Germanwings A320 Crash

JCX BXC

eatmyshorts wrote: »

6800 ft equals 7000ft corrected for the local Marseille QNH.
Therefore if 7000 was set in the altitude window, and the aircraft levelled off at that, it would be approx 6800 ft altitude.

The first thing in starting a rapid descent is to set a lower altitude in the FCU.

Can you explain that in layman's terms?

Irish Steve

To bring some specifics into this, the scenario that seems to be the closest fit to what's happened is a sudden dramatic loss of cabin pressure.

The factor that's significant is that at FL380, the time of useful consciousness for a fit crew is between 15 and 30 SECONDS, so the absolute critical thing in the event of a depressurisation is to get the Oxygen mask on before trying to do ANYTHING else, as if you don't, you may not be capable of doing anything else anyway.

The appearance of the profile is that the aircraft was put into a rapid descent but if for some reason the crew didn't get on to oxygen quickly enough, they may not have been able to complete the changes needed to make that descent safe. 6800 Ft is below the altitude that would normally be set for descent, 10,000 is normally regarded as being a safe level without supplementary oxygen, so that will be a significant investigation factor.

In the same vein, knowing that they were heading towards hostile terrain, a course reversal would have been appropriate, as that would have allowed descent to sea level without issues, but a change of transponder to 7700 before making that change would be the normal procedure.

The critical factor is that 15 to 30 seconds. You have to factor in the time for recognition of what's happened, if it was a sudden decompression, then there would have been some confusion over what happened, and that would have eaten into the very short time available. Pressurisation failure can't be fully practised in a simulator, as it's at (or relatively close to ) sea level, so there is not the hypoxia issues that will affect performance in the real event.

While it shouldn't have happened, there may have been some form of technical issue with the crew oxygen that meant it didn't work correctly, so they got their masks on, then started dealing with the issue, by starting an emergency descent, and were unable to carry on dealing with it because they didn't get the oxygen they would have needed to continue to function. If they passed out, then the aircraft would very happily have continued doing whatever they had set it up to do, the computers don't need oxygen.

The debris field is relatively small, so it would seem that the ground contact was what broke the airframe. Whatever happened was quick, in that it seems that there was no change in status (an emergency squawk, or Mayday radio call), but the level flight mode was changed in a stable way, as it seems to have been stable all the way down, which suggests a clear input from the flight crew.

The flight data recorder should reveal a lot of what happened in this scenario, as should the cockpit voice recorder, as it will have "supporting sounds" that will give the investigators a lot of background clues in terms of "noises" that are not related to conversation, but could be related to incidents or events on or close to the flight deck.

A word of caution, after the recent ATR incident in Taiwan, where information gathered from the FDR was released within a few days of the accident, it is very unusual for information gathered from a flight data recorder (or cockpit voice recorder) to be issued with any urgency, the in depth analysis of the FDR is normally not fully revealed until the final report, which could take several years to be produced, and the CVR data is not normally revealed at all. So, while there may be interim report(s), with some specific details, especially if there is an issue that affects all models of Airbus and requires changes by the manufacturer, or changes in procedure by the airlines, the specifics of this crash are unlikely to be fully revealed for some considerable time.

And NO, this is not a repeat of the AF447 type of incident, 447 was in a nose high stall all the way down, this flight was in a high speed stable controlled descent all the way down. The question that will have to be answered very urgently is was the crew still in control, or did they become passengers shortly after the incident started, with no further contribution made by them to the eventual tragic outcome.

Rayne Wooney

Would it not have been obvious to everyone on the plane that something was wrong? Assuming they were all conscious

Irish Steve

Carnacalla wrote: »

Can you explain that in layman's terms?

There is a window on the autopilot that the non flying pilot sets the altitude, or flight level that has been approved by Air traffic control, and the Pilot flying will then "accept" that setting, and activate it, and the aircraft then responds accordingly.

