Airbus Dual Eng Fail procedure question
Thanks for that graphic of the ELEC page on ECAM, sierra_mike.
Hi vilas,
Thanks for that succinct summary. I've just a couple of points.
In (2), as you say, each BAT is connected to its BAT bus (via its BCL) for charging and discharging.
In (6), could you clarify and expand on your last two sentences? I'm not completely sure what scenario you are addressing:
"Loss of generators is not a problem because APU GEN can power the AC buses. But without APU it is same as EMER ELEC without Emergency generator."
Hi vilas,
Thanks for that succinct summary. I've just a couple of points.
In (2), as you say, each BAT is connected to its BAT bus (via its BCL) for charging and discharging.
In (6), could you clarify and expand on your last two sentences? I'm not completely sure what scenario you are addressing:
"Loss of generators is not a problem because APU GEN can power the AC buses. But without APU it is same as EMER ELEC without Emergency generator."
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I am sorry thats a mistake. What I wanted to say was without generators and APU you will remain in EMER ELEC and Battery life is a back up for EMER GEN loss.
Last edited by vilas; 29th Oct 2013 at 14:57.
With reference to previous posts:
My understanding is that the yellow pump is not designed for continuous operation, (unlike the blue pump), and it will overheat after a few minutes. It's purpose is to assist retraction of the flaps in the event of low yellow hydraulic pressure. It's other uses are for on ground operations: to operate the cargo doors, recharge the parking brake accumulator (on some variants), and pressurise the hydraulics for engineering tests. But it is not designed as a full-time system.
The emergency electrical generator powered via the RAT and Blue hydraulics is of limited size, and therefore does not have enough spare capacity to keep the batteries charged as well.
Why are both these things limited? To save weight and cost. And also because a risk analysis has been applied.
rudderrat: You need hydraulics and an ELAC to control either aileron, (320/321). The right aileron is normally operated by ELAC1 controlling green pressure. If green hydraulics or ELAC1 fail, ELAC2 takes over, controlling Blue pressure.
Chris - your APU start explanation is spot on. A normal APU start is battery assisted, as you imply.
My understanding is that the yellow pump is not designed for continuous operation, (unlike the blue pump), and it will overheat after a few minutes. It's purpose is to assist retraction of the flaps in the event of low yellow hydraulic pressure. It's other uses are for on ground operations: to operate the cargo doors, recharge the parking brake accumulator (on some variants), and pressurise the hydraulics for engineering tests. But it is not designed as a full-time system.
The emergency electrical generator powered via the RAT and Blue hydraulics is of limited size, and therefore does not have enough spare capacity to keep the batteries charged as well.
Why are both these things limited? To save weight and cost. And also because a risk analysis has been applied.
rudderrat: You need hydraulics and an ELAC to control either aileron, (320/321). The right aileron is normally operated by ELAC1 controlling green pressure. If green hydraulics or ELAC1 fail, ELAC2 takes over, controlling Blue pressure.
Chris - your APU start explanation is spot on. A normal APU start is battery assisted, as you imply.
Last edited by Uplinker; 31st Oct 2013 at 09:58.
But anyway, guys, let's not get distracted here, the main thing is to be looking for an airfield and landing.
We've got no engines, remember?
We've got no engines, remember?
Last edited by Uplinker; 31st Oct 2013 at 09:49.
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Uplinker
If you loose G+Y due to low pressure ECAM will ask you to put yellow electric pump on with PTU OFF to recover Yellow hydraulics. It does not overheat.But Yellow electrical pump flow is only about 1/4 th of yellow EDP so cannot use PTU because it will cause again low pressure on both. Looking for landing field should have been after FLY in NAVIGATE part before application of the procedure.
If you loose G+Y due to low pressure ECAM will ask you to put yellow electric pump on with PTU OFF to recover Yellow hydraulics. It does not overheat.But Yellow electrical pump flow is only about 1/4 th of yellow EDP so cannot use PTU because it will cause again low pressure on both. Looking for landing field should have been after FLY in NAVIGATE part before application of the procedure.
Last edited by vilas; 31st Oct 2013 at 11:05.
Yellow AC pump (APU running)
Quote from Uplinker:
My understanding is that the yellow pump is not designed for continuous operation, (unlike the blue pump), and it will overheat after a few minutes. It's purpose is to assist retraction of the flaps in the event of low yellow hydraulic pressure. It's other uses are for on ground operations: to operate the cargo doors, recharge the parking brake accumulator (on some variants), and pressurise the hydraulics for engineering tests. But it is not designed as a full-time system.
