.

26 /

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and sudden decrease of power. I immediately applied carb heat, adjusted power
and mixture, and the engine came back
to life. The remainder of the ﬂight was
uneventful, but I was careful to apply carb
heat prior to further power reductions.
Ice was on my mind for the return
ﬂight, but this time it was airframe icing.
Having ﬁled the return leg for a late-afternoon departure at 8,000 feet, I learned
from my preﬂight brieﬁng that there was
an Airmet Zulu for the entire leg with
multiple cloud layers through 13,000. No
pilot reports were available. The forecast
temperatures aloft were minus 4 degrees
C at 8,000 and minus 1 degree at 6,000,
with ceilings on the surface reasonably
high. My primary plan was to try 8,000
ﬁrst, use 6,000 as a Plan B, and be ready to
execute the nearest instrument approach

SARAH HANSON

This trip was in our ﬂying club's
Piper Cherokee (PA-28)-my ﬁrst trip
in a carburetor-equipped airplane since
2010. The outbound leg featured dismal
weather at departure with clearing toward
New Hampshire, and after being in and
out of clouds and light rain at 9,000, I was
enjoying visual conditions. Thanks to a
warm front, the temperature at 9,000 was
5 degrees C. As my destination drew near,
Boston Center cleared me from 9,000
to 7,000 feet, and I reduced power from
about 65 percent to 45 to 50 percent for a
gradual descent. I did not apply carb heat,
possibly because I never understood how
important this was in the letdown phase,
or possibly because I did once understand
but was rusty. In either case, the lesson
was immediately learned, since as soon as
I moved the throttle there was a loud pop

to VFR if that didn't work out. I ﬁgured I
could complete the return leg VFR or, if
not, spend the night on the ground making new friends.
The departure from Lebanon was VFR,
and climbing through 6,000 I started to
go into clouds. Continuing the climb to
8,000, I got a ﬁrst quick burst of light
rime that put me into the I-am-payingattention state, and then I picked up a
second short but more intense burst. I
had had enough fun. While still at cruise
power as I was about to ask Boston Center
for 6,000, the engine suddenly unwound.
Unlike the previous pop and loss of power
incident, this felt as if I was smoothly but
quickly reducing power to almost idle.
My sense was that as serious as the ﬁrst
encounter was, this was worse, and my
eyes started focusing on terrain below
the broken layer. Fortunately, carb heat
once again saved my bacon, and I was able
to continue the ﬂight at 6,000 with no
further airframe icing (temperature was
hovering around zero). I ﬂew the remaining two hours with carb heat on and was
happy to accept the performance and fuelburn penalty.
As soon as I was able after returning, I
reported the incident to our ﬂight safety
board and also corresponded with Gene
Benson, whose wisdom I have gratefully
received in various AOPA-sponsored
webinars. I learned that I was in a much
more hazardous carb ice regime than
I understood and the PA-28 can be
particularly problematic. I also reviewed
FAA literature and accident reports. The
positive here was that my instincts were
good and I did not fall prey to the all-toocommon trap of applying carb heat and
then backing it off too soon. The bad news
is that had I been more attuned to recent
knowledge, I would have been better
aware of the risks during my ﬂight.
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Flight Training - December 2014

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