Emergency Descent - 36000'
 

Fellas/Ladies,

Just a quick one to get your take on dealing with loss of cabin pressure at 36000'. I expect a lot of you browsing this forum have experience flying both military and civilian hardware and I'm looking for your perspective.

This is a second hand story from my father who was on board so the exact details are sketchy...

My parents were over France on a flight from Rome to Manchester this evening. Jet2.

The first my dad knew something was up was the Cabin Crew started to look concerned, looking at one of the cabin doors. They were on the phone a lot and then one of them started banging on the cockpit looking quite alarmed.

The next thing that happened was a very loud bang (the sound of the deploying oxygen masks, not an explosive depressurisation), the lights went off and then a very worried sounding captain or first officer almost screamed over the intercom "Emergency Descent" 5 or so times.

Panic obviously ensued as the plane bunted and dived for 10k. Oxygen masks full of dust and cobwebs and cabin crew looking like they were on the tower of terror and had little or no training (according to my angry Dad).

After the dive was over, the captain THEN explained that he had decided to deploy the oxygen masks manually and carry out an emergency descent. Based on advice from his airhosts or instrumentation I do not know, though anecdotal evidence of their reaction seems to suggest he may have acted independently.

I appreciate the above narrative lacks a lot of useful detail and I'm not looking for people to critique the captain's airmanship, mainly because by the letter of the law, getting down and letting the cabin crew know what was going on takes priority over not terrorising 150 odd unsuspecting passengers.

Have any of you had to rapid descend a big bird? If so, how drastic an emergency is it? If the crew consider there to be enough time to scream things like "emergency descent" over the intercom more than a few times do you disagree that there is time for them to take a few seconds for couple of choice words before exploding oxygen masks into passengers faces, killing the lights and bunting?

The first thing my dad said to me on the tarmac at Nice was "what would you have done?" to which I obviously responded with a Right Stuff Chuck Yeager line for the passengers. As I was not there and I have never been in that situation in a big jet this may very well be a bull%^&t answer...

What do you guys think?

It's a standard drill to be followed. Explaining to the passengers what is/has going on comes much later in the priority order.

The account you provided seems to mistake the Captain commanding his crew for panicking. (the wording over the PA will vary from airline to airline - but it is a command to the crew and not a passenger information announcement)

This may answer your question:

http://flightdotcom.********.com/201...ciousness.html

The link in my previous does not seem to be working. Google "Time of useful consciousness" and you will learn why speaking to the pax is way down the priority list.

Do you know what sort of an airplane it was?

Cabin doors are usually of the plug type, so extremely unlikely of opening in flight.

The screaming sounds unnecessary, although, the Passenger Address system on this aircraft may have been put into a maximum volume mode automatically by the deployment of masks. Real decompressions may result in a lot of extra noise and this has to be compensated for, but, from your description, it doesn't sound like there was a real decompression. Also, most aircraft are fitted with automatic emergency decompression announcements. Ours are loud, and speak in a "commanding", not screaming voice. However, manual deployment may not trigger the announcements on this aircraft type.

I don't know why the lights went off. On the aircraft I'm familiar with, the lights should go full bright.

Oxygen mask deployment should not generate lots of dust and cobwebs, but again, this could be aircraft specific :} The compartments for holding the masks should be dust free, otherwise this might generate a fire.

There is insufficient information to comment on the airmanship. Rapid descents, however, would make things rather busy in the cockpit. You will be descending rapidly through various flight levels where other aircraft may be, so you need to communicate your intentions to Air Traffic Control as well as communicate with the passengers and crew. The flight crew may have chosen to stick to their formal company training/procedures rather than make a polite, long-winded announcement of their intentions (for the sake of safety).

Unfortunately, despite their training, cabin crew sometimes do react like normal human beings. This is another reason why you should listen to the safety briefings and read the safety card, not your newspaper ;) "Do as I say, rather than do as I do".

Anyway, an official report has to be made after such events. Eventually the full details will surface in the public domain.

Rgds

Here is a generic emergency checklist for a Boeing in a situation that may well be similar to what your Dad found himself involved in that I grabbed off the net.
It may give you an idea of what the pilots were doing. Keep in mind that this is after they have decided that there is actually a pressurisation problem.


[quote1 Don oxygen masks and set regulators to 100%.

