That assumes they were aware of something seriously amiss that would warrant sending such a message. Although the descent was steeper than usual, (about 500-600 ft/nm?) it doesn't appear to have exactly been a screaming dive - and the onset appeared to be quite smooth.

(Caveat the above with the fact that I'm using the FR24 data which may contain inaccuracies)

Having had cause to don an oxy mask in anger in the distant past, I found that it could be done well within the oft-quoted TUC figures, even when taken by surprise.

Dear OLD BOEING DRIVER:

Your question was valid. The response by the one poster was horrid. It seems to be deleted by now. Another post by PORTVALE was polite and answered the question.

I would not expect someone who flys for one airline to know what is used at another airline. BUT I DO EXPECT REASONABLE QUESTIONS asked nicely to be answered and not shot down.

IF someone has flown 4 different types of jets, and not happened to fly an airbus 320 owned by germanwings, it is a fine question.

We have fleets of planes, some have FULL FACE MASK, others have oxygen masks and goggles. ( I prefer the masks and goggles).

IF one pilot left the flight deck for any reason and the OTHER pilot was not on oxygen and something happened, OOOPS, BAM.

It is easier to go on oxygen with just a mask. What are the european regulations about oxygen and one pilot leaving cockpit?

Sky high
 

Thanks for your response. We can all learn something from each other.

And, thanks to Portvale too.

Possible? Maybe... distraction / pre-occupation with an unrelated problem is not unheard of, and well documented (Everglades) - but one would think unlikely in this day and age - especially with modern bells 'n whistles.

But both pilots simply overcome by hypoxia so quickly also seems unlikely, on the face of it.

"In default of a timestamp, I should have looked at the latitude reading" @AirScotia - the 'mtime' column in that graphic is the time stamp (unix format seconds since 00:00:00 1st Jan 1970) converters are available online

Regarding the discourse on crew oxygen....My preflight oxygen system check was given more time and attention,after an experience,in Havana.
The crew oxygen had been changed,at European base,before previous transatlantic flight. The valve on the crew oxygen bottle,not accessible to crew in flight,had not been reopened!
Needless to say,had there been a decompression on the previous flight,the pilots would have been rendered unconscious...

Sky High
 

The reason behind my question about the full face masks was relating to pilot incapacitation due to smoke or fumes in the cockpit, causing eye irritation or temporary blindness.

They may have been on O2, but unable to see anything and trying to get to a lower altitude. Maybe pretty busy along that time, as well.

I think someone a few pages back touched on this concept

V/S Values
 

When looking at the V/S values derived from the FR24 data we will need to take into account that this data is not recorded in a way that allows to have accurate data to derive a precise sink rate from the recorded Mode-S data.


Neither the time stamps / intervals nor the resolution is up to that task. Therefore you can see a fluctuation on the V/S data that might not be there.


The track on the other hand clearly shows that the plane was on A/P.

skyhighfallguy,

No, not really, the engines on this A-320 are CFM56-5…

Having done the hyperbaric chamber training previously I have a few observations that we were told during the course.

Many are using the term "explosive decompression". We were advised that this term is incorrect; if you have had an explosion then that is a totally different problem. The term used is "rapid decompression" (note the title of the training video in post #224). This is defined as a total loss of pressure in less than approx. 14 seconds. The time used in the definition is based on the length of time it takes for oxygenated blood to circulate around the body and return to the lungs for replenishment with oxygen.

Secondly, most O2 masks are set by default to diluter demand. If the masks are donned in an unpressurised aircraft at FL380 they will not provide sufficient O2 for the crew as there is insufficient partial pressure to breathe. The mask must be switched to the emergency setting (unless A320 has a different system) to provide ram air O2 to enable breathing. If this was not known or done by the crew then the mask would be of little use.

While useful consciousness at FL380 is 12-14 seconds these figures are based on being aclimatised at that altitude. In a rapid decompression that time can be reduced to as little as 4-5 seconds due to the effects of numerous physiological effects such as 'The bends'.

Not speculating on the cause, just observations on others' speculation.

I was just wondering, for those that understand the A320, is there anyway a rapid decompression could prevent the aircraft's radios from working?

It is relevant since 100% O2 still will not supply the O2 at sufficient pressure to assist breathing. 'Normal' is a mix of O2 and cabin air, '100%' is all O2, 'EMER' is O2 forced out of the mask under pressure to inflate the lungs at high altitude.

It is not a matter of the percentage quantity of O2 being delivered. It is the fact that the lungs cannot inflate to inhale the O2 with the reduced partial pressure at that altitude. I've flown GIV for 10 years. It has the standard 'modern jet' crew mask.

