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A320 dual engine failure scenario

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A320 dual engine failure scenario

Old 8th Dec 2016, 12:52
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A320 dual engine failure scenario

Hello dear colleagues,

Few days ago I saw the movie Sully which is quite good by the way, a scenario came in my mind and I would like to have your impressions about it, so here we are :


CAVOK weather departure from a 1800m Rwy, (no airport nor lake/river nearby), during climb out around 3500 ft dual eng fail due to birds strike (both damage no relight possible).

At that stage initially RAT will extend and you'll be elec emerg config with G+Y hyd system unusable.

Obviously the only option to avoid a forced landing is to go back on the opposite runway where you just took off, but according to QRH you need more than 2000m to land. Normal and alternate braking system are inop and you just have 7 applications on Yellow accumulators in order to land which is not enough.



Personally I was thinking about switching APU ON followed by Y elec pump ON which permit to recover Y HYD sys and upgrade your braking sys from accumulators pressure to alternate braking or may be even normal braking via PTU and drastically reduced the landing distance.


Would it work ? Is Y elec pump powerful enough to drive PTU ?

What would you do ?


Airbus QRH ENG DUAL FAILURE doesn't mention about switching ON Y elec pump, I think that's because the checklist consider only 2 options after a dual eng failure, force landing or ditching, airbus is not talking about a possible return on a runway from what I saw in the books.


I know that scenario is quite unlikely but I think it can be a good opportunity for us to go a bit deeper into the A320 systems.

I just hope that will not give bad ideas to a TRE reading this topic for a sim check !

Thanks for your help and happy landings
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Old 8th Dec 2016, 14:08
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Hi aurel90,

A rhetorical question? Or an old chestnut? It's 15 years since I flew an A320, and the only QRH I have to hand is even older than that. I'll try to stick to your precise scenario, which may not be typical. (You will, of course, have tried to restart both engines first.)

Sully might disagree that "obviously the only option to avoid a forced landing is to go back on the opposite runway where you just took off," and indeed it might not be practicable, for a variety of possible reasons.

My old QRH drill does not include any attempt to start the APU, although it does acknowledge the possibility that it might already be running for some reason (returning to base under MEL provisions with one ED (engine-driven) generator u/s, for example). However, my first comment on PPRuNe after hearing of the Hudson ditching was to opine that I hoped they'd started the APU, and that soon turned out to be the case. If it's available and there are no contra-indications to starting it, it's a no-brainer.

The reduction in battery endurance on the first failed APU-start attempt would nevertheless leave remaining battery endurance far greater than the endurance of the a/c, even if it happens in the cruise. IMHO, however, if the scenario begins at high altitude it might be worth considering delaying the first attempt until medium altitude in the glide, by which time the APU may have warmed up a bit. Failure of both engines is a completely different situation from a failure of all ED generators with one or both engines running, in which you might need (and be able) to fly on RAT and BAT for an hour or more.

There is a possibility, IIRC, that limited Green and Yellow hydraulic function may be available from windmilling engines in some cases.

With the APU running:
(1) all electrics are restored, including all ELACs, SECs and FACs;
(2) Yellow hydraulics can be restored with the Yellow AC pump, although Flaps will be slower than usual as the AC pump is less powerful than the #2 ED pump;
(3) Green hydraulics would be available via the PTU, but I can't comment on the advisability of using Green services. Someone else will comment. I imagine that it would still be advisable to use gravity extension for the L/G, which would also avoid any temptation to use the NW steering after landing? As for normal (Green) braking, similar considerations may apply, although the automatic transfer to Yellow brakes is, IIRC, swift.

Why would the 7 applications/releases of brakes you say are available from the Yellow brake accumulator not suffice for landing, even on a short runway?

Your choice of an 1800-metre runway for the return suggests that a slats-only landing would be challenging, so restoring Yellow hydraulics would be helpful, to say the least.

