An Airbus video describes how the pilot of the crashed Germanwings flight could have been locked out of the cockpit by his co-pilot.
According to the five-minute explanatory clip, if an A320 pilot wants to lock the cockpit door to bar access to someone outside, he or she can move a toggle to a position marked “locked".
This illuminates a red light on a numeric code pad outside, and disables the door, keypad and door buzzer for five minutes.
With these functions disabled, the only way to make contact with the crew is via an intercom, the video shows.
The doors will then only open if someone inside overrides the lock command by moving and holding the toggle switch to the “unlock” position.
Were someone outside the cockpit to suspect the pilot might be incapacitated, that person would normally first try to establish contact via the intercom or by activating a buzzer.
But if those efforts were unsuccessful, a crew member has to enter an emergency code on the keypad outside the cockpit.
That code activates a loud buzzer and flashing light on the cockpit control panel, and it sets off a timer that unlocks the door 30 seconds later. The person outside has five seconds to enter before the door locks again.
Dominique Fouda, a spokesman for the European Aviation Safety Agency in Cologne, said pilots and co-pilots could legitimately be left alone in the cockpit if one of them had to leave for “physiological reasons".
He said: “Basically, unless they have a physiological need, they have to be in the cockpit."
