October 3, 2007 By Steve Leslie
Cold-Weather Flight Operations
A pilot faces
many challenges in winter flight operations, so it is essential to have
a complete understanding of the hazards associated with winter weather.
Although there are countless factors affecting cold-weather flight
operations, three of the most commonly encountered are aircraft
deicing, cold-weather altimeter errors and runway braking action.
As for the first factor, a contaminated aircraft presents a serious
hazard that can result in degraded lift, unpredictable flight
characteristics and loss of performance. Canadian Aviation Regulations
state: "Takeoff is prohibited when frost, ice or snow is adhering to
the critical surfaces of the aircraft." The pilot-in-command is
ultimately responsible for ensuring the aircraft is free of frost or
other contaminants prior to takeoff.
Frozen contaminants are removed from an aircraft by using freezing
point depressant or de-icing fluids. These are specifically formulated
to shear or flow off an aircraft at liftoff and are based on the
rotation speed (Vr) of the aircraft. De-icing will provide the aircraft
with some protection prior to takeoff, but this is a very inexact
science and dependent on weather conditions at the time of de-icing.