TRACE
|
Ice becomes perceptible. Rate
of accumulation slightly greater than rate of sublimation. It is not hazardous
even though de-icing/anti-icing equipment is not utilized, unless encountered
for an extended period of time - over one hour.
|
LIGHT
|
The rate of accumulation may
create a problem if flight is prolonged in this environment (over one hour).
Occasional use of de-icing/anti-icing equipment removes/prevents accumulation.
It does not present a problem if the de-icing/anti-icing equipment is used.
|
MODERATE
|
The rate of accumulation is
such that even short encounters become potentially hazardous and use of
de-icing/anti-icing equipment or diversion is necessary.
|
SEVERE
|
The rate of accumulation is
such that de-icing/anti-icing equipment fails to reduce or control the hazard.
Immediate diversion is necessary.
|
As with turbulence, the pilot should include the time of
the icing, both when first encountered and last encountered, aircraft type,
altitudes involved, position relative to a readily discernible fix (ie
40 west of YQM) whether in could or not (for example when flying below
cloud in freezing precipitation), and the type of icing (rime, clear or
mixed), and the intensity, based on the above table. The aircraft type involved
is important, since moderate icing to a Piper Navajo might be insignificant
to a B747, while moderate to a B747 would certainly be of concern to a Piper
Navajo. Also, different types of aircraft respond differently to icing.
ATR42s don't react to favorably to moderate+ icing conditions, while I've
rarely heard a Dash 8, which is of very similar configuration, report severe
icing. You know if a Dash 8 calls it severe, it's pretty bad. Other conditions
can be reported as well that might help pilots. For example, if icing was
encountered on departure while climbing through a cloud deck, the base of
the cloud deck could be important to someone else flying in the same area
as his only way of getting out of the ice might be to get underneath it.
The outside air temperature during the icing encounter could be important
as well as it may give a pilot an idea of where the freezing level is. See
below for more.