Planes that can land on water

WHO, WHAT, WHY?
The Magazine answers...

The plane, an Airbus A320, appears to have have hit a flock of birds shortly after taking off from the city's LaGuardia airport, before making an emergency landing in the river.

Keep wheels up for smoother landing. If possible, burn fuel to aid buoyancy. Raise flaps and face wind to cut speed. Keep enough speed to maintain lift. Keep wings straight. Raise nose to 12 degrees and lower tail into water.

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Captain Chesley Sullenberger III has been praised for his "masterful" landing, but how does a pilot safely attempt such a manoeuvre?

Although the likelihood of a waterborne landing is remote, all commercial pilots must undergo training for such an eventuality before qualifying. They are taught to follow a procedure - which, in its initial stages is similar to an emergency landing on solid ground. However, there may not be time in an emergency to follow it rigorously.

Having made a mayday call and alerted the cabin crew, those in the cockpit must ensure the undercarriage - the wheels - is retracted to aid a smoother landing and prevent warning sirens sounding as the plane nears the ground. The air conditioning would also be turned off to allow cabin pressure to match that outside.

There is an overriding need to slow down the craft. If there is still power to the engines and a wind of more than 25 knots, a pilot would be expected to fly into the wind to assist slowing. Wing flaps would also be fully extended. If there is time a pilot would be expected to burn as much fuel as possible, reducing the weight of the plane and so increasing buoyancy when it hits the water. On this occasion, however, the engines appear to have already cut out.

THE ANSWER

Plane must be slowed right down

Both wings must be level with the water

The tail is lower than normal

The flatter the water the better

As the aircraft nears the water, the pilot must try to continue slowing while, crucially, ensuring the aircraft does not "stall". In aviation the word has a different meaning to that in motoring, for example. Stall is an aerodynamic term which describes when wings lose their lift.

It's a difficult balancing act.

"You don't want to hit the water too quickly or the plane will break into pieces", says first officer Tom Hanks of DHL, who flies Boeing 757s for the courier company.

At this point, a lot depends on the weather. In the seconds before impact, a pilot must try to ensure the wings are level - a feat clearly achieved by Captain Sullenberger, says David Learmount, operations and safety editor of Flight International magazine.