Aero-Tips!
A good pilot is always learning -- how many times have you heard
this old standard throughout your flying career? There is no truer
statement in all of flying (well, with the possible exception of
"there are no old, bold pilots.") It's part of what makes aviation
so exciting for all of us... just when you think you've seen it
all, along comes a scenario you've never imagined.
Aero-News has called upon the expertise of Thomas P. Turner,
master CFI and all-around-good-guy, to bring our readers -- and us
-- daily tips to improve our skills as aviators, and as
representatives of the flying community. Some of them, you may have
heard before... but for each of us, there will also be something we
might never have considered before, or something that didn't
"stick" the way it should have the first time we memorized it for
the practical test.
It is our unabashed goal that "Aero-Tips" will help our readers
become better, safer pilots -- as well as introducing our
ground-bound readers to the concepts and principles that keep those
strange aluminum-and-composite contraptions in the air... and allow
them to soar magnificently through it.
Look for our daily Aero-Tips segments, coming each day to you
through the Aero-News Network. Suggestions for future Aero-Tips are
always welcome, as are additions or discussion of each day's tips.
Remember... when it comes to being better pilots, we're all in this
together.
Aero-Tips 04.21.06
Spring brings warming air in the Northern hemisphere. You might
think you’ve made it through another icing season, but beware
-- if you’re flying behind (or between) engines with
carburetors, it’s actually becoming more likely
you’ll face carburetor ice.
Carb Ice: The Threat
Carburetor ice forms when moist air enters the narrow carburetor
venture and cools to the freezing point, forming ice and choking
air flow at the throttle plate. Different carb designs have
differing characteristics that make them more or less susceptible
to icing at a given outside air temperature and humidity, but
there’s a growing hazard in spring as humidities "March"
upward and air temperatures "May" put you in the prime carb ice
range.
Source: Civil Aviation Safety Authority New Zealand
You can see there’s a "serious" danger of carb ice even at
cruise power settings when the humidity is greater than about 50%
and air temperatures run from just above freezing to as high as
60°F (15°C). There’s even a narrow range (in red on
the chart) where pressure-type carburetors (common in the 1950s,
and generally thought to be immune to carb ice) are
susceptible.
If your airplane has a carburetor air temperature gauge use
enough carb heat to keep the indicated carb temperature above
freezing. Note: I was very surprised that the
Carb Temp gauge in a Cessna 182 I often flew indicated freezing
temperatures in springtime and even summer cruise flight. If
your airplane does not have a carb temp gauge, be ready to apply
full carb heat at the first sign of reduced
propeller rpm or lower manifold pressure. Consider applying full
carb heat any time flying in visible moisture or when humidity
exceeds about 80% or so (in clear air).
Aero-tip of the day: As outside air
temperatures rise, be thinking about a different sort of ice
hazard. For more on carb ice see Aero-Tips 1.10.2006, "Carb Ice: All or
Nothing".