Whenever bad weather, particularly snow, is forecast, it is only a matter of time before the inevitable headlines of “transport chaos” hit the news. As we are seeing at the moment, for trains, cars, boats and planes, only a small amount of snow and ice can cause delays and disruption, especially if people are unprepared.
But for air passengers there is a bit of hope. Airlines, airports and pilots work hard to ensure they have done everything they can to be ready for bad weather. The manuals, information and procedures required for cold weather operations are vast. Pilots undertake lengthy training that includes gaining an understanding of how to deal with adverse conditions and how to assess whether it is safe to take-off or land in poor weather.
In fact, the international dimension of air travel means we must be prepared to fly in areas that have much colder weather than here. I’ve operated in and out of some pretty cold places. Alaska, Canada, Northern USA and Scandinavia. The coldest I’ve operated at on the ground is -40 degrees celsius. But aircraft are pretty durable and routinely experience temperatures in the -60s at altitude.
Simulator training for pilots includes practising take-off and landing on contaminated runways. Pilots undergo ground school training and testing to make sure they know the procedures for adverse weather. We also check weather reports and local safety notices before each flight, so we can determine if it is safe to operate.
Like any vehicle, an aircraft in cold weather can get iced up and thanks to the supercooled fuel in the wings, frost can form insidiously even with temperatures above freezing.
The problem is that even small amounts of ice and snow can affect the airflow over the wings which could mean a reduction in lift. Serious amounts of heavy snow could also add weight to the aircraft or ice up moving parts of the wing and rudder.
Icing also can occur during flight. It can form on the wings and tail, along engine intakes and propeller blades, as well as on windscreens, probes, and various other surfaces. Left unchecked, heavy icing can damage engines, throw propeller assemblies off balance and steal away precious lift.
But all this has been well prepared for. There are procedures for de-icing, both on the ground and in the air. We have detailed guidance on when, and how to initiate de-icing.
On the ground, de-icing trucks spray the aircraft with a fluid that melts away ice and prevents further build up. In the air, certain parts of the aircraft are electrically heated to keep them clear of snow and ice, while other parts are kept warm through many mechanisms, including by diverting hot air from the engines.
Even planes that have been de-iced need to be able to get to the runways. So, if the snow is settling then taxi ways and runways will need to be ploughed. Airports work hard to shift snow and de-ice the runways to allow aircraft to continue to come and go safely. Places with a cold climate, that routinely face snow and ice, dealing with this weather is just part of the job. Many of these places are well equipped and are just brilliant at coping. They can clear a runway from scratch in 13 minutes. One pilot described dozens of big machines all working together, as looking rather like a ballet.
Because the runways need to be vacant while being cleared, flights can’t take off or land during this time, which is one of the things that leads to delays and cancellations as airports decide to reduce the total number of flights that day.
Taking off and landing on ‘contaminated’ runways requires the pilot to take note of weather reports and the condition of the runway surface to carry out complicated calculations, which will determine the aircraft’s performance.
One thing we don't fly in is freezing rain. If an airport is hit with rain or drizzle when temperatures hover near the freezing point, airport authorities will consider shutting it down and most definitely the airlines will start cancelling flights.
That’s because in such conditions, aircraft can gather ice faster than de-icing equipment can remove it. Ice can also wreak havoc on every other part of airport operations. An aircraft can lose traction in the ice, making it difficult to control. Critical equipment can freeze, and braking can become uncertain if not impossible.
But there is some good news. Aeroplanes actually perform better in colder, denser air because the wings generate lift more efficiently. They also produce power more efficiently. So, if it is just a snow flurry… no worry. A blizzard could cause some problems, but in most cases, if it is just a few snowflakes while there may be a few delays, but you should get away safely in the end.
Posted on 11 December 2017