AOPA Pilot Magazine - January 2019 - 82

P&E

PROFICIENCY
(SLDs) will then freeze on contact with
any unlucky aircraft.

The entire leading edge of each rotor blade
had about an inch of ice, making the blades
so aerodynamically inefficient that full rpm
at flat pitch wasn't possible.

icing products (CIP and FIP), pilot
reports, and all other standard weather
briefing charts and products. A pirep
should only be used as confirmation
that a positive icing condition exists; if
a pirep reports negative ice, that doesn't
mean another aircraft won't encounter it.
Different aircraft can react differently to
ice accumulation in the same conditions.
If unsure and all the charts seem overwhelming, sometimes it's good to talk to
a flight service briefer.
DETECTION

Airframe ice accumulation causes many
problems. It adds weight to the aircraft,
degrading performance and possibly
changing the center of gravity, and
creates aerodynamic inefficiencies when
adhering to surfaces such as horizontal
and vertical stabilizers, and rotor blades.
Accumulating ice also can create flight
control issues by adhering to exposed
pitch change links and other flight
control components, such as the swash
plate. It can adhere to engine inlet areas,
obstructing necessary airflow and even be
ingested by the engine. It can accumulate
unevenly on the main and tail rotor
blades, creating an unbalanced condition.
Ice can shed unevenly, causing pronounced vibrations; ice slinging off the
main rotor can damage the tail rotor and
create a hazard on the ground.
Ice on the windscreen can interfere with pilot visibility as well as pitot
static instruments. The altimeter, vertical
speed, and airspeed indicators may show
anomalies, indicating icing in the pitot
static systems.
The lower corner of the front windshield, windshield wiper, or outside door
82 | AOPA PILOT January 2019

hinge are good places to watch for accumulation. During cruise flight, a slow rise
in required engine power might mean ice
is accumulating on the airframe, increasing the weight of the aircraft, and/or on
the rotor blades and creating aerodynamic
inefficiency. A rise in engine turbine temperature may indicate ice interfering with
the inlet. Low-frequency vibrations in the
airframe or cyclic and collective can indicate ice accumulating on the main rotor,
creating an unbalanced rotor. A higherfrequency vibration in the pedals can
indicate ice accumulating on the tail rotor.
Those flying aircraft with track and balance monitoring equipment will be better
able to track this.
The thicker the cloud from top to
bottom, the more vertical development
there will be within that cloud, and the
larger the moisture droplet size will be.
Larger droplets are a greater hazard in
forming ice that will adhere to an aircraft.
Clouds with vertical development that
are at freezing or just below freezing will
have large liquid water content, which can
rapidly accumulate on aircraft surfaces,
so pilots should be extra vigilant between
temperatures of plus 2 and minus 10
degrees C. These clouds will have larger
droplet sizes than a thin stratus cloud,
with droplets of greater inertia that are
more likely to adhere to an aircraft.
Freezing rain droplets are a million
times larger than a cloud droplet, and
so have a much more serious potential
for icing on the aircraft. Freezing rain is
where an upper level unstable air mass
has generated very large droplet sizes
that eventually become so large and
heavy they fall through a below-freezing air mass. Supercooled large droplets

SURVIVE

When looking at icing potential charts,
forecasts, winds aloft, surface analysis,
and prognostic charts, one should have a
good idea of cloud bases and tops, as well
as temperatures and frontal activity. The
pilot should monitor outside air temperature at all times, and note cloud bases and
tops during climbs and descents. Before
you launch, have several plans to modify
course and altitude in the event icing is
encountered. Monitoring temperatures at
different altitudes throughout the flight,
as well as cloud bases and tops, provides
a pilot with situational awareness should
icing be encountered and means of escape
becomes necessary.
If icing is encountered just after takeoff, a course of action may be as simple as
returning to land at the departure point.
In IFR cruise flight, a change of altitude
to warmer-than-freezing, or less than
minus 20 degrees C, temperatures may be
prudent, or a change of altitude to avoid
clouds.
Situational awareness and knowing the big picture are important on any
flight, but they are even more critical in
potential icing conditions, especially when
flying IFR. During VFR flight a helicopter usually has the option of landing more
expeditiously, without having to take the
time to fly instrument procedures, even
landing off-airport if necessary. There are
many times during IFR flight, especially
when offshore or over a mountainous
environment, where one is committed to
a course of action and doesn't have the
advantage of being able to land quickly.
Sometimes a longer route, offering better
conditions or more options, is better than a
shorter flight with greater exposure.
Where icing conditions are concerned,
it's critical to have multiple courses of
action available. Don't worry if plan A
doesn't work; there are plenty more
letters in the alphabet.
AOPA
MARKUS LAVENSON flies the Sikorsky S-92

and Leonardo Helicopters AW139 over
the Gulf of Mexico.
AOPA Pilot Magazine - January 2019

Table of Contents for the Digital Edition of AOPA Pilot Magazine - January 2019
