Rapid decompression

[raba9359]

Hello everybody, in my company there is some misunderstanding about commencing the emergency descend, some pilots are of the opinion that if we are cruising at 16000 feet and encounter rapid decompression then select open descend to reach 10000 feet whereas other pilots believe emergency descend is the correct procedure to reach to the legal height i.e 10000 feet

[RAT 5]

IMHO in this scenario we all know what the rules say, and there is only one set of rules i.e. one size fits all, but..........."rules can be for the obedience of fools and the guidance of wise men."
You are in a territory where obeying the rules can always be defended. Whether it was absolutely necessary or 'the best thing' to do is a discussion. However, you do not know how you employer or XAA will react to not following the rules 100% and may not sympathise with your airmanship decision to deviate.
Always a difficult one, as suggested in your question.

[deltahotel]

If I read you correctly you are asking 'for such a small descent, can we avoid doing the whole emergency descent palaver?' Which is a perfectly reasonably question. The follow on question is 'if you're not going to do it at 16000', at what level would you do it? - 17000, 18000, 24000?' Where would be your cutoff/ limit and why?

Rgds

[vilas]

It is possible that being drilled about rapid decompression you may resort to EMER DES but even if you didn't as long as the initial action of donning the mask quickly is done the rest is not important and shouldn't raise eyebrows whichever way you do. The difference in EMER DES from normal OP DES is donning mask, extending speed brakes and increasing speed to VMO. At 16000ft. time to useful consciousness is 25mts. and the descent to 10000ft(6000ft) in OP DES it will take less than 3mts. If you extend speed brakes and wind up speed to VMO ALT* should engage in a minute.

[RAT 5]

There has been an event where, due to screw up - naturally - the a/c ended up depressurised at FL130. The conditions were 'a/c was depressurised above 10,000' = emergency descent.' So they, in full robotic mode, did so. Discuss.

IMHO by the time all the pax had their O2 masks on etc. etc the a/c would have been at 10,000'. Also, by the time the crew did their memory items for Cabin Depressurisation, maintaining FL130, then thought about their screw up and then put an Emergency Descent into action, they could have been calmly at 10,000' or even realised their screw up and repressurised the a/c.

Not all situations are as Black & White as the QRH would have you believe. Sadly, genuine thinking is not encouraged, or even taught, until after the event the management scream at you "what were you thinking?. You did't have to blindly do the QRH."

[FlightDetent]

On my type the mask do not drop down automatically if not above FL140 cabin altitude. Part of the drill is to pres the MAN PAX OXY = ON, but then again only if CAB ALT is higher than FL140, for confirmation of the automatic deployment.

This value is chosen to satisfy regulatory requirements for PAX O2 supply.

Thread drift: do you use headsets with OXY mask on? In a recent SIM session I was advised not to do it, which surprised me to a great extent.

[Wageslave]

God help us, why can't you react appropriately to the situation you are in? Whatever happened to ^&*%$^&*(((!!!!!!

Oh sh!!t!!! I damn nearly said Airm*nsh!p!!!!!

What an utterly fatuous thread.

I thought this was the "Professional" pilot's rumour....etc????

[underfire]

wage, emergency descent vs open descent. its a valid question.

[Capt Scribble]

There will be little difference in time to 10,000ft from 16 and time of useful consciousness quite a while. Anyway, if the cabin reaches 14,000 before you get below, the masks will drop anyway. Over-reacting to emergencies can sometimes put you in a worse situation than you started off from!

[vilas]

Loss of pressurisation with damage doesn't give you any time to act appropriately. That is why it is one of the few memory items in airbus. Although FL160 is no issue really if you acted instinctively to do EMER DES you are slightly better off because of the use of speed brake which you may not use in OP DES. But this experience should not make you waste time if it happens at 350 or higher. Airbus recommends use of headset because there are no earphones with the O2 masks and noise levels may be too high for safe loudspeakers use.

[john_tullamarine]

Not giving an answer to the question in any way .. but, for side info, the certification standards require drop down masks for aircraft which cruise above F250. Below, things are a bit more step A, what did we miss ?, step B, step C and the descent can be a little more leisurely due to the better TOC .. not suggesting that one should dilly dally at all but there is rational time available, after going onto oxygen, to check for finger trouble and so forth.


Talking F160, I think, at levels in the mid-teens, one can invoke a little more deliberation than would be appropriate at F400 or so.


Keeping in mind that any emergency descent involves potential risks with other traffic.