2 Establish crew communications.

3 Pressurisation mode selector . . . . . . . . . . . . MAN

4 Outflow VALVE switch . . . . . . . . . . Hold in CLOSE until the outflow VALVE indication shows fully closed

5 If cabin altitude is not controllable:

Passenger signs . . . . . . . . . . . . . . . . . . . . ON

If the cabin altitude exceeds or is expected to exceed 14,000ft:

PASS OXYGEN switch . . . . . . . . . . . . O][/quote]

After doing that and deciding an emergency descent is in order;

The bit that says " announce the emergency descent" isn't left up to the whim of the Captain as to what he or she says, it will be something along the lines of .....funnily enough " emergency descent emergency descent emergency descent" . The announce doesn't just apply to the passengers and crew, while that is being done the other pilot will be announcing to ATC and other aircraft.
One reason that it may sound like the Captain is " screaming " the announcement is that earlier on you would have noticed that oxygen masks were donned, the mic is enclosed and close to the mouth and can have this effect when combined with a heart rate of 150bmp :)
This may or may not be what occurred on your Dads flight but I thought it might help you see the order of priority that things are generally carried out in and make it a bit more obvious that adding in the odd " Chuck Yeager PA " can disturb the flow of things.
Hope that helps.

Personally I think they did a good job getting everyone on the ground safely. It always surprises me how people are angry after the event...

Quick look on flightradar reveals it was G-GDFH and diverted to Nice.
But ... it happened very shortly after departure and never made it anywhere near 36000 ft

Expanding on the theme somewhat, but connected; I'm interested in sounding out opinion. This is a rare manoeuvre and I have my own ideas how to do certain aspects of it, based on real-life events: not my own. I've done it in the sim numerous times, somewhat like a trained monkey and I'd like to hear different pilots/companies opinions.

Whatever the scenario it becomes necessary to make an emergency descent. Do you:
1. Mayday ATC and inform them you need an E.D. and wait for a clearance?
2. Hurtle on down and THEN inform ATC what you are doing?

Second question.

Do you:

1.Maintain max ROD until 10,000'?
2.Maitain max ROD until e.g. 15,000' and then 1500fpm easing to 1000fpm about 12,000' till 10,000'?

I'll keep my ideas hidden and look forward to hearing yours. Please be objective.

Oh! and please don't forget TA Only BEFORE you descend otherwise a TCAS RA to reduce V/S could be triggered. That too is a little hidden gem and often not complied with. When Boeing was asked why it was not in their QRH checklist there was stoney silence. What about other types and airlines? It is a Eurocontrol recommendation and makes TCAS sense.

Oh my god!
So much better to hit another aircraft than reducing your rate of descent.
Review the your aircraft oxygen time ....on the 737 its either 12 or 22 mins,on the 12 min uou can descend from 41000 to 17000 ft then level off for 5-6 minutes then to 10000 ft.
Beware of MSA higher than 10000 and temp correction...
Cncerning your emergency descent,
How many pilots in your aircraft?if more than one then one asks for descent while the other flies...you will get an answer very quickly,if not,broadcast on 121.5 and think of an offset if you are on an airway.


For the rate of descent,you use speedbrake and mmo/vmo (unless structural damage/then 280 kts and possibly gear down),for the level off just as your QRH says......

Concerning the emergency descent only:

1. Start emergency descent per AFM

2. Change transponder to 7700.*

3. Notify ATC, declare Mayday.

4. Checklist.

The above after donning the O2 masks obviously and some operators may have numbers 3 and 4 switched.

I've had four rapid decompressions, two in the 727 and two in a Lockheed Jetstar. Those were the procedures I followed, no issues with ATC about starting the emergency descent without notifying ATC before starting the emergency descent.

Follow the old adage of 'Fly first, talk later'.

Once I heard an American Airline aircraft that had to make an emergency descent, the first thing we and ATC heard was the FE reading the emergency descent checklist, pushed the wrong mic button. Only after the FE finished the checklist did they call ATC.

* In a radar controlled environment, 7700 will get the air traffic controllers instant attention.

Usually just a problem with the seal. Although the noise can be quite loud and disconcerting with the CC can be understandably concerned. But if the pressurization is normal (even if the door light is illuminated!), then all is well.

on the subject, should we ask ATC if they want us to squawk 7700?
remember many years ago on a visit to TRACON the controller asked a Delta to squawk it just to show me, and an EMERG tag replaced the whole data block losing the flight number.

Time of USEFUL Consciousness?
 

Ask ex-military aircrew who's done the advanced farting class at RAF North Luffenham or elsewhere, albeit under controlled conditions, and you might appreciate the priority is to get down to where the human brain can make sensible decisions with adequate O2.