Your comment highlights my point about the masks that was pointed out to us during the course; most pilots think 100% will prevent hypoxia at high altitude. It won't.

@daz211

ATC tried to contact them when they noticed the unauthorised altitude change... they didn't respond so an emergency was declared.

The pilots were likely unconscious and/or incapacitated by this stage...

"We have obtained copies of the contact between the control tower and the pilots of the plane. These show there was no contact with the plane after it started losing altitude and when the air traffic controllers tried to contact it there was no response."

http://www.theguardian.com/world/liv...s-live-updates

Freespeed2,

I've never heard of 100% being an issue for well executed emergency descent. If sustained unpressurezed flight at those levels, then yes 100% may not provide sufficient O2 for life.

You would hope that once you'd recognised the ECAM, donned mask, established comm, announced emergency descent, flicked the seatbelt sign on, and initiated the descent, the aircraft would be approaching the mid 20's within 2 1/2 mins and the 100% would have been enough to get you there without hypoxia setting in.

The primary function of the 'Emergency' setting as far as I know is for keeping the mask free of smoke. I'm certainly open to others opinions on this? Do I need to use 'Emergency' O2 at FL380???

@freespeed2, your comment regarding marginal O2 partial pressure at FL380 is entirely correct. I think the official limit is FL400 for positive pressure breathing apparatus requirements. However, the TUC comment isn't: the 12-15 seconds at FL380 is not for an "acclimatised" body. If it was acclimatised, decompression wouldn't be a problem... get it? ;-)

It rather depends on what it is you're doing (physical activity), and on your physical predisposition. Oddly enough whether you're fat or lean makes no difference, there are other factors at play, many not well known to aviation/mountaineering medicine.

The point is, 15 seconds is a very short time if you're caught by surprise, and there's no time to debug a problem if there is one, e.g. an insufficiently opened O2 bottle valve (not that pilots could do anything about that anyway), or flow regulators in the wrong position etc. You simply don't get a second chance.

What the flight path shows is consistent with the O2 bottle being shut off leaving enough O2 to initiate descent, then the pilots go incapacitated.

The high altitude chamber films show pilots recovering to a walking, talking state quickly after getting the mask back on - - after maybe half a minute without.

After several minutes of high altitude hypoxia, you will not suddenly regain your piloting ability when below 14,000.

Case in point: An Argentinian glider pilot woke up in a field with the glider missing the wing outer panels after being sucked up into a CB. He had no memory between the time he pulled the dive brakes and when he woke back up.

My O2 system will run down sharpish if I forget to open the bottle, but it will show up on the flowmeter before I get very high.

Before the quick donning masks, one pilot was required to be wearing a mask and breathing with it above 30,000 or so . A closed bottle would be quickly apparent and an RTB would be initiated if it could not be turned on in the air.

Today crews are betting their lives and those of the pax that mx has opened the bottle if there's a depressurisation.

Helios lost that bet and we may be looking at a repeat.

turbine d, thanks, cfm 56

old boeing...I understand exactly what you are getting at.


another poster, yaw string, indicated he checked his oxygen in havana after the inbound crew HAD NOT and found the valve OFF.

I've seen this too, esp after servicing. I am of the habit to make DARN SURE the oxygen system will work at 100 percent EMERGENCY and blow my lungs up and sound like the movie 2001 space odyssey .

this might have been part of the problem and I hope the oxygen service records will be released soon.

Fair point. Acclimatized is probably the wrong term. What I was trying (poorly) to explain is that the 12-14 seconds UC is a notional figure based on the circulatory period of O2 around the body. However the lecturers on the high altitude course were adamant that it is a lot less during rapid decompression. Nitrogen in the blood turns to a gas (the bends) which causes blockages of the blood supply thereby reducing the length of UC. They listed multiple other unpleasant physiological effects that are best not recounted here.

ED alt window setting
 

Just curious, are European pilots taught to know the MSA and to put it in the Alt window for an emergency descent? Or just spin and get it down?

While I agree the reported figures are subject to variation, in my experience, Mode-S V/S data varies not by the thousands, but hundreds in a steady climb or descent.

Possibly, considering the difficulties our guys apparently had in maintaining a steady ROD as per LR's suggestion:

Could have been the MCP mode they were in, VNAV or even HDG if the winds were constant through the descending layers. I know these are B terms, apologies if I'm not up on my Airbus autoflight vernacular.



I guess we can all make mistakes, but from an aircraft maintenance point of view, I've been told regularly that Lufthansa Technik is top notch.

