EasyJet A319 Complete Loss of Electric Power?
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As SLF, I am deeply troubled by the statement on page 27, paragraph 1.6.6.8, of the AAIB report.
"Loss of the AC BUS 1 and AC ESS busbars causes loss of both DC ESS and ACESS SHED busbars and thus prohibits the release of the passenger oxygen masks, either automatically or manually."
Perhaps some industry people can explain why Airbus and the certification authorities allow life-critical systems, in this case affecting 138 passengers, not to be fed by the same electrical network that was capable of feeding the co-pilot's displays and other key equipment? The AAIB report adds that the flight deck oxygen system is unaffected.
Cynically, the network redundancy appears to have been designed to get the hull and flight deck crew home.
"Loss of the AC BUS 1 and AC ESS busbars causes loss of both DC ESS and ACESS SHED busbars and thus prohibits the release of the passenger oxygen masks, either automatically or manually."
Perhaps some industry people can explain why Airbus and the certification authorities allow life-critical systems, in this case affecting 138 passengers, not to be fed by the same electrical network that was capable of feeding the co-pilot's displays and other key equipment? The AAIB report adds that the flight deck oxygen system is unaffected.
Cynically, the network redundancy appears to have been designed to get the hull and flight deck crew home.
Join Date: Aug 2005
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Cellphone & VHF
Almost right...max energy (and capture) is targeted at the clients, antennas being even, often, tilted towards the ground.
However, if one looks at a cell base station from a "certain" distance, it will reach a point where the observer will see the antenna at a 0° angle, making the link perfectly possible.
In other words, whatever the altitude of the observer (assuming he does not go stratospheric) he might be line-of-sight at an adequate (low) angle to get his cellphone working, especially if flying towards the cell base station.
(high relative speed > doppler effect when flying laterally to a base station)
VHF
Power output is largely irrelevant. Again, this is a LOS link, if it works with 25W it should work with 5 (even much less). The difference being the signal/noise ratio...obviously more power gives more "comfort".
However, if one looks at a cell base station from a "certain" distance, it will reach a point where the observer will see the antenna at a 0° angle, making the link perfectly possible.
In other words, whatever the altitude of the observer (assuming he does not go stratospheric) he might be line-of-sight at an adequate (low) angle to get his cellphone working, especially if flying towards the cell base station.
(high relative speed > doppler effect when flying laterally to a base station)
VHF
Power output is largely irrelevant. Again, this is a LOS link, if it works with 25W it should work with 5 (even much less). The difference being the signal/noise ratio...obviously more power gives more "comfort".
Join Date: Dec 2007
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@slf99: First, please consider the tone of your question. It implies a strong accusation while it appears to me you don't fully understand the design and the nature of the malfunction that happened in the discussed incident.
The passenger oxygen system is powered by the AC ESS SHED and DC ESS buses. By design, the essential buses (ESS) are meant for essential loads. So the passenger oxygen system is connected to the correct buses as per design.
Obviously the essential buses were unpowered in this incident. This should not have happened (and persisted).
The passenger oxygen system is powered by the AC ESS SHED and DC ESS buses. By design, the essential buses (ESS) are meant for essential loads. So the passenger oxygen system is connected to the correct buses as per design.
Obviously the essential buses were unpowered in this incident. This should not have happened (and persisted).
Join Date: Jun 2009
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Excuse me for coming into this at such a late stage, but I am going back on the Bus soon after a bit of a break so getting my head round some stuff again.
I`ve looked at the schematic and my moneys with Cat3 & Dan. Manually extending the RAT should restore AC Ess & DC Ess. However, when you decide to go away from the books / ECAM etc (on any aeroplane) the trick is really knowing what you want to achieve.
Sitting here at home it looks like an obvious option, but can someone elaborate on what help the ECAM and environment would have given them to conclude they had lost AC1 Ac Ess & DC Ess?
What I get so far is:
Loss of AC #1 = ECAM AC ESS BUS FAULT & DC ESS BUS FAULT procedure will lead to pushing AC ESS FEED P/B which should restore AC ESS Bus.It also says "ATC System 2"
DC ESS BUS FAULT says to use audio switching to #3.
So they still had neither ESS Bus ?
There is obviously loads of other stuff to deal with on this complex problem and it is always easy with hindsight. I never used to carry a copy of the ELEC Schematic but I will from now on. Sometimes it helps to get back to basics.
I`ve looked at the schematic and my moneys with Cat3 & Dan. Manually extending the RAT should restore AC Ess & DC Ess. However, when you decide to go away from the books / ECAM etc (on any aeroplane) the trick is really knowing what you want to achieve.
Sitting here at home it looks like an obvious option, but can someone elaborate on what help the ECAM and environment would have given them to conclude they had lost AC1 Ac Ess & DC Ess?
What I get so far is:
Loss of AC #1 = ECAM AC ESS BUS FAULT & DC ESS BUS FAULT procedure will lead to pushing AC ESS FEED P/B which should restore AC ESS Bus.It also says "ATC System 2"
DC ESS BUS FAULT says to use audio switching to #3.
So they still had neither ESS Bus ?
There is obviously loads of other stuff to deal with on this complex problem and it is always easy with hindsight. I never used to carry a copy of the ELEC Schematic but I will from now on. Sometimes it helps to get back to basics.
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Flyingstig
I am guessing from your queries you have not had the opportunity to read the AAIB report in full ? If not I would strongly recommend it as it will almost certainly answer all of your questions and give lots more detail as well, with several good diagrams to boot. See Aeroskid's post of 24th Aug.
I offer this suggestion in good faith as I am sure it will inform far bettr than many of the replies which you may get here. I found it very worthwhile.
SB
I offer this suggestion in good faith as I am sure it will inform far bettr than many of the replies which you may get here. I found it very worthwhile.
SB
Starbear
(as SLF) Thanks for that link: rather instructive - and concerning. Interesting to see how the recommendation to show switch position is received as this would seem to mean banning non-latching push buttons. Also the implied criticism of the certification diligence wrt this fault chain. All seems to have been handled very calmly considering, and a good steady report.
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Accident reports over history have made tons of 'recommendations' that never get implemented - smoke hoods for pax, rearward facing seats etc. Don't hold your breath for any major changes beyond those already underway.
Join Date: Jun 2009
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Starbear,
Thanks! Very interesting reading.
It alos gives a really good insight into the workings of the Elec system.
The guys did a good job, but its intersting to note that they thought about the RAT but did not persue the idea.
Also a salutory point made about being distracted from completing the ECAM!
Always a great help to learn from other`s experiences.
Yeah! Lets see how many `recommendations` are taken up , and how long the `requirements` actually take? Auto changeover of ESS Feed must be a priority, the fact that Airbus have seen fit to include it in later models rather gives the game away a bit!
Thanks! Very interesting reading.
It alos gives a really good insight into the workings of the Elec system.
The guys did a good job, but its intersting to note that they thought about the RAT but did not persue the idea.
Also a salutory point made about being distracted from completing the ECAM!
Always a great help to learn from other`s experiences.
Yeah! Lets see how many `recommendations` are taken up , and how long the `requirements` actually take? Auto changeover of ESS Feed must be a priority, the fact that Airbus have seen fit to include it in later models rather gives the game away a bit!
