As an airline, of course we’re all about flying – but it goes without saying that we can’t do that without first getting up into the air and then down onto terra firma again. That’s why an aircraft’s undercarriage (aka landing gear) – made, by the way, by specialised manufacturers, rather than Airbus and Boeing – is so absolutely critical to our aviation systems, and we take meticulous care to keep it in optimum working order.
What Comprises Landing Gear?
The landing gear’s main function is to absorb the impact of landing to keep the fuselage from hitting the ground. The gear’s main strut has a hydraulic shock absorption system, regulated by compressed fluids, and the impact of landing is also over up to 12 wheels, each with a separate braking system. The anti-lock braking system (ABS) found in all road vehicles was first tested in aircraft landing gear (thus the brakes we use in our cars every day we owe to aeronautical engineering). Each wheel also has 11 pieces used to control the progressive braking of the aircraft, assisting the brake disks in reducing the speed of the wheels without allowing them to seize up. Individual details will of course vary to a certain extent depending on the aircraft type and model.
Wheels Up – and Down Again
Controlled by computer, the shock absorbers are retracted and the landing gear raised quickly into the body of the aircraft after takeoff – as soon as a “positive rate of climb” is achieved – so as to reduce air drag and allow the aircraft to gain speed.
Then when it comes time to land, the gear is lowered – also computer assisted – once the aircraft has reached a certain speed, typically around 280 knots (nearly 519 kilometres per hour/322 miles per hour); there’s also a backup system involving electromagnets.
Testing, Testing…
It goes without saying that as part of our rigorous régime of aircraft maintenance, landing gear always plays a crucial role. So frequently our expert technicians at Iberia’s maintenance Hangar 2 in the town of La Muñoza, next to Barajas Airport, painstakingly examine and test the sets attached to various members of our fleet, scheduled according to hours of flight time and numbers of takeoffs/landing; the older the aircraft, the more frequent this testing. After the paperwork and maintenance personnel are assembled for each, the aircraft is put on hydraulic jacks; all shock absorbers replaced; all systems inspected carefully for defects (including any connection issues with warning lights in the cockpit) and the landing gear is put through its paces, including gravity tests in which the hooks holding the landing gear are released, allowing it to drop under its own weight, without hydraulic action (this is part of an emergency system that allows it to be deployed for landing in the event that the aircraft somehow loses hydraulic pressure).
The testing also involves lowering and retracting the gear at least ten times, says production manager Juanma Rivas. The tests are repeated several times with all wheels touching the ground after the aircraft has been removed from the jacks, then if it gets the all clear, it’s towed out to be returned to service; if landing-gear repair is required, the aircraft instead is transferred to a nearby authorised shop, where the process takes about a week.
It’s an impressive sight indeed – and a testament to our commitment to passenger safety.
photos/video | José Balido, Soledad Moreno Herreros