Or maybe read the Helios accident report and ponder the ability of the advanced Bonobo chimp to survive in such a hostile (lack of) atmosphere?

Now that 737NGs and other craft are pottering around routinely at 41,000', please appreciate there's not a lot of time to fanny around whilst the cabin altitude rockets up to silly levels.

The adrenalin perceived in the F/Os voice is perfectly normal in such circumstances, even when being practised in the simulator, without the REAL fear associated with such an event.

Your relative is around to talk about it, for which we should rejoice?

AFAIK ( in the UK anyway) squawking 7700 is definitely "a good thing" because it may well alert the controller(s) running in the adjacent (as in lower) sector that you're about to plunge into their airspace.

UK advice here:http://www.ead.eurocontrol.int/eadba...2012-11-01.pdf

You wanna do WHAT??!

Come off it, below FL200 the decent is no longer critical, and below FL150 it's a bonus. Supplemental O2 makes this even better. Adjusting VS to avoid other bits of tin is ESSENTIAL.

Discussing the 7700 option last few times I've done this in the sim with my operator, we decided it was purely for bonus points. Rightly or wrongly.

Once established in the decent, safe, and on masks, you need to speak to ATC and get out your PAN/MAYDAY. If they subsequently want 7700, they will ask for it.

The thing about emergency descents is, they don't always ruin your day. A few that occurred in my company resulted in the flight continuing to destination, albeit at FL100. So it's a matter of balancing reason, damage, fuel burn, comfort, pax state, crew state, maintenance at dest etc etc...

As always in this game, it's safety vs commercial all the time. By if you don't have to land immediately, and 2 hours at FL100 is an option...... Just sayin

Why the concern over selecting TA Only? (@ Lovejoy)

If you really have decompressed, and perhaps have suffered some kind of structural damage, you wouldn't want an RA telling you to climb or carry out some kind of radical high G manoeuvre. Wouldn't you leave the dodging to the most able aircraft?

Based on the presented facts, a total overreaction. Locked doors cannot come open in flight. Deploy the masks just in case??

I've always been intrigued about this "announcing" the emergency descent. What is the point, apart from to your FO? What are the pax going to do apart from cr@p themselves (not having heard the term before)? What are the FAs going to do? Jump up and run around like headless chooks or simply grab a spare mask when/if one appears?

Given the manoeuvre should be smooth and be all over in a few minutes, surely the popping out of the masks (if indeed they do pop) will be enough "advice" to indicate to the masses in the cabin what is occurring and to do?

Why the concern over selecting TA Only?

If you really have decompressed, and perhaps have suffered some kind of structural damage, you wouldn't want an RA telling you to climb or carry out some kind of radical high G manoeuvre. Wouldn't you leave the dodging to the most able aircraft?

Firstly: it is a Eurocontrol specification. Secondly; with my limited knowledge of how TCAS really communicates in an intruder scenario: you are cruising relaxed in level flight. An intruder is hurtling towards you at high ROD. Who do you think will get the RA to move first? I suspect the high ROD will get an RA to 'reduce V/S'. I've asked the question to technical pilots and had no reply, hence my quest here. But, if it is true, my assumption, do you really want an RA telling you to adjust your Emergency descent?
Don't be jump down my throat too fast, I'm seeking the correct answer. In the decompressurised environment, with all the noise and reduced visibility, lousy crew communications etc. do you really want a moment of "what shall we do/confusion" telling you to reduce or stop your descent? Personally I doubt it. It is Oh so simple in the sim every 3 years; nice and clean and relaxed; but in anger I suspect very very different.

Regarding ATC clearance. As soon as you deviate 300' from assigned crz level radar screens will give an alert to ATC who will then start shouting at you to maintain level. You start shouting back with Maydays. Is this the best team work? What's the rush? There's enough O2. and you and pax should be on O2 before the E.D is commenced. I'd always thought good teamwork in an emergency required good communications. Does it really take more than a few seconds to include ATC in your scenario and then have a smooth relaxed executed manoeuvre with everybody knowing what's going on, with perhaps an ATC HDG change, rather than appear as a surprising bowling ball hurtling at skittles vertically below you and asking ATC to sort it out. There's no panic; and you could make a bad situation worse.

It's a discussion point guys. I don't believe there's black & white. There will be many diverse opinions. I wonder if the procedure in the jet age has been reviewed from operational historical data, and if it could be improved. Or has it been written in an office, tried in the sim and cast in stone forever?

Perhaps someone from ATC could contribute their opinions. They will be a major player in such a scenario. It will be interesting to know how they will react .