Aircraft tyres lead a funny old life. They begin as sap in a tropical tree and end up as black streaks on runways all around the world. They need to go as fast as a racing car while each one supports the weight of two fully loaded double decker buses. They go from take-off in a hot climate to spending hours in an unpressurised and freezing cold wheel bay. And then we get them back out again to hit the ground with almost unimaginable force. In an effort to find out more, we hung out with some of the people who care for these incredibly tough and important parts of our aircraft, making sure they continually deliver fantastic levels of safety and reliability. Tyres, boring? We don’t think so.
Meet our tyre team
Conrad Lowen – Senior Design and Development Engineer
Conrad makes sure the wheels and brakes on our 747 fleet are in tip top condition and comply with all safety regulations. Conrad and his team work with suppliers and manufacturers to ensure optimum performance from the many components that make up the wheel and brake assemblies.
Darrell Thompson – Certifying Engineer
Darrell Thompson started with us as an apprentice in 1996; he meets our aircraft when they land and inspects all the tyres, checking for wear as well as any damage. He also checks the tyre pressures – normally done through the instrument panel on the flight deck – and makes the call when a tyre needs to be changed. For our Gatwick team, with 8 747s and their 144 tyres, that call comes on most days.
Tyre change experts Stephen Aldridge, Hitesh (Tesh) Magecha, Bernard ( Chippy) Chipchase.
Our Line Engineering Technicians and Maintenance Assistants are the people who do the actual wheel changes. The process isn’t dissimilar to a car wheel change but on a much bigger scale, with wheel change kits loaded up and ready to use for the start of every shift.
Our pilots also play a big part in keeping our tyres in good condition. Taxiing is a highly skilled operation where gentle steering and brake action can make a big difference to the life of the tyre.
From humble beginnings
Tyres begin their lives, as they have done for decades, not in chemical plants but in rubber plantations around the equator. Here the age old process of tapping the trees and collecting the latex in small cups still provides the raw materials for our tyres.
All the major tyre companies have their own plantations but can buy extra from independent growers who trade on the Singapore Rubber Exchange. The latex then makes its way to the factory in Japan where it’s treated and made into tyres before being shipped to our tyre shop. This is run by UTC Aerosystems in Hemel Hempsted who fit the tyres to their rims and send them to our hangars.
Aircraft tyres are designed to have new treads attached up to seven times. The retreading of our Bridgestone tyres happens at a high tech factory in Belgium, where a production line of sophisticated machines (and expert human skills) inspect and prepare them before a new layer of rubber is added on and bonded into place. The tyres are then tested using a process called Shearography which uses laser light to detect microscopic changes in the interior of the tyre. A tread will typically last for around 180 landings although many factors can affect their lifespan. One of the most punishing demands for aircraft tyres is the ground taxiing which can exert huge side pressures. Tight 360 degree turns at the end of some runways, particularly in the Caribbean, can also shorten the life of the tyre.
Wheely interesting facts about tyres
- A 747 main wheel tyre weighs 125kg and there are 18 on each aircraft.
- We used around 700 tyres on our 747 fleet in 2015
- Despite the spectacular cloud of rubber smoke when an aircraft lands, it’s actually the take-off that causes most stress on a tyre. With full fuel tanks the aircraft is heavier and the pushback, taxi and higher take off speeds create bigger forces on the tyre.
- Tyres are filled with nitrogen to around 200psi (pounds per square inch). Nitrogen is used because at altitude the tyres are subject to extreme cold, and water vapour in air would freeze.
- Our team can change a wheel in 20 minutes and on the 747 this can be done while passengers and cargo are being loaded and unloaded. We reckon with 455 customers on a 747 that is 2.6 seconds per customer. Nearly as quick as a Formula 1 team who change the wheel of one person in 2 seconds.
- Latex is naturally white and perishes easily in sunlight. A process called carbonising makes the rubber incredibly durable. It is this process that makes tyres black. And for those of you hoping to pick up a few facts for your next pub quiz, the Latin name for the rubber tree is Hevea Brasiliensis
- Although most aircraft take off at around 180mph the tyres are built and qualified up to 235mph. This allows a safety margin for occasional high speed take-offs from hot and high airports
- Tyre rubber can be recycled into low grade rubber products such as flooring, mud flaps or plant containers. The tyre companies are always looking for new ways to recycle rubber.
- We use Bridgestone tyres on our Boeing fleet and Michelin tyres on our Airbus fleet.
So next time you’re sitting on an aircraft as it lands, spare a thought for all the people, processes, development and science that go into making these modern day wonders and for the thousands of safe landings that happen every month thanks to their efforts.
A happy retyrement
After such a hard life we thought it was appropriate to offer an aircraft tyre a gentle retirement. Jeff Togwell at Bridgestone kindly donated a 747 tyre which had failed its shearography test (you know what that is now don’t you?) We’ve turned it into a herb pot outside our training centre in Crawley, giving our people a chance to view this engineering marvel close up while picking a few sprigs of herbs to spruce up their dinner.
Is there any part of our aircraft or our operation that fascinates you? Let us know what you’d like us to talk about in the comments section below.