So Qantas had a sudden decompression a few weeks ago, and now a Ryanair Boeing 737-800 has just suffered one.
Sudden decompression is one of the two types of event that can occur on any passenger flight that are certain to scare the hell out of almost anybody on board, even though they normally contain little or no risk to life and limb.
The other frightening event is an unexpected go-around late on final approach to land. Both that and decompression are fairly rare, but either or both might reasonably happen at least once to anybody who does a lifetime of frequent flying.
The terror factor in these events is a result of their sheer suddenness, and the fact they are totally unexpected (even by the crew who are reacting fast to a situation not usually of their making), and both these types of incident make the pilots so busy for several minutes that they cannot safely take the time to explain what has happened and reassure the passengers there is no risk.
First, let’s picture the go-around situation: the aircraft is getting so low on its approach to the runway that the passengers are watching buildings and landscape zip past, and they are mentally preparing themselves for the touchdown; this is white-knuckle time for a high proportion of passengers on any flight. Suddenly the engines roar, the nose pitches up, and the aircraft is climbing fast, and the worrying whirrings and clunkings of the gear being retracted and the flaps adjusted can be heard loud in the cabin.
No explanations from the pilots are possible because they are concentrating hard on making the aircraft safe, and working with ATC to ensure there are no traffic conflicts caused by this sudden change of trajectory. The cabin crew have no idea why the go-around decision has been made, so they are just as surprised as the passengers. The reason can vary from the failure of an aircraft that landed ahead to clear the runway quickly, to the crew being unhappy with the stability of their approach in stormy weather.
Now sudden decompressions. These are terrifying because of the sheer drama.
Depending on what has caused the decompression (see the blog on the recent Qantas event) there may be a lound bang followed by a whooshing sound as the air rushes out of the cabin; instantly, the passengers’ oxygen masks drop from the overhead racks, and fog forms in the cabin air because (remember your physics at school?) decompressing a gas causes a temperature drop, so the moisture in the air condenses into water droplets. The pressure drop will hurt everybody’s ears badly, and anybody who has a serious cold may suffer ruptured eardrums (they will eventually heal, I am reliably informed).
As if that were not enough, the pilots, who have had also to don oxygen masks and suffer the same pain, have to put the aircraft into a rapid descent to get down into more dense air before the emergency oxygen supply runs out.
During this emergency descent they have to communicate closely with ATC who are trying to help them to avoid collision with all the aircraft at lower cruising levels; simultaneously they are having to control the aircraft’s speed to ensure it does not exceed the allowable maximum, while navigating to ensure they don’t hit any mountains buried beneath the cloud layer they are flying through.
That’s not all. They also have to change their navigation plans to divert to an airport that’s not the one they’d planned for, which also means checking their charts and reprogramming their flight computers for the approach to the diversion airport. Simultaneously they are trying to do a diagnostic job on what caused the decompression, because they have to assume it may have damaged the aircraft’s structural integrity, even if it has not.
And you expect a reassuring message while that’s going on? Forget it. Even if they gave you one you wouldn’t believe them – you know you’re going to die, and that’s it.
But what about the cabin crew? They, too, have to don their oxygen masks and, because of the steep descent, they ought to strap into their seats – although some don’t because they are trying to help the passengers. Unlike the pilots’ oxygen masks the cabin crews’ don’t have microphones that connect to the cabin address system, and even if they did the cabin crew don’t know what’s gone wrong so they can’t explain it, even if they do recognise that what’s occurring is a controlled emergency descent. Some of them, like the passengers, also believe they are going to die.
Finally, about the emergency oxygen supply: it’s a trickle of pure oxygen designed to increase the proportion of oxygen in the air the passenger breathes. It is not a rush of oxygen that fills the bladder on the supply tube.
I’ll probably get murdered for telling you this, but even without donning an oxygen mask, a fit young person who doesn’t smoke would probably not suffer unconsciousness during the brief period it takes for the aircraft to get down to below about 20,000ft. Anyone who did suffer unconsciousness would be unlikely to have brain damage, because they would still have been breathing air, even if at a pressure that did not sustain their brain at a fully functioning level, and the unconsciousness would have been so brief.
Just get used to the reality. Go-arounds and sudden decompressions are seriously frightening, but hardly ever dangerous. The only people who love them are journalists.