Planes also spend about a week carrying out similar tests at high altitude airfields like Cochabamba and La Paz (Bolivia), Addis Ababa (Ethiopia) and others. La Paz is one of the world’s highest airports at 13,300ft (4km) above sea level, and Cochabamba is at around 8,300ft (2.5km) feet.

Using a plane at such high altitude airfields puts a huge strain on the engines and other systems. To test that everything operates smoothly, tests include several take-offs with all engines operating and with simulated engine failures, and the autopilot behaviour during automatic landings and go-arounds (aborted landings) is also checked. “The aim of such trials is to validate full functionality of the engines, systems, materials... and to ensure that the passengers, if ever in this scenario, are always in a comfortable environment,” says Dubon.

Wind tunnels, meanwhile, allow manufacturers to test all phases of flight – including extreme conditions. For instance, Boeing conducts tests at its Research Aerodynamics Icing Tunnel (Brait), says Adam Tischler, of Boeing’s Test & Evaluation department. It’s in there that the company inserts a cross section of a wing to test de-icing systems. The tunnel can test speeds between 60 and 250 knots (110kp/h to 463kp/h) in temperatures as low as -40C (-40F), says Tischler. The facility allows Boeing to simulate many kinds of rain, ice and cloud conditions that aeroplanes might encounter.

Virtual plane: Iron Bird

One of the most cutting-edge ways of testing modern planes involves building the guts of the aircraft on the ground and then testing these systems digitally. Bombardier, for instance, has built a ground testing facility called “Aircraft Zero” (Complete Integrated Aircraft Systems Test Area or Ciasta) in Montreal. It’s basically a rig that has all the key systems of a typical plane. It is used “to simulate an aircraft in flight virtually even before the actual aircraft takes to the sky” says Bomardier’s Sebastien Mullot.

The simulation uses high tech full aircraft system layouts on the ground called Iron Birds. “Iron-birds can simulate all flight segments such as take-off, cruise, landing, and so on, so that the aircraft is virtually tested on ‘real’ flights such as London to Dubai without any actual flight taking place,” says Mullot. “All this can be done well before the first pieces of the first aircraft to fly are assembled.”

The simulation helps anticipate any potential structural issues such as miniature cracks that could appear at a specific point of an aircraft’s service life, says Mullot.

It is even possible to virtually test for bird strikes on the cockpit and on the wing’s leading edge. “We can predict the structure behaviour according to any weight of the bird and any impact point,” says Jean-Louis Montel, deputy head of the design office at Dassault Aviation, a French aircraft maker. “This way, during the real test, a ‘calibrated’ bird is used and only critical impact points are tested.”

Engineers also carry out ultrasound tests on where the wing meets the fuselage; it allows to look inside the material and find possible defects without having to take the plane apart.

Lightning tests

On average, every commercial plane is hit by lightning about once a year, according to the Cardiff University’s “lightning lab” in the UK – a recently established laboratory where Airbus, for example, conducts lightning tests. The university’s lab is formally called the Morgan Botti Laboratory at the School of Engineering.