Air China Flight 106, a Boeing 737-800 traveling from Hong Kong to Dalian, dropped from 35,000 feet to 10,000 feet within 10 minutes earlier this week. The question is, why?
Ostensibly the answer is because the flight lost pressure in the cabin. But why did the cabin lose pressure? That’s where the issue becomes more complicated. The incident occurred about 30 minutes after takeoff. After deploying oxygen masks and dropping to 10,000 feet, the aircraft began climbing again and continued to its final destination.
This leaves me with two questions:
- How did this de-pressurization occur on a relatively new 737-800?
- Why did the pilots not divert, out of an abundance of caution?
The two questions may be linked by one word: smoking. At least that’s the word from People’s Daily, a state-run newspaper in China that cites unnamed sources to report that the pilots had been smoking in the cockpit.
Remember that flight deck side windows open. Did one of the pilots attempt to extinguish cigarette through a window? Or could excessive smoke or a fire in the cockpit have prompted the window opening? Opening a window, even a crack, could certainly have led to the depressurization. A cockpit window is not like an aircraft door, where intense pressure at high altitudes makes it virtually impossible to open thanks to the locking mechanism on it.
I’m surprised the pilots did not divert. After 12-15 minutes, all the oxygen was gone from the passenger air masks. Did pilots forgo a diversion into order to hide evidence of smoking?
A Second Scare
Toward the end of the flight, FAs made an announcement to put the oxygen masks back on. Small problem: they were empty. It turned out to to be a false alarm, but had it been a real emergency there was no oxygen inside.
Air China is taking the matter very seriously. It has stated:
If the investigation reveals that the crew has violated regulations, the company will seriously deal with the responsible person with zero tolerance.
Apparently, Air China regulations prohibit crew members from smoking onboard, even in the cockpit or crew rest areas.
UPDATE: It Was Smoking!
Chinese authorities have now confirmed smoking is to blame for the incident:
A senior official from the Civil Aviation Administration of China (CAAC) told reporters Friday that, without notifying the pilot, the unnamed co-pilot was trying to turn off air recycling fans to prevent the vapor from spreading into the passenger cabin.Instead, he toggled the wrong switches, which were close to his intended target, leading to a drop in oxygen levels which triggered altitude warnings.Qiao Yibin, the CAAC official, promised to hand down “severe punishment in accordance with laws and regulations,” if the regulator’s final conclusion on the incident matches its initial finding.
CONCLUSION
As One Mile at a Time did, it’s fair to mention that it’s not like the aircraft was ever free-falling. But a 25K foot drop in 10 minutes is off-putting, to say the least. Having been on a China Eastern flight that smelled like an ashtray, I hope that if the pilots were smoking, they will be dealt with harshly. More broadly, the Civil Aviation Administration of China should take additional steps to dissuade pilots from lighting up onboard.
My biggest concern is that the captain put all 153 passengers at risk by failing to divert because of the depleted oxygen. Had another emergency occurred that required oxygen, passengers would have been up the creek without a paddle. That’s a sobering thought far more important than the smoking issue.
Am I fair to question the pilots here, regardless of the cause of the depressurization? Would you fly Air China after this incident?
image: Weibo
“A cockpit window is not like an aircraft door, where intense pressure at high altitudes makes it virtually impossible to open.”
Impossible to open? Pressure is much higher inside than outside the cabin. If someone successfully opened the cabin door mid-flight, the doors would fly open. The only reason the cabin doors can’t be opened mid-flight is because of how tightly they’re locked and sealed.
Good point – I’ve clarified that in my post.
Well George Kennedy seemed to just pop open the cockpit window on the Concorde in Airport ’79….so perhaps the pilots were shooting off a flare gun to avert a missile that was launched from North Korea?
Cockpit windows and cabin doors/windows are plug type openings. They are called this because the pressure inside the cabin pushes the door against the frame acting to seal it shut. Because of this it would be impossible to open a cabin or cockpit window or cabin door in flight as you would have to overcome the pressure on that door/window to open it. Its not a question of the locking mechanism it the basic design of the door which makes it impossible to open.
2500 foot per minute descent is not terrible. Over dramatized article for a non event. I wear oxygen masks on a routine basis in my Cessna 206.
You don’t think flying for three hours without any oxygen in the masks is a problem?
It a major problem and should not have been done especially since they climbed back up to altitude. Had there been a decompression on that flight pax oxygen having been depleted would not have been available. The moment the rubber jungle comes out as a matter of safety your committed to flight at or below 10,000 feet and a diversion to the nearest airport.
Don’t forget too that oxygen generators create a lot of heat which has the attendant possibility of fire. That shouldn’t happen but it is a risk and certainly argues against continued flight.
Maybe you should check on reuters and China news quote:
““Smoke diffused into the passenger cabin and relevant air conditioning components were wrongly shut off, without notifying the captain, which resulted in insufficient oxygen,” it quoted Qiao Yibin, an official of the regulator’s aviation safety office, as saying. China News said the co-pilot had shut off the air conditioning units.
so no window bur manipulation of the air conditioning
I had already included an update in my story. This vaping update, however, was made public after my story was written.
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Those pilots were probably taken to the end of the runway and summarily executed after this.