Last edited by Chris Scott; 8th Dec 2016 at 14:21. Reason: tidy-up
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Old 8th Dec 2016, 14:17
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Aurel 90
You raised very interesting topic which I had got clarified from airbus also. With dual engine flame out APU must be started anyway to get out of EMER ELEC. When Windmilling is insufficient then only you will get in G+Y fail and since hydraulic fluid is available ECAM will ask you to put on yellow electric pump that also gives you flap and reduces landing distance but it will ask to switch off PTU as the yellow electric pump fluid turn over is only 32 l/min as that of EDP which gives 140 l/mt. otherwise G+y will remain. Good thinking.
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Old 8th Dec 2016, 19:50
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Franky, in a scenario like that, runway length is not that much of a concern, I got bigger problems. Between landing off-airport and landing on airport with a not-long-enough runway, I'd still rather land at the airport. That's where the fire trucks are. If I get more hydraulics in the meantime - great, if not - I'm still heading for that runway.
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Old 9th Dec 2016, 01:09
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If landing on the runway is feasible, DO IT! Dribbling off the end at 30 knots is WAY BETTER than landing elsewhere!
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Old 9th Dec 2016, 01:38
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I suspect that with a dual engine failure at 3500 you would wind up like Sully did with one guy trying to get some power back and the other busy keeping it right side up and deciding where to point it.
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Old 9th Dec 2016, 01:50
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If you've flown directly away from the airport, at 3500' you are not going back there. If on downwind departure, maybe.
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Old 9th Dec 2016, 10:42
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Airbus very recently introduced a QRH procedure called the EMERGENCY LANDING - ALL ENGINES FAILURE procedure. The first step in the procedure is to Start the APU.
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Old 9th Dec 2016, 10:51
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Originally Posted by Chris Scott
Why would the 7 applications/releases of brakes you say are available from the Yellow brake accumulator not suffice for landing, even on a short runway?
Actually I just checked (QRH PER-32 Brake system NORM+ALTN FAULT A320 63T) you would just need 1690m to land in CONF FULL and 1950m in CONF 3, and as far I understand those distances are correct only if you have Flaps ! And in elec emerg config you only have Slats, unless windmilling is suffisant enough when you are configuring.

Originally Posted by vilas
the yellow electric pump fluid turn over is only 32 l/min as that of EDP which gives 140 l/mt
Thanks for the info, the difference between EDP and elec pump is much bigger than I thought, nice to keep it in mind. Is it written anywhere in our books or does it come from the answer by Airbus ?

Originally Posted by jack11111
If you've flown directly away from the airport, at 3500' you are not going back there. If on downwind departure, maybe.
http://www.ntsb.gov/investigations/A...ts/AAR1003.pdf

According to Hudson river's NTSB report you should be able to make it (not an easy task!), page 50 during simulator sessions some pilots managed to land on Rwy 22 starting the turn just after bird encounter at 2800 ft.

Originally Posted by dream747
Airbus very recently introduced a QRH procedure called the EMERGENCY LANDING - ALL ENGINES FAILURE procedure. The first step in the procedure is to Start the APU.
Thanks, my company hasn't updated QRH yet, but I'll keep a eye on it

Last edited by aurel90; 9th Dec 2016 at 11:34.
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Old 9th Dec 2016, 11:08
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Originally Posted by jack11111
If you've flown directly away from the airport, at 3500' you are not going back there..
Well yes, if you can't make the runway at all, worrying about going off the far end is a bit academic ...
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Old 9th Dec 2016, 11:35
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Quotes:
(1) "Frankly, in a scenario like that, runway length is not that much of a concern, I got bigger problems. Between landing off-airport and landing on airport with a not-long-enough runway, I'd still rather land at the airport. That's where the fire trucks are. If I get more hydraulics in the meantime - great, if not - I'm still heading for that runway."
(2) "If landing on the runway is feasible, DO IT! Dribbling off the end at 30 knots is WAY BETTER than landing elsewhere!"

Agreed! But, what are the chances of getting back there? And how much tailwind might there be for the approach and landing. (OP doesn't stipulate W/V.)

Quote:
"I suspect that with a dual engine failure at 3500 you would wind up like Sully did with one guy trying to get some power back and the other busy keeping it right side up and deciding where to point it."

Quite. Is this a moment for a snap decision by the PF, or is there still time for (rapid) DODAR to reduce the chance of a foul-up **?

Quote:
"If you've flown directly away from the airport, at 3500' you are not going back there. If on downwind departure, maybe."

Marginal, and easily screwed-up... Any retired Space-Shuttle pilots out there? If the a/c was over-performing prior to the failures, you might be closer to the upwind end of the departure runway than you realise? At 3500 ft you've probably already cleaned-up, so you're doing 210 - 250 knots.

At what point do you start turning back? Procedure-turn or a simple one-eighty? The latter would point you to a base-leg, of course, demanding an S-turn on to finals, amounting to a kind of retrospective procedure-turn anyway.

For a planned procedure turn, you might use the outbound segment to decelerate in level flight to, say 180 kts, extending the slats only (i.e., Flaps 1). That might take 45 seconds, and the precise timing would be unknown - yet crucial to the outcome. In that segment, not much height would be lost (if any). The 180-degree turn inbound would then take 60 seconds with 25-deg bank. How much height would be lost in that minute? Hopefully, the runway would then be in view, and that would be the moment of truth. It would immediately be apparent if you were too high or too low.

