Ryanair Loss of Pressurisation 25th Aug

[cwatters]

I don't understand all the attacks on Hadow here. I heard him on the radio and at the time and I thought his comments were perfectly reasonable IF you accept he was making them based on his observations and while ignorant of all the facts.

On the report I heard he actually said something like..

"...a meaningful descent, I wont say plummet because..."

but as usual the media cut off the last part in most subsequent reports and inserted "plummet".

His reference to the oxygen masks not working is perfectly understandable. He clearly assumed (like many other people) that non-inflation means non-working. To sky he said..

".... From where I was sitting I could see about 20 masks and only a few of them were inflating..."

I suspect he feels a bit foolish now he knows how they work, but at the time he made them his comments were perfectly understandable.

[slip and turn]

ChrisKKB - it may 'seem to you' that the masks were working, but irrespective of any aviation technical knowledge skill or experience that you may have, you have absolutely no way of telling unless you know what kind of maximum cabin altitude the passengers were exposed to and how quickly it rose and fell again, do you?

And that is information that no-one has been willing to share, I assume because it is thought to be too commercially sensitive.


These oxygen generators are apparently frequently called "candles". That makes me think of roman candles and fireworks but I dont get too carried away with the notion.

However, reading a thread like this does lead me rather too easily to other articles like:
Expedition Technology News - Human Edge Tech , in which I can read things like:

In 1996, chemical oxygen caused the crash of a ValuJet DC-9 headed from Miami to Atlanta, Georgia. The plane's interior went on fire shortly after take off, and the plane crashed killing all aboard. Expired chemical oxygen generators were placed in the cargo compartment, without plastic caps covering the firing pins. Employees wrote the canisters were empty, when they were not.

In 1997, at the change of an air filter, one leaking solid oxygen canister went on fire for 14 minutes on the MIR station, spewing a torch-like jet of molten metal and sparks across the hab.

In March this year; an oxygen candle probably killed two British Navy sailors on a nuclear-powered submarine near the North Pole. Lucky enough, the explosion did not affect the ship's nuclear reactor. Part of the exercise was to measure ice thickness, which the Navy guys ended up doing in a big way: At the time of the accident, the submarine made an emergency surface straight through the ice cap.


What we seem to be left with, after a whole week of public wondering, is people on one side of the commercial equation saying things like 'Don't worry, it was nothing to worry about', and sober observers/reporters on the other side still asking obvious easy questions which remain unanswered.

If the airframe is flying again, the airline can damned well tell us exactly what was wrong with it, or the way it was operated last Monday. But self-evidently, they feel they are above all that.

[icarus sun]

The problem seems to be a lack of information. I would suggest an automated message is broadcast through the PA system whenever the masks drop,also if available a video on the tv screen at the same time. The passengers do not know anything about explosive decompression or about the mask system except a very brief "Brief" from cabin crew, and few pay any attention.

[SLF3b]

Just SLF, but the last safety briefing I heard said:

'Pull the mask over your mouth and nose and breath normally. Please note the bag does not inflate.'

Seems pretty clear to me. I think this is from a plane with cylinders, not chemical oxygen generators. How hard do you have to pull the lead for a chemical oxgen generator to work?

I am no fan of Ryanair, but if this had happened to BA it would not be news.

[llondel]

I am no fan of Ryanair, but if this had happened to BA it would not be news.

Had it been BA, the aircraft would have plummeted towards the earth, narrowly missing several schools and a hospital, while all the passengers screamed in terror and the pilot (note, only one) wrestled with the controls.

I think we need a smiley or icon to represent all of that, it'll save much typing in the future.

To be fair to TheAmbler, I thought the initial BBC report was well above the usual standard of media reporting of aircraft incidents.

[slip and turn]

"Please note the bag does not inflate"

is not a message I recall ever hearing as part of any Ryanair safety briefing this millennium, and I am not expecting to hear it any differently twice more this coming weekend.

But I did hear it here on PPRuNe, so thanks to the BBC for airing the matter so noticeably

For all I know, I could be in the same aircraft/same crew this weekend.

Currently all I have to reassure me is what I knew before Limoges (which was enough to keep me happy incidentally), and the new knowledge that if it happens again anytime soon then the airline is going to look either excrutiatingly inept or very unlucky

I suppose the downsides to that might be that crews might now unwittingly hesitate to drop the masks manually for a few weeks for fear of even bigger questions about what made it necessary in their case - I jest of course

[fireflybob]

I suppose the downsides to that might be that crews might now unwittingly hesitate to drop the masks manually for a few weeks for fear of even bigger questions about what made it necessary in their case - I jest of course

What are you inferring? That professional flight crew would allow their training and procedures to be dictated by the media? You must be living on another planet mate!

[slip and turn]

Well I did stick my non-alien tongue out, but you can infer what suits your purpose if you as a professional's professional are so disposed to look for inferences upon which you might take immediate umbridge, .... mate

[SLF3b]

I was on that plane, but there were three pilots and I didn't scream. Don't exagerate! I stand by my story - this is news primarily because it involved Ryanair.

Can anyone answer the question on how hard you need to pull the lead on a chemical oxygen generator to start the air supply?

[Jet Fuel Addict]

Back to the reason this all happened, I have heard from the CP that no-one knows (knew, this was a few days ago) what happened, that there wasn't any damage to the aircraft, that the plane wasn't misconfigured, and that the crew did everything in textbook fashion.

