How An Airbus Cockpit Locking Mechanism Works [Video]

Post-9/11 plane tech points to a disturbing cause behind the Germanwings crash

Speculation abounds this morning over what brought down Germanwings Flight 4U 9525, which crashed into the French Alps on Tuesday. The Airbus A320 plane, en route to Düsseldorf from Barcelona, had just reached a cruising altitude of 38,000 feet when it began descending unexpectedly. Eight minutes later, it crashed into a mountainside.

Clues are emerging as to what might have caused the crash, and it now seems the accident wasn’t an accident at all. At a televised news conference in Paris this morning, chief Marseille prosecutor Brice Robin, who is leading the investigation, painted a rather eerie picture of the moments leading up to the crash. The flight recordings suggest the captain (whose name hasn’t been officially released) left the cockpit to use the restroom but couldn’t get back in. He gently knocked, then banged on the door. However, his pleas were met with silence by the co-pilot, Andreas Lubitz, who was still inside and may have deliberately activated the plane’s descent.

Robin cited other unnerving evidence, including the co-pilot’s steady and normal breathing up until the moment of impact, calling into question the idea that he might have suffered a medical episode.

What’s known about the cockpit door locking mechanism also suggests a voluntary act. Quartz found this video, which walks through Airbus reinforced door procedures:

https://www.youtube.com/watch?v=ixEHV7c3VXs?

Since 9/11, the aviation industry has made substantial changes to how a person can enter a cockpit. Specifically, Airbus–the manufacturer of the Germanwings-operated jetplane–modified their vehicles so the cockpit door remains locked at all times. If someone wants to enter the cockpit, such as a flight attendant, he or she must request access through an electronic communications system. The pilots can then open the door by flipping a switch to the unlock position.

But suppose, for a moment, that both the pilot and co-pilot became unconscious and couldn’t open the cockpit door. In this scenario, a flight attendant can punch a code into a keypad outside the door, alerting the crew inside that it’s about to unlock in the next 30 seconds or so. During this time anyone inside the cockpit can override the unlock function. “The locking devices on the latest planes can override that code assuming a hijacker found out the code,” Vernon Grose, a former investigator for the National Transportation Safety Board and former scientist for the Federal Aviation Administration, tells Popular Science.

This override feature has aviation experts suspecting the Germanwings co-pilot crashed the plane on purpose. Presumably, the locked-out pilot would have entered the unlock code into the keypad to get back inside the cockpit. And, barring a malfunction with keypad override, the door should have opened after roughly half a minute. Given that both a malfunction and a co-pilot medical emergency happening at the same time seems highly unlikely, an intentional act on the part of the co-pilot is, at this point, the most likely explanation.

“Everything has a plus and a minus when it comes to technology”

According to Grose, this scenario demonstrates a faulty “failure mode and effects analysis.” Such an analysis is conducted every time manufacturers put a new safety technology into an airplane. The goal: Determine all the cases in which the technology might fail. In this instance, either the aviation industry didn’t consider a situation in which a pilot might use the technology with malicious intent, or they considered it to be an extremely unlikely occurrence, figuring the benefits of such technology (preventing hijackings) outweighed the cons (enabling hijackings).

“Everything has a plus and a minus when it comes to technology,” Grose says. “The locking device is wonderful on one side if someone bad is trying to get in. But it’ll keep someone good out who needs to be in there.”

Grose and other aviation experts agree it’s too early to speculate on future countermeasures to thwart a cockpit-locking hijack, especially since information from the investigation is incomplete. However, if it does come to light that the co-pilot was at fault, it’s possible there will be some regulatory changes–in regard to how cockpit doors function, how background checks on pilots are done, or both.