Rapid decompression

[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

[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.