The cockpit voice recorder of Air Asia flight QZ8501 has been partially decoded, but there are challenges for the technical boffins according to the latest reports from Indonesia. That is trying to sift through audio saturation which occurs when a number of alarms sound inside the cockpit as the two pilots try and fathom what’s breaking and what’s going wrong. That can tend to be even more confusing. In the light planes I’m flying you often receive a voice warning or alarm. For example there’s the voice that says “Terrain” in an American accent if you’re a little low over a hill. Or the other which says “500” letting you know that you’re 500 feet above the ground as you descend to land.
Both can startle. But to have multiple alarms firing off at 32000 feet or so must be extremely frightening as you’re fighting a plane that is bouncing about or plunging towards the ocean. Picture the scene as the Captain and 1st Officer are overloaded as they begin to try and rush through emergency procedures – switching off alarms which immediately begin shrieking once more.
The way to replicate this is having very important people shout commands at you which must be identified while you try to recite a twenty-point checklist and hit buttons, simultaneously pointing a surfboard on a giant wave at a gap between two piers only slightly wider than the board itself while the board presses you backwards or forwards in multiple muscle-sapping G’s.
Part of the modern computer-driven plane is information overload, and in this instance, audio overload. Think about this.
The CVR (Cockpit Voice Recorder) has four channels feeding through into a single audio file. LHS, RHS, Intercom, Cockpit ambient sound. Then in each channel there’s Comms 1 & Comms 2, Nav audio, Ramp, Inter-Phone, PA, plus the audio warnings firing off. The most difficult ones to pick through are the voice and ambient sounds. Bits of plane crumpling and tearing off the superstructure while pilots problem solve.
According to one pilot on the rumour network, a complete CVR can take up to two months to decode given the multiple sounds compressed together. Add the cacophony in this plane because it was apparently stalling to the background alarms so loud the pilots can barely be heard.
An array of specialists has descended on Jakarta to try and pick through the audio files. Humans have problems assimilating noises from various sources simultaneously – even humans sitting on the ground with headphones on trying to pick up what two pilots are saying.
So when the alarms start sounding – and there are a few that could have gone off in the Airbus that morning – reactions vary. There are now two matters being discussed.
1) Why the pilot didn’t turn around if it was too dangerous to continue
2) What happened that led to the plane crashing
The technicians face a stressful time and won’t be thinking about this, they’ll be listening for exact words and alarms.
After all, you’re listening to dead men talking. In many of these cases, the authorities may even know the pilots concerned.
Then the stress of making sure that you’re 100% sure about what was said. The entire matter is not to be treated as if it was as easy as getting your secretary to transcribe two hours of chit-chat. It’s listening to the ghosts of our real aviation world, professional pilots, trying to stay alive while the monster they’re strapped to pitches them head first into a choppy sea.
Then the Flight Data Recorder information will be combined second by second with the audio file and, according to investigators, the initial report will be out on january 29th.
Then we should begin to find out what laws of physics Air Asia QZ8501 broke.
And who or what is to blame.
Desmond Latham 