[galaxy flyer]

Bear in mind, there have been cases, in the jet era, where bomb damage caused depressurization and the resultant emergency descent profile caused the fuselage to break up. a Vmo/Mmo descent is a stressful event for both the crew and the airframe.

The USAF story of a damaged C-141 comes to mind. It suffered a aft door failure damaging the tail and caused a near-explosive depressurization. The only pilot that remained conscious was a new LT in the right seat. He did nothing but reduce power and go down slowly at the current speed. Lockheed determined, as part of the investigation, that his (non) action saved everybody.

GF

[Peter G-W]

Vilas

What do mean exactly by saying that speed brake may not be used in Open Descent?

[vilas]

I meant OP DES/DES is normally done without speed brakes(not forbidden) while in EMER DES we use speed brakes.

[Amadis of Gaul]

Vilas, out of curiosity, what mode do you "normally" use speed brakes in, besides EMER DES (which is not a mode, but that's beside the point)?

[vilas]

What I said was in connection with the original question to highlight how little the two suggested options differ. In EMER DES use of speed brake is a rule and in OP DES it is an exception, as required basis. I don't need to tell you when to use them?

[Amadis of Gaul]

What I said was in connection with the original question to highlight how little the two suggested options differ. In EMER DES use of speed brake is a rule and in OP DES it is an exception, as required basis. I don't need to tell you when to use them?

I see you edited your original post.

[Airmann]

On another note:. Selecting where to point the nose when starting the descent is actually something one should think about carefully. The way I was taught its spin and pull, spin and pull, pull. Don't think just do.

But how much to spin the heading, and in which direction? I was flying along one day when I realised that if we were to turn left and start a descent we would fly straight into reciprocal traffic on an adjacent airway. It's not always so black and white. Shame they don't teach this procedure in more nuanced way.

[RAT 5]

I was taught its spin and pull, spin and pull, pull. Don't think just do.

When I first started reading this, after the sentence about pointing the nose and descent, I had scary imaginations of someone in a jet cockpit using lots of rudder and lots of back elevator and then experiencing lots of g. Silly boy. But I don't understand the 'pull' bit.
The direction of the HDG change is indeed something to consider. I used to teach the F/O, as PM, to beware of the captains who will always turn left. So there you are flying east along the Turkish coast with high MSA on the left and low level sea on the right. Hm? Beware.

[Escape Path]

RAT, he's talking Airbus language. The pull bit is to activate the selected modes for descent, heading, and maintain speed (initially). Equivalent to getting out of VNAV/LNAV in other aircraft.

Airmann, I guess you're right on that "just turn-pull, don't think" bit. After all the main idea is getting the aircraft on the descent ASAP. You are supposed to refine your targets to a meaningful value on the "second loop".

The where to point the aircraft is a good judgement call, I reckon. Does that heading takes me to the closest suitable airport? Is the terrain high or low on that side? Was there traffic info on the side I'm turning?

We do take terrain into consideration in quite a high priority as we fly in a country with three very high mountain ranges (where the Andes end, mind you), so it makes it our first consideration as we will certainly end in a zone where the MORA is over 10000'

[vilas]

Location of high terrain and airways on one side of the track as compared to the other should form part of the situational awareness as we go along the route. When rapid decompression happens at usual cruise altitudes of around 350, due to the time constraint we just do what is already considered. Presence of nearest suitable airport cannot be thought of at that moment nor there is any need for that ,because even if you land up some distance further up it is not going to make any difference. That will form part of the situational decision/Diversion once you have safely levelled out and taken care of other things. What is taught in the SIM is how to execute the manoeuvre swiftly. Commencing descent, initiating turn and freezing Mach in the first loop and refining those targets in the Second loop. However the very fact you commence descent without prior ATC clearance exposes you to some risk with other traffic but cannot be helped. Real life refreshers in TCAS for others.

[Airmann]

Firstly, apologies it seems that so many people on this forum fly Airbus that I forgot to even mention that.

Secondly, sure my company has specific escape routes when we fly over mountainous terrain. I am talking generally about non mountainous terrain.

I actually did some calculations and here is what I worked out. The closest any two airways are spaced in almost any part of the world is 10NM from centre line to centre line (am I right here? Or is it 20?). At a ground speed of approximately 500kts if one were to turn 45 degrees left or right one would have to cover approximately 14 NM in a straight line before intersecting the next airway and this works out to around 1 minute and 40 seconds. So if you were to descend at 6000fpm you would lose approximately 10000ft. The emergency descent would take no more than 5 seconds to initiate so that leaves you with 1 minute and 35 seconds to judge distances and decide where to navigate.