I seriously doubt it. Too many cues to miss. Aside from the instruments - at very least they should have had the standby horizon and altimeter - there is an obvious attitude change, pressure changes along the way, and sound. Then again, with masks on, it could be missed if they were task saturated.

Nothing is impossible at this stage, but considering an 8 minute stable descent in daylight VMC, very, very unlikely. From what we know so far, crew incapacitation best fits the scenario.

I have not yet seen any discussion from bus pilots out there whether any possible scenario exists that could initiate a controlled descent from cruise while maintaining a constant heading without crew intervention ? (I would assume no...)

Bear in mind it could be one pilot at the controls with the other in or waiting for the bathroom. Just speculatin...

Rapid Decompression
 

AC 61-107A from the FAA has the most authoritative data I can find.

The table below indicates the time of useful consciousness from a rapid decompression at 40,000 ft is 7 to 10 seconds. If the pilots chose to initiate the descent before they donned their oxygen masks, it may have been too late.



TABLE 1-1. TIMES OF USEFUL CONSCIOUSNESS AT VARIOUS ALTITUDES

........................Standard Ascent Rate........After Rapid Decompression
Altitude (Feet).............Time..............................Time
18,000.................20 to 30 minutes............10 to 15 minutes
22,000.................10 minutes.....................5 minutes
25,000..................3 to 5 minutes...............1.5 to 3.5 minutes
28,000..................2.5 to 3 minutes............1.25 to 1.5 minutes
30,000..................1 to 2 minutes...............30 to 60 seconds
35,000..................30 to 60 seconds............15 to 30 seconds
40,000..................15 to 20 seconds............7 to 10 seconds
43,000..................9 to 12 seconds..............5 seconds

I do avionics design, which includes certification. All electronics must undergo a rapid decompression test. Equipment in the pressurized section of most airliners must be tested to (IIRC) 45,000 feet. A com is a critical item and must remain fully functional during and after the decompression test. Non-critical items such as IFE and galley equipment can stop working, but cannot create a safety issue (overheat, emit smoke/sparks, etc).

An actual production radio could have a defect and fail during a rapid decompression, but keep in mind there are at least 2 VHF coms. There are other ways to communicate a problem, but so far it seems these were never used. I don't have A32x knowledge but if the electrical system is typical of Transport category aircraft, there are multiple sources of power to the radios.

Some pilots carry a handheld com radio in their personal kit for true "belt and suspenders" redundancy.

As the Yanks would say, here's a 'primer' on how a Diluter/Demand oxygen system works.

As the name suggests it has two functions (and settings): Diluter and Demand.

Firstly the Diluter function. The switch has two settings: Normal and 100%.

In the Normal setting the system mixes O2 with cabin air to try and maintain the pressure of O2 in the lungs that equates to sea level (ie 'Dilutes' O2 with cabin air). As cabin altitude increase, the proportion of cabin air decreases until 34 000' where the mix is 100% O2 / 0% cabin air. As cabin altitude increases above 34 000' the mix remains 100% O2, but the pressure of O2 in the lungs decreases. At 40 000' the O2 pressure in the lungs is equivalent to an altitude of 10 000'. To remain conscious above a cabin altitude of 40 000' requires 100% O2 to be delivered under pressure - this is the realm of the Pressure/Demand systems fitted to fighter aircraft and not the Diluter/Demand systems fitted to commercial aircraft.

The 100% setting on the Diluter function will deliver 100% O2 at all altitudes. It's purpose is to be used when there is smoke / fumes in the cabin so that you do not breathe any contaminated air.

Now the Demand function. The switch has two settings: Normal and Emergency.

In the Normal setting gas will only flow into the mask when you inhale (ie 'On Demand').

The Emergency setting will deliver gas to the mask continuously under positive pressure. It also, is to be used when there is smoke/fumes in the cabin. The continuous flow of 100% O2 under positive pressure ensures that if there is a poor seal between the mask and the face, O2 leaks out and not contaminated air in. Whilst the Emergency Demand setting does deliver continuous gas under a small positive pressure, it is NOT a Pressure/Demand system. There is no requirement for one and is not it's design purpose.

News report, that the aircraft hit the ground with 700 km/h.

If that is true, it must be above the VNO at that altitude. I do not fly the Airbus, but I know, that it has overspeed protection, if it is operated normally (normal law or something).

I find it very weird and to rule out "deliberate act" at this point is too early - remember the Embraer in Namibia.

700 km/hr is 377 knots. At 6000 feet that would be about 335 Knots indicated. I don't know the Airbus, but the Boeing 737 Vmo is 340. I'm guessing the Airbus is similar.

