Pressurisation incident Rome-LHR

[Porker964]

A mate of mine (very very frequent SLF) was on BA0559 (I think) out of Fiumicino bound for LHR when they turned back due to "pressurisation problems".

Oxygen masks popped out, cabin crew looked a little worried, but all in hand so back to the Telegraph crossword.

Sometime later there was a call from the Captain for the CSD to make his way immediately to the flight deck delivered in a "buttock clenched" tone of voice.

Apparently "very aggressive" approach and safe landing to audience of full emergency services.

All handled very professionally, and no criticism anywhere - but a question from my chum - who flies almost daily but is only a highly intelligent, educated banker:

What could have caused such an event? His assumption from the urgency and seriousness of the whole situation was that there was a "hole in the 'plane". Surely not...

[JW411]

Actually, cabin pressure is indeed controlled by "holes in the plane". They are called discharge valves or outflow valves. In very basic terms, the amount of air coming into the cabin from the engine bleeds is constant. The cabin pressure is controlled by adjusting the outflow by means of the discharge valves. These are open on the ground and closed at altitude.

Discharge valves on most aircraft are controlled automatically and can also be controlled manually. Loss of control of a discharge valve could result in the cabin altitude climbing to such a height that the drop down oxygen mask system operates.

Another possible cause could be an air-conditioning pack problem. The packs condition the air drawn from the engine bleeds (in terms of temperature etc) and delivered to the cabin. It is not that uncommon to have to shut down a pack which, for example, might be tending to overheat. This in turn could possibly lead to an increase in cabin altitude.

[jungly]

Most companies have the same procedures to be extra safe.

The pilots will put their masks on immediately...even if it is only a slow depress (just in case it becomes an explosive depress)....and their masks will stay on until below 10,000ft.

During this period, whilst completing checklists, ECAM actions and organising a return - there is little to no communication with the Cabin Crew. (The CC should be in a seat with masks on too!)

Once below 10,000.....it is really important to get the CSD to the flight deck. He/she may have some useful info about what has caused the depress. The CSD will also advise on any problems with the passengers (a depress can be quite uncomfortable....and lastly the skipper can tell the CSD what has happened and what the plan is. (without using the PA and scaring all the SLF to death.)

The "buttock clenched" tone is probably 1. symptomatic of the high workload the Capt is under and 2. the SLF being 'extra sensitive' to the skippers tone. Ditto the 'aggresive approach'

(Its funny how many pax suddenly hear strange noises, just as you cross the coast!)

I hope this makes you friend feel better........ its sounds to me like it was handled very well by the crew.

[Capt H Peacock]

I suggest that the Captain's tone may have been due to his/her wearing of an oxygen mask. In any pressurisation incident, the flight crew would go onto oxygen as a sensible precaution if nothing else.

It is quite rare to lose all pressurisation in an aircraft, it may possibly have been due to loss of control of the outflow valve. Such incidents have happened in the past because mobile phones on board have interfered with the valve controllers. Like many other systems in the aircraft, they contain sophisticated electronics which are intolerant to the sometimes powerful emissions from mobiles, especially in the acquisition phase.

Such a cause would not surprise me, it's amazing how many passengers still refuse to turn them off!!:*

[woodpecker]

What type of A/C was it.

Why I ask is that I had an emergency descent when we lost control of the discharge valve on a B757.

The system had two automatic controllers and one manual overide, but if the valve itself fails (jamed) then there is not a lot you can do...apart from getting down to some thick air...quickly

[Porker964]

I'm not sure what was being operated I'm afraid.

Thanks everyone for great responses - clears a lot up.

And yes, it sounds as though the whole crew did a very good job in a no doubt difficult situation.