[sonicbum]

Hi Airmann,

I actually did some calculations and here is what I worked out. The closest any two airways are spaced in almost any part of the world is 10NM from centre line to centre line (am I right here? Or is it 20?). At a ground speed of approximately 500kts if one were to turn 45 degrees left or right one would have to cover approximately 14 NM in a straight line before intersecting the next airway and this works out to around 1 minute and 40 seconds. So if you were to descend at 6000fpm you would lose approximately 10000ft. The emergency descent would take no more than 5 seconds to initiate so that leaves you with 1 minute and 35 seconds to judge distances and decide where to navigate.


It is all very theoretical as airplanes may be flying directs to or be on specific heading/offset to avoid weather for example. As vilas stated before it is all a matter of situational awareness and being familiar with regional procedures in case of decompression for instance.
Always make sure that, according to the area that you are overflying, you know what the regional procedure states should you require an immediate descent without obtaining a prior ATC clearance which will be the case in a rapid decompression.

[sonicbum]

Hello everybody, in my company there is some misunderstanding about commencing the emergency descend, some pilots are of the opinion that if we are cruising at 16000 feet and encounter rapid decompression then select open descend to reach 10000 feet whereas other pilots believe emergency descend is the correct procedure to reach to the legal height i.e 10000 feet


Hi,

as you are probably referring to Airbus according to the terminology you have used, it is mentioned in the FCTM that an emergency descent is required if you experience a sudden uncontrollable and excessive cabin altitude. In other words if you estimate that you can reach 10'000 ft before the cabin altitude does then you don't have to apply the emergency descent procedure, that would be the case of a slow decompression (door leakage, loss of Packs, Bleeds) with the airplane flying at relatively low cruising FL as in your example.

[RAT 5]

In other words if you estimate that you can reach 10'000 ft before the cabin altitude does then you don't have to apply the emergency descent procedure, that would be the case of a slow decompression (door leakage, loss of Packs, Bleeds) with the airplane flying at relatively low cruising FL as in your example.

Ah, a thinking pilot. I've discussed this scenario with many views under training using the 'what if' format. I was amazed how many just went for the one size fits all full on ED. When this other airmanship option was discussed there were wide eyes and "are we allowed to do that?"

[sonicbum]

Ah, a thinking pilot. I've discussed this scenario with many views under training using the 'what if' format. I was amazed how many just went for the one size fits all full on ED. When this other airmanship option was discussed there were wide eyes and "are we allowed to do that?"


Ehehe unfortunately nowadays some terminology such as "airmanship" and "sound judgement" seems to be gone out of the window and everything is left to "let's just apply the procedure". Nowadays with the implementation of the Evidence Based Training we are trying to have back thinking pilots at the controls as history shows that failures and situations in general rarely develop in the way we have learned them in the SIM and a good understanding of "what is going on" is paramount to be safe rather than just sticking to some kind of "there must be a procedure somewhere".
Just my 2 "off topic" cents :8

[RAT 5]

Sonicbum: I agree. I was once told by a trainer that the strength of following SOP's was a defence if it went wrong. Sad times, but perhaps true. In older days the responsibility of the crew, and expected by my CP, was to do the best appropriate to the situation. Crew discretion to use airmanship. That attitude is not trained nor encouraged. And then.....you end up in a situation not forecast by the SOP guru's and the crew freeze or worse, panic. The management & investigators wonder why they didn't use airmanship; and then blame pilot error. Oh dear.
You can't expect a captain of 4 years on line to have the experience of a 7 year F/O pilot. You can't expect a 1-2 year cadet to have the experience of a 4 year F/O pilot. Now you combine the two??? and add in a non-QRH subtle malfunction, or even severe weather. Is there a crew or the blind leading the blind?

[sonicbum]

You can't expect a captain of 4 years on line to have the experience of a 7 year F/O pilot. You can't expect a 1-2 year cadet to have the experience of a 4 year F/O pilot. Now you combine the two??? and add in a non-QRH subtle malfunction, or even severe weather. Is there a crew or the blind leading the blind?


That's how things are done nowadays apparently. First flight on a SEP a/c, no or maybe 1 solo, hours & hours of FFS and about 4 years later first flight on the LHS of a 73/320.