Nov 6, 2019

Flying in cold weather does present its own unique set of challenges for aircraft, ground crew and pilot, however there is much more to the circumstances around cold weather operations than the obvious issues with plummeting temperatures. Read on for the answers to commonly asked questions around flying in cold weather, the effects on the aircraft and taking off in extreme temperatures.

How Cold Can Planes Fly?

Plane Over MountainsEssentially the higher you fly, the colder it gets. If the temperature at ground level was 20 degrees Celsius, at heights of between 30,000 feet and 40,000 feet it would be between -40 and -57 degrees Celsius.

While we humans would not fare to well under these cold conditions, aircraft are built to handle all types of extreme weather conditions, and flying in cold weather is one of them. Rigorous flight tests are carried out well before the aircraft is released for general use, making sure all aspects of the aircraft will perform as expected under extreme cold.

Why Do Planes Fly So High?

Commercial aeroplanes usually fly at altitudes of between 35,000 and 42,000 feet, this is considered the ideal height range for maximising lift and reducing resistance and fuel usage and therefore costs. Heavier planes will usually find their optimal height is at the lower end of the range and lighter planes at the higher; each individual aircraft will have its own optimum altitude for each individual flight.

While reducing the costs of flying is always a factor (particularly with large commercial airlines on long-haul flights), flying high also provides the added benefit of avoiding the majority of the unsettled weather conditions that we experience here on the ground or in the troposphere (under 36,000 feet). Flying in the higher level or stratosphere means less turbulence, wind, rain and avoiding the danger of flying through clouds.

Can Planes Take Off In Extreme Cold?

DeIcing A planeFlying in cold temperatures is not actually the problem for most planes when operating in cold weather, the most common issue is de-icing the plane while on the ground. Ice on the wings or fuselage can increase drag, alter the lift properties of the wings – essentially changing the airflow patterns across these surfaces. De-icing is a necessary process in order for a plane to be able to take off safely.

Why is ice on the wings a problem? Aircraft are designed with specific aerodynamic properties based around the basic principles of flight – weight, lift, drag and thrust. Any alteration to these forces will alter how the aircraft handles during flight.

Even the tiniest bit of frost or ice can decrease the efficiency of the wings, and as a result require adjustments to all aspects of flight including fuel usage, takeoff speeds, turns and stall speeds. The de-icing process will depend on the aircraft and can involve heating, and the use of chemical substances. De-icing can take some time and is likely to cause delays.

Common Challenges Of Cold Weather Flying

Taking Off On Snowy RunwayOnce the plane is in the air and flying, cold temperatures alone are not as much of a factor as you would expect particularly when some planes are used to flying at temps of -50 degrees Celsius. In fact lower temperatures provide a more efficient flying experience because the cold air is much denser than warmer air. Once a plane is in the air its movement and speed keep its fuel, engine, wings and other working parts operational – often at a much higher temperature than that experienced externally.

So cold temperatures alone are not what prevents many flights from occurring during the wintery months, its when a plane is on the ground that many of the issues arise. Preparing for take-off under cold weather conditions can take its toll on the aircraft’s engine and moving parts, but can also have an impact on the all-important external conditions such as the runway and airport.

The Effects Of Cold Temperatures On The Aircraft

Extremely cold conditions can affect various working parts of an aircraft in a variety of different ways. Most commonly ice on the aircraft’s exterior is a major issue as any changes to the airflow can alter the basic aerodynamic forces during flight. However there are a few other things that can occur such as;

  1. Contraction Of Metals. Individual metal components including those made with steel and aluminium experience contraction issues, contracting at different rates under different temperatures causing potential issues when multiple parts of different compositions are required to work together.
  2. Fluids Freezing. Fluids or lubricants such as oil and brake fluids can lose fluidity increasing friction and wear and tear, and at extreme temperatures fuel can freeze.
  3. Parts Becoming Brittle. Components made from plastic and rubber parts sometimes become quite brittle and more easily breakdown leaving the aircraft incapable of operating.

When planes are kept in a hangar where fuel and general temperatures are raised they are able to operate in very cold conditions as this mitigates the likelihood of frozen aircraft parts and difficulties with starting the plane. In places where working in extreme cold is a common occurrence maintenance workers are well versed in the best ways to warm up an aircraft or unthaw frozen brake pads prior to flight, and how to operate safely within the limits of the aircraft – it is often a matter of time and efficiency which can lead to delays.

The Effects Of Cold Temperatures On The Runway

Some of the biggest challenges of cold weather flying come in the form of ice, snow and wind while on the ground, making working conditions treacherous and sometimes all but impossible. The main effects of extreme temperatures on the runway are;

  1. Slipping/Sliding. Ice or snow on the runway can mean it is too dangerous to land or take off, planes require traction just like the wheels of a car and if they strike patches of ice can slide uncontrollably across the runway.
  2. Poor Visibility.  Visibility issues associated with snow storms and heavy rain can mean workers are unable to determine if the runway is safe from obstructions and debris and on-site Air Traffic Control visibility can be reduced resulting in an unsafe landing zone.
  3. Freezing Working Conditions. Freezing conditions can also make refueling and aircraft turnaround procedures much more difficult if not impossible for the ground crew.
  4. Winds Too Strong. Strong or gale force winds commonly experienced in conjunction with snow storms or cold weather can also prevent aircraft from safely taking off or landing. See here for more information on the effects of wind on an aircraft during flight.

Cold weather flight operations are a frequent occurrence for countries such as Canada, Russia and parts of the USA, where temperatures can drop well into the negatives, however here in New Zealand we also have to be cautious of the effects of ice and snow on flying during the winter months.

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