Air pressure varies on a minute by minute basis, depending on where you are on the face of the globe, and what the local weather is doing. To ensure that flights are correctly separated vertically, the standard procedure is that above a determined altitude, the sub scale setting of the altimeter is changed to use a "standard" pressure, and all flights operating above the transition level/altitude use this standard pressure, and as the actual height above the ground is not now involved, when using standard pressure, the height indicated is referred to as a flight level.


In the same vein, there is a pressure setting used for an area, (such as the Dublin area) which is the QNH pressure setting, which ensures that an aircraft operating anywhere in the Dublin Flight information region will have a minimum separation from terrain when operating using the QNH setting on the altimeter. It is (not a 100% accurate definition, but near enough) the sub scale setting that allows the altimeter to indicate the height of the aircraft above sea level. The altimeter sub scale is set to QNH when operating below the transition level, and is the setting used during the take off and landing phase of a flight.

And for what it's worth, the height indicated on sites such as Flightradar 24 are based on the Flight level system, so close to the ground, if the actual pressure is significantly different from the "standard" pressure (1013 Mb or HP), there will be a significant difference in the figure reported.

The only time the altiimeter shows the actual height above the (local) ground is if the aircraft is flying using the QFE pressure setting on the sub scale, which is the setting needed for the altimeter to indicate 0 when on the ground at the airfield where the setting relates to.

Hope that helps, it's a complex area of flight operations.

smurfjed

is it possible that the ILS locked onto some beacon in the alps/ outside the mountains?

Nope as range is only good for about 18 miles.

kub

Morning Ireland just got a report saying that the recovered black boxes are damaged

kippy

kub wrote: »

Morning Ireland just got a report saying that the recovered black boxes are damaged

This is the kinda stuff that annoys me again about 24 7 news. There always has to be some thing new about a story.
Of course they are damaged.....one would expect them to be. But it is much too early to determine if that damage will effect the data retrieval.

tharmor

Isn't the 2 year period to retrieve blackbox information too long ? They should be able to retrieve it quickly ?

Any ideas why it takes so long??

irishgeo

tharmor wrote: »

Isn't the 2 year period to retrieve blackbox information too long ? They should be able to retrieve it quickly ?

Any ideas why it takes so long??

On a plane that old its going to be a tape that tbe data is recording on. If the tape is physically damaged.it might need lots of work to get some data off.

RecordStraight

Mention of a door needing repair before takeoff on Morning Ireland there. Might lend some weight to the hypoxia argument.

cml387

Thanks to Irish Steve for one of the most sensible posts I've read in the entire thread.

Now more hearsay.
I heard something this morning about a problem with cargo door before the flight?

Red Alert

RecordStraight wrote: »

Mention of a door needing repair before takeoff on Morning Ireland there. Might lend some weight to the hypoxia argument.

Are the landing gear wells inside the pressurised envelope?

L1011

Red Alert wrote: »

Are the landing gear wells inside the pressurised envelope?

No. Hence why virtually all wheel well stowaways die

Aerohead

I know its probably a stupid thing to post but would there not be a case for allowing passengers to use mobile phones in flight, a lot including me would phone relatives if something serious was happening if you had the time , look at MH370 we could have learnt a lot if passengers were allowed to use phones as they could track the mobile phone signal and in this case it seems they would have had eight minutes to do so, it may have thrown some light on what was going on and help in some way to discover what happened.

Storm 10

Just came across this on the AV Herald website speculation I know but you never know

Structural failure
By Uknown on Wednesday, Mar 25th 2015 09:01Z


CVR data has been read. It seems structural failure (windshield? not determined yet)..It was quick... sound of cracks,but crew initiated emergency descent by autopilot and then they weren't heard anymore. Autopilot was on during whole descent, but disconnected automatically shortly before impact when GPWS alerts appeared.

philstar

why is it the white house that determines whether it was an act of terrorism?

what has the US government got to do with an internal flight in europe??

cnocbui

That matches my earlier speculation that the descent was initiated via the autopilot. If the there was a depressurisation incident and the cockpit oxygen system was inopperative, a crew member could have set the autopilot for an altitude below 10,000' or just to descend in the hope consciousness would be regained when a lower altitude had been reached.

unkel

Irish Steve wrote: »

the scenario that seems to be the closest fit to what's happened is a sudden dramatic loss of cabin pressure.

