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Airbus A320 crashed in Southern France

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Airbus A320 crashed in Southern France

Old 25th Mar 2015, 05:25
  #421 (permalink)  
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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...)
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Old 25th Mar 2015, 05:31
  #422 (permalink)  
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Bear in mind it could be one pilot at the controls with the other in or waiting for the bathroom. Just speculatin...

Last edited by mcdude; 25th Mar 2015 at 05:33. Reason: typo
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Old 25th Mar 2015, 05:31
  #423 (permalink)  
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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.


........................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
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Old 25th Mar 2015, 05:58
  #424 (permalink)  
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I was just wondering, for those that understand the A320, is there anyway a rapid decompression could prevent the aircraft's radios from working?
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.
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Old 25th Mar 2015, 06:10
  #425 (permalink)  
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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.
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Old 25th Mar 2015, 06:13
  #426 (permalink)  
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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.
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Old 25th Mar 2015, 06:53
  #427 (permalink)  
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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).
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.
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Old 25th Mar 2015, 06:56
  #428 (permalink)  
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350kias on the A320. So yes, very possible. And the high speed protection comes on a few knots past the VMO.
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Old 25th Mar 2015, 07:01
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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.
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Old 25th Mar 2015, 07:13
  #430 (permalink)  
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"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.
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Old 25th Mar 2015, 07:32
  #431 (permalink)  
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...ACARS data has not been leaked yet!
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.
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Old 25th Mar 2015, 07:42
  #432 (permalink)  
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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.

Last edited by fireflybob; 25th Mar 2015 at 07:59.
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Old 25th Mar 2015, 07:46
  #433 (permalink)  
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@ 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.
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Old 25th Mar 2015, 07:49
  #434 (permalink)  
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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.
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Old 25th Mar 2015, 07:56
  #435 (permalink)  
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Well ... the majority of the airbus driver recognize the complexity of actions in emergency! possibly leading to loss of SA!
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.
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Old 25th Mar 2015, 07:58
  #436 (permalink)  
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@ 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.

Last edited by RexBanner; 25th Mar 2015 at 08:10.
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Old 25th Mar 2015, 08:08
  #437 (permalink)  
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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
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Old 25th Mar 2015, 08:11
  #438 (permalink)  
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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?
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Old 25th Mar 2015, 08:24
  #439 (permalink)  
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Bear in mind it could be one pilot at the controls with the other in or waiting for the bathroom. Just speculatin...
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?
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Old 25th Mar 2015, 08:43
  #440 (permalink)  
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Ok in an A320 there is pax oxygen system outlet in the toilet (drop down masks as in the cabin)and the cockpit door auto unlocks during during a decompression. So possible but not likely.
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