350kias on the A320. So yes, very possible. And the high speed protection comes on a few knots past the VMO.

Question for Bus guys, when we check the crew oxy bottle pressure during the cockpit prep checklist, if the engineers had turned the oxy bottle off, would we still see pressure being indicated? Ie is the pressure sensor in the line or the bottle?

If we turn the overhead crew oxy rocker switch to off, that oxy indication goes Red or Amber by memory (different from the half boxed Amber presentation we often see). If oxy bottle was turned off but there was residual pressure in the line, we might still be able to carry out a positive oxy mask test and think all is well and if the sensor is in the bottle, the indicated pressure will also look good. Hopefully Air Bus have a safety feature to prevent this situation.

ukankedi

"There is an electronic list of instructions presented in a central panel (ECAM), telling the pilots what to do step by step"

Crew perform the Emergency Descent procedure by memory. ECAM actions are only called for when established in the descent.

Safety and quality depend on adhering to standards and procedures. There is a good reason why the LH group is respected on both, despite this sad event.

However I'm not sure ACARS data exist. The prime purpose of ACARS is to provide maintenance data so engineering may prepare to rectify a fault when the plane lands. This makes sense on longhaul flights, but makes little difference with stage lengths under 2 hours. As ACARS costs money to install and operate, its benefits must outweigh the costs. 4U works on the low cost model, I'd be very surprised if they would have ACARS. In the outfit I used to be with, we only had it for the longhaul fleet for above reason.

I recall that the quick donning oxygen masks which sit in those little boxes adjacent to crew positions came on the scene in the 1989s.

Before that the oxygen masks would be hanging from a hook and you would physically put them on and adjust the straps for good fit and actually breathe oxygen at 100% and NORMAL to check all was serviceable.

Also from time to time one would breathe oxygen usually to wake oneself up on arduous duties about ten minutes or so prior to too of descent. I also recall on the B707 that if a pilot left the flight deck for a comfort break it was mandatory for the other pilot to be breathing oxygen with mask fully fitted when above a certain Flight Level which I think was FL370.

With the modern systems crew don oxygen masks only when there is an emergency either in the simulator or the aircraft.

The practice of fitting the mask prior to every flight was a useful way to remind pilots about the importance of this vital life support system should the pressurisation fail and also gave extra confidence that the crew oxygen system was fully serviceable.

@ Wrist Watch
 

This is all very well in training but what of the likely realistic scenario where visibility in cockpit is zero, with loose items flying around and the wind noise is deafening because a side window has blown and the partial vacuum has wrecked your ears.

When asked what potential causes there could be, an Oz aviation specialist interviewed on Channel Seven TV Australia tonight says accident investigators will focus on the sensors and went on to detail the recent sensors issue with the A321.

He spoke of no other potential causes.

donpizmeov2 Airbus (and SOPs, for that matter) recommends one head always be up, flying the plane. It is actually one of the Airbus Golden Rules.

However, I understand what you mean. Even if you are PF, you wonder what is happening and keep looking at the system displays, especially during low workload periods, i.e. cruise. If the PNF is not communicating efficiently or keeping you in the loop you want to look inside even more (at least I do).

That being said, it is not the manufacturer procedures nor company SOPs at fault for loss of situational awareness, it is bad CRM practices and human curiosity.

@ Mickjoebill

Except that there is an OEB out to deal with just this particular scenario and has been drummed into every single Airbus pilot repeatedly for the last few months. In just such a situation the memory item is simply to switch off two ADR's. I find it highly unlikely that this crew were not aware of something so obvious.

Plus this in no way explains the lack of comms from the crew.

I don't know why a lot of people are so desperate to pin this on the AoA vanes and erroneous alpha prot activation. Perhaps it is the cause but, for the reason stated, plus the aircraft being in the cruise and outside any weather I'd be very surprised indeed.

When I trained with Lufthansa many years ago, the first check was,Oxygen and masks,-Checked one hundred. The flow was checked and the setting was one hundred percent O2

In an earlier post, I showed a table of Time of Useful Consciousness vs altitude.

Does anyone have an equivalent table of recovery times in a descent from altitude assuming a hypoxia induced loss of consciousness after a descent had been initiated?

I had the same thought. Just after TOC not an unreasonable time for one pilot to visit the toilet (especially if you'd meant to go on a busy turnaround but didn't). Just one pilot and cabin crew member in flight deck? (Well SOP in my airline anyway), rapid decompression and neither of the flight deck occupants get mask on in time. Other pilot incapacitated before gaining access to flight deck?