Air scares

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.  

 

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8 Responses to Air scares

  1. kevin webster 27 August, 2008 at 9:37 am #

    I find your comments hard to fault technically.

    However why are there no pressure activated public announcements? There seems to be enough air molecules to extend life a little therefore sound will carry.
    Why don’t the crt’s dropdown or those in the backs of seats active to explain the situation?
    Millions of dollars are spent on airline advertising etc, why is so little spent on passenger reassurance?

    I hold a private pilots license and fly on commercial jets more than what I want and I was unsure if the rubber jungle bladders actually needed to inflate.!! Thank you for the info.

  2. David Learmount 27 August, 2008 at 10:17 am #

    Thanks for your response, Kevin. You’re the second person who has suggested a pressurisation-triggered automatic announcement since this blog was posted.

    Depressurisations can be very different according to their cause. If you read my earlier blog on the recent Qantas event, it describes – and shows pictures of – two very dramatic depressurisations. In the Aloha event the passengers would not have been able to hear an announcement, and in the United one those near the hull breach would not have been able to either.

    In the depressurisation I didn’t mention in the blog – the one in August 1985 that caused the world’s worst ever single-aircraft accident when the rear pressure bulkhead on a Japan Air Lines Boeing 747SR failed and took all the controls with it, killing 520 people – the aircraft didn’t carry out a rapid descent because the crew had lost all controls except those for the engines. It porpoised for more than half an hour before hitting a mountain top.

    Here’s a challenge for you and anyone else interested in the idea: suggest what the content of the depressurisation-triggered cabin announcement should be.

  3. David Nicholas 27 August, 2008 at 10:27 am #

    I posted this yesterday before DL started this thread, and it may be better placed here:

    So it’s happened again. An emergency descent following loss of cabin pressure (this time involving Ryanair), and it’s headline news (along the lines of “hundreds terrified in jet plunge”) and I have switched off all media until they get Chris Yates out of the way….
    Surprisingly, the most measured report I heard this morning was from Michael O’Leary himself, succinctly explaining that with the flight and cabin crew wearing oxygen masks as well, the explanatory cabin PA had to wait until the aircraft had completed its emergency descent (this in response to “many complaints” that “nobody told us what was happening”). Isn’t this precisely why the emergency briefing is given before takeoff (I wonder how many of the passengers paid attention to it)?
    There are not that many mainstream media hacks to bring up to speed on the basics of aviation procedures and safety. How about Flight International sponsoring a media symposium to explain the basics with the aim of minimising the abject nonsense (much of it speculative and alarmist) trotted out by the “Travel Editors” of most of our media organisations? So many people fly now that there is widespread public anxiety and even panic after serious accidents that even a precautionary turnback can make the headlines. Ahhhh for the days of “By Our Air Correspondent”……….

  4. Kevin Webster 27 August, 2008 at 2:37 pm #

    It is a difficult problem to keep 400+ people tranquil and informed while plunging down thousands of feet for a breath of fresh air. However I do believe that it is possible on those occasions when the depressurisation is caused by s small breech in the pressure hull or a technical malfunction in the pressurisation equipment.
    I agree with you regarding some of the incidents you quote, the noise would have been deafening and the dire visual inputs would overwhelm all but the brave and well trained. Any automatic safety information would have been ignored even if it had been heard or seen by the average passenger.
    However I believe the Qantas and Ryan Air incidents were nothing like the afore mention in severity. No doubt the cabin filled with water condensate, the aircraft would have pitched over causing a great deal of discomfort to all concerned especially if not seated and belted. No doubt the hard pitch over of the aircraft would cause a great deal of screaming from some for a short while.
    At some point after the event people would respond to a firm voice repeatedly telling them to:-

    PUT ON THE NEAREST MASK. PULL LEAD TO ACTIVATE AIRFLOW. DO NOTHING ELSE UNTIL YOUR MASK IS ON.
    PUT ON THE NEAREST MASK. PULL LEAD TO ACTIVATE AIRFLOW. DO NOTHING ELSE UNTIL YOUR MASK IS ON.
    NOW YOUR MASK IS ON HELP OTHERS. DO NOT REMOVE YOUR MASK.
    WHEN ALL IN YOUR LOCAL VACINITY ARE MASKED UP HELP OTHERS. DO NOT REMOVE YOUR MASK
    WHEN ALL IN YOUR LOCAL VACINITY ARE MASKED UP HELP OTHERS. DO NOT REMOVE YOUR MASK .

    Message Should Repeat.
    Of course some passenger will not benefit from an automated message, but some will and the airlines would not have to defend themselves against charges of not doing anything. Naturally the crew would cancel the loud and forceful message when safe to do so and take charge. Please note, I am not an expert in anything aeronautical or medical just a regular Joe who can fly a little and travels a lot.
    To be honest I do worry about business and frequent fliers like myself when confronted with a serious depressurisation problem on a long distance flight.
    (assuming a large breach in the pressure hull)
    Out of the blue the cabin fills with what looks like smoke. Its not, it’s water vapour. Paper, dust, pillows fly through the cabin, you have just polished off a G&T and nearly a bottle of red. Your shoes are somewhere and your wife has left her tray with you whilst she visits the toilet. One of the kids has followed her and the last you know your most precious thing was talking to a F/A beside the galley.
    You have the mask in front of you, you know hypoxia will get you but the wife and kid is missing!!!!!!!!!!!!!

    Just my thoughts
    Kev

  5. Robin Peacock 27 August, 2008 at 3:01 pm #

    Hello David
    I hear that BMI had a cracked windscreen and subsequent emergency decent last week but see nothing of it in the press. Any news on that?

  6. John Hoyte 27 August, 2008 at 3:28 pm #

    David,

    Spot on summaries of a Go Around and a Decompression.

    The one mystery of decompressions is why the pilots do not get a drop down O2 mask like the passengers but have to ‘work out’ that they might need one and then manually put it on?

    Maybe there are such systems, but I only knew the manual type, which seemed like an accident waiting to happen.

    Any thoughts for a bit of assistance – at time of high stress?

    JH

  7. Harry 29 August, 2008 at 7:04 am #

    The only reports i read into air crashes and accidents are the ones provided by the NTSB, AAIB and such like…

    I avoid all tabloid fables at all costs because they “Do My Head In!!!”

  8. Mike 1 September, 2008 at 12:42 am #

    “suggest what the content of the depressurisation-triggered cabin announcement should be”

    Just make it the same as the pre-flight safety demo!
    Ladies and Gentlemen, the cabin has lost pressurisation and masks have been presented in front of you. Stop screaming, take the mask nearest to you and put it over your nose and mouth and secure with the elastic as you were shown in the preflight safety demonstation. Attend to your own mask before attempting to help others. (Repeat 5x)

    WHAT? But they already told people that during the preflight demo! So what – no one really listens to that anyway. Tell them again and keep telling them so they get it right.

    You’ve got a wide range of people on the plane and their reactions are going to be one of shock, surprise and confusion. Some will know exactly what to do, others will panic and do the wrong thing. It’s just human nature.