Icing Intensities And PIREPS
Weather personnel cannot generally observe icing; they must rely on PIREPs. When flying
during icing conditions, pilots should report these conditions as indicated in Figure 5-13.
However, forecasters attempt to forecast the maximum intensity of icing that may be
encountered during a flight, not necessarily the intensity of icing encountered by a particular
aircraft. It becomes the pilot's responsibility to make certain a complete weather briefing is
obtained, to include the information for safe completion of the flight.
Airframe Ice Accumulation
Ice becomes perceptible. Rate of accumulation
slightly greater than rate of sublimation. It is
location, time (GMT),
not hazardous even though deicing/anti-icing
altitude (MSL), type
equipment is not used, unless encountered for
aircraft, sky cover,
an extended period of time--over one hour.
visibility & weather,
The rate of accumulation may create a problem
turbulence, icing, remarks.
if flight is prolonged in this environment (over
Example of PIREP
one hour). Occasional use of deicing/anti-icing
equipment removes/prevents accumulation. It
does not present a problem if the deicing/anti-
icing equipment is used.
Rocket 501, holding 20
miles south of Navy
The rate of accumulation is such that even short
Pensacola, at 2100Z and
encounters become potentially hazardous and
one-six thousand feet,
use of deicing/anti-icing equipment or
single T-39 Sabreliner,
diversion is necessary.
we're IFR in stratus
The rate of accumulation is such that
clouds, temperature 15°C,
deicing/anti-icing equipment fails to reduce or
winds 330 at 25, no
control the hazard. Immediate diversion is
turbulence, Light Rime
Icing, flying 200 knots
Icing may be rime, clear, or mixed:
Rime ice Rough milky opaque ice formed by the instantaneous freezing of small
super-cooled water droplets.
Clear ice A glossy, clear or translucent ice formed by the relatively slow freezing of
large super-cooled water droplets.
Mixed ice A combination of rime and clear ice.
Figure 5-13 Icing Reporting Criteria
Weather Hazards of Turbulence, Icing, Ceilings, Visibility, and Ash Clouds