Agreed

Irish Steve wrote: »

The appearance of the profile is that the aircraft was put into a rapid descent but if for some reason the crew didn't get on to oxygen quickly enough

Again agreed, seems to be most reasonable explanation given what we have

Let's just hope somehow the oxygen for the passengers didn't work, although this is unlikely. Imagine passengers (on oxygen) knowing for the guts of 10 minutes that they are going to crash into the mountains and die

Irish Steve

Storm 10 wrote: »

Just came across this on the AV Herald website speculation I know but you never know

Structural failure
By Uknown on Wednesday, Mar 25th 2015 09:01Z


CVR data has been read. It seems structural failure (windshield? not determined yet)..It was quick... sound of cracks,but crew initiated emergency descent by autopilot and then they weren't heard anymore. Autopilot was on during whole descent, but disconnected automatically shortly before impact when GPWS alerts appeared.

The ONLY information I would give any credibility to on AV Herald is information posted by the site operator/owner in the main body of the site, as it will have been verified and validated by multiple credible sources. ANY other comments in the "thread" area are unmoderated, and not quality controlled, so cannot be trusted as being valid or appropriate.

That said, the scenario is unfortunately one that would be credible, and that may well eventually be validated as the reason for the accident.

kippy

tharmor wrote: »

Isn't the 2 year period to retrieve blackbox information too long ? They should be able to retrieve it quickly ?

Any ideas why it takes so long??

Have you ever tried retrieving data from a black box?
What is your reference point to make the assumption that they should be able to retrieve it quickly? What is "quickly"?
They may retrieve the data far faster, they may not, but the analysis of this data in the context of the overall investigation and completion of report MAY take two years to complete, it may not and there may or may not be preliminary reports in the meantime.

kippy

Aerohead wrote: »

I know its probably a stupid thing to post but would there not be a case for allowing passengers to use mobile phones in flight, a lot including me would phone relatives if something serious was happening if you had the time , look at MH370 we could have learnt a lot if passengers were allowed to use phones as they could track the mobile phone signal and in this case it seems they would have had eight minutes to do so, it may have thrown some light on what was going on and help in some way to discover what happened.

No,
This has been gone over a zillion times.

SpaceTime

Seems the latest from French authorities is that the cockpit voice recorder is damaged and attempts are being made to reconstruct it.

dodzy

wretcheddomain wrote: »

Aside from them - and only them - I won't be listening to any more hypothetical garbage, whether it comes from the 'experts' on Sky News or individuals on this forum.

B.S.

I love reading this forum. I'm always intrigued by the pilots on here that contribute regularly and I, for one, appreciate their input.

I find all the terminology fascinating and I think that their accrued experience and knowledge makes their analysis far more credible in terms of the events leading up to the disaster that some of the trash that I have seen on TV and in the rags.

Just reading Eatmyshorts reference to clearing the Himilayas by 5k ft regularly, it's just awesome. What a job.

PukkaStukka

Irish Steve wrote: »

The ONLY information I would give any credibility to on AV Herald is information posted by the site operator/owner in the main body of the site, as it will have been verified and validated by multiple credible sources. ANY other comments in the "thread" area are unmoderated, and not quality controlled, so cannot be trusted as being valid or appropriate.

That said, the scenario is unfortunately one that would be credible, and that may well eventually be validated as the reason for the accident.

To counter this, the following from RTE

RTE wrote:

No distress call was received before the plane crashed, but French authorities said one of the two "black box" flight recorders, the cockpit voice recorder, has been recovered from the site 2,000 metres above sea level.
"The black box has been damaged. We will have to put it back together in the next few hours to be able to get to the bottom of this tragedy," French Interior Minister Bernard Cazeneuve told RTL radio, adding the box was still viable.