And, in an afterthought:
But anyway, guys, let's not get distracted here, the main thing is to be looking for an airfield and landing.
We've got no engines, remember?
Yes, well remembered! Not much time for any overheat to take place. But, as you've suggested a serious issue re the general use of the Yellow AC Pump, it needs to be addressed, even though it may be off-topic.
Things could well have changed since I last flew the A320 in 2001, and I'm not an engineer. My understanding, however, was that the Yellow AC Pump is identical to the Blue AC Pump. In the event of the a/c being AOG with Blue AC Pump u/s, it's possible to rob the Yellow AC Pump and re-install it as the Blue Pump. (It may be necessary to rotate the pump manifold to a different angle for the fit. The resulting loss of redundancy in the Yellow system would be covered by the MMEL/MEL/DDM.)
Now it's worth remembering that the Blue AC Pump runs continuously during normal ops, being the normal source of Blue System pressure. So - if the two pumps are identical - overheating when installed in the Yellow bay seems unlikely.
Quote:
Chris - your APU start explanation is spot on. A normal APU start is battery assisted, as you imply.
Thanks, but - as I replied to TyroPicard - I guess it depends what he meant by "battery power". In effect, when available, the TRs do most of the work. There's no doubt that the BAT1 and BAT2 PBs must be selected ON for any APU start to function. But where the supply to the APU starter motor is physically taken from is unclear to me, and this is probably not the thread to discuss the matter.
My understanding is that the yellow pump is not designed for continuous operation, (unlike the blue pump), and it will overheat after a few minutes. It's purpose is to assist retraction of the flaps in the event of low yellow hydraulic pressure. It's other uses are for on ground operations: to operate the cargo doors, recharge the parking brake accumulator (on some variants), and pressurise the hydraulics for engineering tests. But it is not designed as a full-time system.
And, in an afterthought:
But anyway, guys, let's not get distracted here, the main thing is to be looking for an airfield and landing.
We've got no engines, remember?
Yes, well remembered! Not much time for any overheat to take place. But, as you've suggested a serious issue re the general use of the Yellow AC Pump, it needs to be addressed, even though it may be off-topic.
Things could well have changed since I last flew the A320 in 2001, and I'm not an engineer. My understanding, however, was that the Yellow AC Pump is identical to the Blue AC Pump. In the event of the a/c being AOG with Blue AC Pump u/s, it's possible to rob the Yellow AC Pump and re-install it as the Blue Pump. (It may be necessary to rotate the pump manifold to a different angle for the fit. The resulting loss of redundancy in the Yellow system would be covered by the MMEL/MEL/DDM.)
Now it's worth remembering that the Blue AC Pump runs continuously during normal ops, being the normal source of Blue System pressure. So - if the two pumps are identical - overheating when installed in the Yellow bay seems unlikely.
Quote:
Chris - your APU start explanation is spot on. A normal APU start is battery assisted, as you imply.
Thanks, but - as I replied to TyroPicard - I guess it depends what he meant by "battery power". In effect, when available, the TRs do most of the work. There's no doubt that the BAT1 and BAT2 PBs must be selected ON for any APU start to function. But where the supply to the APU starter motor is physically taken from is unclear to me, and this is probably not the thread to discuss the matter.
Last edited by Chris Scott; 31st Oct 2013 at 11:15. Reason: Title added.
Fair enough Vilas, I must have mis-remembered, and now you mention it Chris, I do remember something about pumps being interchangeable.
Perhaps it's the PTU that can overheat?
Perhaps it's the PTU that can overheat?
Last edited by Uplinker; 31st Oct 2013 at 17:54.
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PTU does not overheat but if PTU is not switched OFF when there is hydraulic Lo LVL then without load it overspeeds causing overheat of the other system leading to Dual Hyd failure. Thats why it needs to be switched of within two minutes in such conditions. Few incidents have happened when Green fluid leaked out when gear was retracted and being in inhibition phase the warning only came later at 1500ft. by then it caused overheat of Yellow system. Airbus has come out with a MOD that inhibits PTU during this phase.
PTU does not overheat but if PTU is not switched OFF when there is hydraulic Lo LVL then without load it overspeeds causing overheat of the other system leading to Dual Hyd failure. Thats why it needs to be switched of within two minutes in such conditions. Few incidents have happened when Green fluid leaked out when gear was retracted and being in inhibition phase the warning only came later at 1500ft. by then it caused overheat of Yellow system. Airbus has come out with a MOD that inhibits PTU during this phase.
Yep, that was it.
Cheers.
Cheers.
