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Feeling hot, hot, hot

by Joji Waites Head of Flight Safety

Hot weather can be a huge problem for those travelling by road or rail as roads melt and rails buckle. But as the UK basks in record breaking temperatures, passengers can be reassured that pilots are continuing to use their skill, knowledge and judgement to ensure air passengers get to their destinations safely and without delay – whatever the weather!

For people in the UK, 30 degrees-plus temperatures may seem pretty hot and this current heatwave could see the UK reach its hottest day on record with temperatures forecast to hit up to 41C (106F).

Aeroplanes are of course designed to be operated within a range of temperatures from very cold to very hot and pilots are rigorously trained to handle the variations. It is very rare for upper limits to be exceeded, but it can happen. In Phoenix, Arizona for example, when temperatures crept up above 48C some flights had to be remain on the ground. A solution in place in some hot areas is to ensure flights are scheduled at night to take advantage of cooler temperatures.

One problem associated with heat is that as air gets hot it becomes less dense meaning it gives less lift and less engine performance. Normally runways in hot countries are fairly long, especially if they are at any altitude as this also reduces the air density. In really hot weather pilots have to take this performance into account and may have to limit the weight of the aircraft to ensure it can lift off as expected. In that case, payload needs to be reduced and pilots will balance the weight of the fuel, cargo and passengers with the weather restrictions to ensure they get the lift they need. Heat can also affect things like brake cooling and in hot weather, care with brake use while taxiing needs to be exercised.

It’s not just technical effects of heat that pilots must consider, it’s also the effect on passengers and crew. There are some procedures for the cabin as aeroplanes can get very, very hot inside quite quickly. These would be things like closing window blinds, making sure the air vents are all on full and in certain cases using a special air conditioning truck to blow cold air into the aeroplane. Flight decks with the glass windows and avionics/electronics can also get very hot and uncomfortable, and again the use of air-conditioned air and plenty of fluids for the crew is required.

Of course, with spells of hot weather we can expect another weather phenomenon that requires pilots to exercise their skill and judgement – thunderstorms and lightning. Pilots will do their upmost to avoid flying in Cumulonimbus clouds (the ones that produce thunderstorms and lightning). During the day this can be done visually with pilots spotting clouds and avoiding them. At night or when flying in cloud, this avoidance is achieved by use of the weather radar and pilots will normally look to keep at least 20 miles from a storm cloud. How storms and lightning affects aircraft was answered in a previous BALPA blog but encountering these conditions is when pilots really earn their money!

It is rare for temperatures to rise so high that aircraft cannot operate and as the thermometer creeps up in the UK passengers can be reassured that pilots will continue to use training and experience to keep flights soaring as the temperatures do the same.