This obviously casts doubt on a quick read of the black box giving the otherwise plausible windscreen scenario mentioned on AV.

Irish Steve

tharmor wrote: »

Isn't the 2 year period to retrieve blackbox information too long ? They should be able to retrieve it quickly ?

Any ideas why it takes so long??

Retrieving the information from the physical device can be done in a matter of hours, as was seen with the recent ATR accident in Teipei, providing the recording device is not damaged, which is the case with this accident. Even with damage to the devices, the specialists who deal with these devices are well experienced at recovering data from damaged devices.

Putting the correct interpretation on to the data from the FDR AND the CVR (and other external sources like ATC recording tapes) can take a very long time, as all the data sources have to be evaluated in parallel and in minute detail, often in slow motion, and the analysis may also require debris from the crash to be investigated in order to determine the sequence of events that occurred.

Bob24

philstar wrote: »

why is it the white house that determines whether it was an act of terrorism?

what has the US government got to do with an internal flight in europe??

The White House feel like they have to comment on this and give their insight and that is fine ... But they are by no mean the single source of truth and I don't think anyone is considering them as such.

sjb25

Aerohead wrote: »

I know its probably a stupid thing to post but would there not be a case for allowing passengers to use mobile phones in flight, a lot including me would phone relatives if something serious was happening if you had the time , look at MH370 we could have learnt a lot if passengers were allowed to use phones as they could track the mobile phone signal and in this case it seems they would have had eight minutes to do so, it may have thrown some light on what was going on and help in some way to discover what happened.

If you are unconscious you won't be phoning anybody

The flight recorders will tell everything that happened just won't be as quick as the media want

jmayo

I would like to thank Irish Steve whose measured response IMHO probably highlights the most likely cause of this accident.

Of course we may never know the exact minute detail, but eventually we should get pretty close.

The problem with todays media is that airtime needs to be filled.
Thus there is pressure from tv networks, news agencies, newspapers, web sites to find another fresh angle.

It doesn't matter if they have to talk to some guy directing traffic at the site or some politican looking to get their face on TV.

And the thing about the web is that it gives people who haven't a fecking clue what they are talking about the ability to spout their own theories.
Sadly sometimes these theories gain traction and take on a life of their own.

In todays world we want answers today, not tomorrow, so there is huge pressure put on authorities and organisations to quickly get to the bottom of accidents, incidents and catastrophes.
After a while a new story takes hold and that pressure lessons and even fades.

In this case there is pressue from airlines, aircraft manufacturer, governments and the public.
The investigators need time to do their jobs and they need to be as sure as humanly possible that they have reached the right conclusions, otherwise the correct lessons are not learnt and remedies are not put in place.

tharmor

kippy wrote:

Have you ever tried retrieving data from a black box? What is your reference point to make the assumption that they should be able to retrieve it quickly? What is "quickly"? They may retrieve the data far faster, they may not, but the analysis of this data in the context of the overall investigation and completion of report MAY take two years to complete, it may not and there may or may not be preliminary reports in the meantime.

All those are questions...dont get worked up mate !! I am not assuming anything but asking !!

tharmor

Irish Steve wrote:

Retrieving the information from the physical device can be done in a matter of hours, as was seen with the recent ATR accident in Teipei, providing the recording device is not damaged, which is the case with this accident. Even with damage to the devices, the specialists who deal with these devices are well experienced at recovering data from damaged devices.

Irish Steve wrote:

Putting the correct interpretation on to the data from the FDR AND the CVR (and other external sources like ATC recording tapes) can take a very long time, as all the data sources have to be evaluated in parallel and in minute detail, often in slow motion, and the analysis may also require debris from the crash to be investigated in order to determine the sequence of events that occurred.

Thanks thats what i was hoping to know....detailed answers....