How Things Work: Stopping the A380
Hint: Plan ahead.
- By Mark Huber
- Air & Space magazine, August 2011
(Page 2 of 2)
To stop the A380, enormous composite Honeywell brakes on 16 of the 20 main landing gear wheels do most of the work. As on most new airliners, the A380’s brakes are anti-skid. They work like the anti-skid brakes in your car, responding to extreme pressure by automatically pulsing to prevent brake lockup and skidding. Almost as important is the aerodynamic braking of 16 giant wingtop spoilers swinging skyward to create drag and reduce lift. Reducing lift improves mechanical braking by putting more weight on the wheels.
Of course, it’s the overall design of an airliner that allows it to slow from a transonic cruise at 500 knots to a crawl in a matter of minutes. Although enormous, the A380 lands just like any other Airbus of the A320 or A330 family, says Airbus executive Larry Rockliff, who has flown the aircraft for 120 hours. Letdown starts at cruise altitude at a speed near .85 Mach. Pilots enter data such as runway winds into the redundant flight management systems and compare data during descent to ensure accuracy. Below 10,000 feet the aircraft must be slowed to about 250 knots, and it generally enters the landing pattern at 180 knots. Pilots can manually control the rate of descent and speed by using knobs on the autopilot control panel, or can let the flight management system operate according to the optimum profile.
The design of the A380’s wings, with their large area, comparatively gentle sweep (33.5 degrees), and massive flaps, give the Airbus a landing speed that is 20 knots slower than that of a 747. An A380 crosses the landing threshold at a docile 140 knots and touches down, depending on its landing weight, at a speed as slow as 130 knots, about the same touchdown speed of some corporate jets that weigh 1/50th as much as the world’s biggest airliner.
Frequent contributor Mark Huber has been fascinated with aircraft stopping systems ever since he botched a landing as a rookie pilot, frying the brakes and bald-spotting the tires on a Cessna 172.