Fingers are pointing towards the software that regulates the pressurisation systems on the 738. Maybe the outflow valve was working on wrong information provided by the computers. The problem solved itself on a later stage in flight (at FL80) and numerous tests on the ground showed no faults at all.

Any clues as to what happened exactly would have to wait until Mr. Boeing comes back with the info available on the FDR and CVR. However as for the CVR I'm not sure how much info will be found on here as we recently got a memo stating
"Recent events have highlighted the requirement to pull the CVR circuitbraker once the plane is safely on the ground..."

PS, surprised to hear the airplane is back up flying...

[Crromwellman]

Ryanair Emergency

Seems to me that the crew acted professionally and promptly. The media went into their usual ill-informed feeding frenzy.

I was always taught that in the event of an emergency the paramount nmemonic was FTFA or Fly The F******* Aeroplane!! before indulging in secondary matters.

[doncas]

The reason that the CB for the CVR is pulled is because the data is recorded on a loop. By pulling the CVR CB you're saving all information for the previous 120 minutes. i.e. the CVR will not keep recording after you've landed the plane... The CVR keeps recording for 5 minutes after engine shut down.

In relation to the Cabin Pressure Controllers, and the Powered Outflow Valve, The operation of the CPCs is very dependable. One CPC is in control, whilst the other monitors, as a back-up. They then swap their roles after the flight. This prevents one CPC from being in control, and the other monitoring, all the time.

The powered outflow valve is simply a motor. It's job in life is to do what the CPCs tells it to. (In auto mode of course) and what you tell it to do (in Manual)

[ChrisLKKB]

Originally Posted by SLF3b

Seems pretty clear to me. I think this is from a plane with cylinders, not chemical oxygen generators. How hard do you have to pull the lead for a chemical oxgen generator to work?

From B/E Oxygen Systems :::Chemical Oxygen:::

Oxygen flow from the generators begins upon removal of a release pin from the flow initiation mechanism of each generator. This is accomplished by a lanyard which connects the mask or mask hose to the release pin. When a passenger takes hold of a mask, the lanyard will be at its full length. Bringing the mask to the face will remove the release pin and initiate the flow of oxygen from the generator. Since all masks connected to a single generator have lanyards attached to the common release pin, any of the masks are capable of removing the release pin and starting the flow of oxygen to all masks within that compartment.


To activate the oxygen generator you only have to remove the activation pin, this is done, (as the passenger briefings say), by pulling the mask towards you, this pulls on the lanyard which you can see in the photo which in turn pulls the pin out.

To anyone complaining about a lack of explanation on the opperation of the oxygen system in the passenger briefing, I don't see how you can elaborate on the instruction , pull the oxygen mask towards you without over complicating it and probably confusing people.

In short, if you are wearing the mask you have activated the unit unless of course you are 8 ft tall, in which case you probably will have been clouted on the head as the panel dropped down. None the less if someone next to you is wearing their mask then they will have pulled the pin anyway.

[Seat62K]

"Jet Fuel Addict",
I'm curious to know why you're "surprised to hear the airplane is back up flying". Please respond. Thanks.

[doncas]

Force required

The force required to start the flow of oxygen is minimal, you are not attempting to kick start the reaction by pulling the chord. You are merely allowing a firing pin to hit the ignitor cap...

Theory of operation:

By pulling the release pin the firing pin hits the
ignitor cap by means of a spring.

This ignitor cap activates the starter powder which
causes the chlorate core to produce oxygen.

The pressure in the housing increases due to the produced
oxygen.

Pressure pushes the membrane foil into a peak which
punctures the membrane foil and opens the release valve.

Oxygen flows through the outlet valve assembly to the
connector-line assembly.

[NSEU]

Can anyone answer the question on how hard you need to pull the lead on a chemical oxygen generator to start the air supply?

Think of the type of force you would require to switch on, say, a ceiling fan with a pull-cord. You could operate it with a thumb and a finger. To dislodge the pin from the firing mechanism, with the lanyard (thin white cord) taut, you only have to displace it by a centimeter (half inch), but if your eyes are full of dust, you might not be able to tell if the string is taut.

Pull on the mask cup, but don't worry about pulling too hard. The hose is quite long and you'd probably have to pull it down to your crotch to start putting any undue force on the hose (The hose also runs through a hole in a bracket which has a rubber grommet, which will offer a degree of resistance, so it would be quite difficult to pull the hose away from the oxygen generator).

[SLF3b]

So now I know. Thanks.

[Irishboy]

Originally Posted by Finbarr

This has been an incident waiting to happen for some time - on none of the safety briefings I listen to, including those from the "World's Finest" is it stressed that one must 'tug' the oxygen tube to start the chemical generators. "Pull the mask towards you" is simply not enoough.

The safety briefing on BMI doesn't mention anything about pulling or tugging the mask.

[rubik101]

There is no mention of tugging because, as has been pointed out oh so very many times, you merely need to pull ther mask towards you and place it over your mouth and nose.
If it is on your head, it has been activated.

Look at the picture...
See where the masks are?
About 14 to 18 inches above your head.
See the taut string with the pins in the unit?
Pull the mask around one inch from where it sits now and the pins will pull out.
Pins out, O2 produced.

End of story.

[slip and turn]

Originally Posted by doncas

By pulling the CVR CB you're saving all information for the previous 120 minutes.

Saving it until when? What's the difference between allowing the CVR to stop automatically after engine shutdown and pulling the circuit-breaker before engine shutdown?

Does automatic stopping of the CVR after engine shutdown also erase it?