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Originally Posted by meritflyer 
Always the pilots fault..  |
Sometimes it IS the pilots' fault. This appears to be one of them.
This story is a media account of the events, and offers little detail to explain what happened.
First, there's the position of the Cabin Pressure Controller switch. 99% of the time it was likely in the AUTO position, and required no action on the part of either pilot. Although it's almost certain that one of the pilots was required to verify the correct position of this switch before flight, it's easy to see how it could be missed, and cause no problem. If the switch is in AUTO, but it's not verified to be in AUTO, it still works. If it's not verified the next flight, but it's in AUTO, it still works. If it's not verified in AUTO, but it's in AUTO, it still works. Pretty soon, a habit has evolved that fails to verify the switch in AUTO. Then one day it's not in AUTO - - it doesn't work.
So, what are the symptoms of the problem when it doesn't work? Well, as it happens, the Aural Alert that sounds when the cabin altitude exceeds 10,000' or so is the exact same Aural Alert that sounds when there is a problem with the configuration of flaps, landing gear, and throttles. If you attempt to takeoff with the flaps up, the horn sounds when you push up the throttles. Or, if you lower the flaps to a landing setting without lowering the landing gear, the horn sounds. Or, if you retard the throttles to idle (below a certain altitude, in some cases), the same horn sounds. It's not uncommon to hear that horn on every flight. In fact, it's likely tested during preflight.
So, you're climbing along, fat, dumb, and happy, and this horn sounds. What's your first instinct? As many times as I've been through the drill in the sim, my first instinct is STILL to check the throttles, flaps, and landing gear. I can understand how the pilots would focus on that, and ignore the other clues. It's easy to understand how a little annunciator light indicating the masks had dropped in the cabin could have been overlooked. It's not like a mask dropped in front of THEIR faces. So, they're preoccupied with this landing gear warning horn, maybe decide to get up and pull the circuit breaker to make it stop squawking, and before you know it, they're hypoxic.
Add to this scenario the fact that the only language they shared was English, and neither one of them spoke it well, and you have a recipe for disaster.
It's something to think about the next time you consider skimming through the preflight. The chain could have been broken right there.
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