I’ve held off writing about the Air China flight which lost cabin pressure and quickly descended 21,000 feet because there were missing pieces to the story that just didn’t make sense. The incident was being blamed on a pilot smoking in the cockpit.
While it’s understandable that a pilot doing so wouldn’t want to be outed out of fear for their job, it was not clear how the smoking was in any way related to the incident. Until now, that is.
Flight CA106 from Hong Kong to Dalian, China was climbing to 35,000 feet while southwest of Shantou, China when the Boeing 737 initiated an emergency descent as a result of the loss of cabin pressure. Oxygen masks dropped. The plane leveled off around 10,000 feet, and then the crew brought the aircraft back up to around 24,000 feet.
— NDTV (@ndtv) July 13, 2018
The aircraft continued on to its destination, and landed safely around 3 hours after the incident in Dalian, China. The airline placed both pilots under investigation. They believed there was smoking going on on the flight deck, adn this led to the pressurization problem which then caused them to initiate an emergency descent.
So how on earth would smoking have done that? Apparently “while smoking in the cockpit the crew mistakenly shut down both bleed air supplies causing the cabin to lose pressure.”
The crew believed they lacked control over cabin pressure so brought the plane to a lower altitude. However they discovered, after leveling off around 10,000 feet, that they had just shut off the bleed air systems. They reactivated the systems, brought the cabin back to pressure, and climbed again to 24,000 feet.
Preliminary investigation by the Chinese Civil Aviation Authority suggests that the first officer was vaping with an electronic cigarette. Electronic or otherwise he didn’t want vapor or smoke to enter the cabin, revealing what he was up to, so he shut down the cabin re-circulation fan. He didn’t tell the captain he was doing it. Except that instead of shutting off the fan he shut down the bleed air. Oops.
And to potentially make matters even worse, when the plane descended it wound up in a dangerous trajectory in conflict with a private aircraft which then had to take evasive maneuvers.