Quote:
"If you've flown directly away from the airport, at 3500' you are not going back there. If on downwind departure, maybe."

Marginal chance of success, I reckon. For it even to be theoretically possible probably depends on the wind and the pre-failure climb angle? And your choice has to consider what alternatives are available, if any.

Easy for me to stick my neck out...
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Old 9th Dec 2016, 12:52
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I think airlines should give advisory information about the height required in average winds for successful turn back or in case cross runways height required to land on the other one. It can be ascertained by Sim trials. Otherwise it will be very chancy guess work.
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Old 9th Dec 2016, 13:02
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aurel90
If you can reach any runway landing distance is not a problem because if you get APU Yellow electric will give flap also alternate brake with anti skid. Yes the fluid turn over info is from airbus.
Chris you will anyway have to wait for APU start because on ELEC EMER you cannot do above 250.
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Old 10th Dec 2016, 19:54
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With both engines stopped... You are now a glider !
I went to the French National Gliding at Montaigne Noire , to the east of Toulouse. Then it was a ridge site with the main strip along the ridge. Some of our flights used a short winch launch over the side of the ridge into the wind which was often followed by an immediate 180 degree turn, rather more than Rate !, to land up the slope (now with a tailwind). Use of the air brake or lift dumper generally got one to the starting point, ready for a further flight. These flights were timed by the Centre and were recorded as taking either 3 or 4 minutes. Their records listed that I made about a dozen flights in the day.
The turn was a tear-drop, not a proper procedure turn, which would have used up all my height. I do not think that this Centre is still open. I went there in 1951.

Early flying experements often the sides of hills. Some were made near Eynsford, south of Croydon. Engines were too heavy for the power output. Turns had to be gentle

Last edited by Linktrained; 10th Dec 2016 at 20:04. Reason: bits
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Old 12th Dec 2016, 00:05
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The gliders used in #14 were single or two seaters.

Much heavier gliders had been used AT NIGHT and WITHOUT LIGHTS to land, close to each other and their target on 6th June 1944 ( see Pegasus Bridge for more details).

If you really need an aeroplane for the comparison... Have a look at TACA110, an almost new B737-300 which HAD to be a glider and landed on the levee close to New Orleans on 14th. May 1988. Some days later it was flown away. It appears to have been retired, only quite recently in 2016, having worked a full life.
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Old 25th Apr 2017, 18:35
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Hello,

I wanted to know how much time would the pressure remain in yellow and green circuits after dual engine failure (due to wind milling)? When would we get a dual Y+G System failure?

Thanks!
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Old 25th Apr 2017, 19:50
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It is not the time but speed. At 3000ft. you will be in G+Y as the RPM drops and also because you will get your speed to GD and below. But from FL350 where you would be attempting wind milling relight at 300kts you will have hydraulics. But as you drop the speed to GD for starter assisted or below for approach you will loose G+Y. Sully didn't need APU nor was he in G+Y loss or EMER ELEC because he had engines.
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Old 25th Apr 2017, 21:30
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Originally Posted by Intruder
If landing on the runway is feasible, DO IT! Dribbling off the end at 30 knots is WAY BETTER than landing elsewhere!
Plus there are ways to shorten a landing :
- Use a lower speed than usual at touchdown
- Little flare (avoiding bounce)
- Sharp derotation or even braking as soon as you're well on the ground (nose landing gear up in the air, the brakes will slam it onto the runway but you've got worse to worry about)
- Max rev... Wait that will not work very effectively
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Old 26th Apr 2017, 01:57
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I can't emphasise enough how important it is to NOT start the APU should you find yourself with a dual engine flameout above FL250. I know that is not what is being discussed but I wonder if in the heat of battle the thought would likely come in to one's mind: after all that's what really helped Sully. (True enough)

PRO-LIM-49-20.

The reason I point this out apart from it being an Airbus limitation is that following a volcanic exercise in the sim some time back, I had a chance to try it afterward to determine if it was in fact a system inhibition logic that prevents it or a book limitation alone.

It was found, at least I the sim, that absolutely nothing will stop you from attempting to start the APU above FL250 but you will indeed cook the batteries and therefore be in a more trouble that Flash Gordon.

Airbus doesn't specify an altitude for the Sully procedure but please remember it is only for low level. That is all.
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Old 27th Apr 2017, 08:17
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Willie Nelson

APU didn't save the day for Sully because at no stage Sully had dual engine flame out. Both engines had RPM but not sufficient to sustain flight. It was just good airmanship to start the APU. At higher altitude you shouldn't be jumping the gun. Use the check list that would avoid busting limitations.
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