A320 dual engine failure scenario

[aurel90]

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 :ok:

[Chris Scott]

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.

[vilas]

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.

[Amadis of Gaul]

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.

[Intruder]

If landing on the runway is feasible, DO IT! Dribbling off the end at 30 knots is WAY BETTER than landing elsewhere!

[Rick777]

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.

[jack11111]

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

[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.

[aurel90]

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.

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 ?

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/AccidentReports/Reports/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.

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 :)

[DaveReidUK]

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 ...

[Chris Scott]

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... :O

[vilas]

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.

[vilas]

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.

[Linktrained]

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

[Linktrained]

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.

[AF330]

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!

[vilas]

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.

[KayPam]

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 :p

[Willie Nelson]

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.

[vilas]

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.

[Goldenrivett]

APU didn't save the day for Sully because at no stage Sully had dual engine flame out.

Hi vilas, The NTSB thinks it proved to be critical.

From ntsb.gov/investigations/AccidentReports/Reports/AAR1003.pdf (https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR1003.pdf)
page 104,
" Even though the engines did not experience a total loss of thrust, the Engine Dual Failure checklist was the most applicable checklist contained in the US Airways QRH, which was developed in accordance with the Airbus QRH, to address the accident event because it was the only checklist that contained guidance to follow if an engine restart was not possible and if a forced landing or ditching was anticipated (starting from 3,000 feet). However, according to postaccident interviews and CVR data, the flight crew did not complete the Engine Dual Failure checklist, which had 3 parts and was 3 pages long. Although the flight crewmembers were able to complete most of part 1 of the checklist, they were not able to start parts 2 and 3 of the checklist because of the airplane’s low altitude and the limited time available."

page 105,
"Although the flight crew was only able to complete about one-third of the Engine Dual Failure checklist, immediately after the bird strike, the captain did accomplish one critical item that the flight crew did not reach in the checklist: starting the APU. Starting the APU early in the accident sequence proved to be critical because it improved the outcome of the ditching by ensuring that electrical power was available to the airplane. Further, if the captain had not started the APU, the airplane would not have remained in normal law mode. This critical step would not have been completed if the flight crew had simply followed the order of the items in the checklist."

Each engine generator would have dropped off line when N2<55% or when the engine master switch is set to off. The windmilling engines would still develop some hydraulic pressure. See Page 55.

"FDR data indicated that both thrust levers were set to the idle position at 1528:01, about 50 seconds after the bird encounter. The N1 and N2 speeds for the left engine both decreased while the speeds for the right engine did not respond. About 30 seconds later, the right engine master switch was moved to the OFF position.95 According to the Airbus FCOM, for an automatic start sequence, when the engine master switch is in the OFF position and the throttle is set at idle, the fuel valve will only open when the N2 speed is more than 15 percent when in flight. When the first officer attempted to move the right engine master switch to the ON position, the N2 speed was less than 15 percent. At 1529:27, the left engine master switch was moved to the OFF position, at which time the N2 speed was about 83 percent. The left engine master switch was moved to the ON position about 10 seconds later, at which time the N2 speed was about 39 percent."

[vilas]

Hi Goldenrivett

For some reason I wasn't able to access the report. Thanks for the link.

[safetypee]

'What ifs' are to be encouraged, but their weakness is often the lack of context, or safety relevance (risk probability) and thus training value. There are also issues of simulation (training or PC), instructor knowledge, and use of the results.
If the OP question is a technicality, then that aspect can be discussed in isolation, however if it's within an hypothetical scenario then it is vital to consider the preceding events and the overall context of the situation.

The OP assumes that the failures have been clearly identified, without ambiguity, and with low stress; yet in many less severe real aircraft situations, crews suffered startle and surprise with degraded mental ability. With hindsight human activity can appear to be irrational, yet it probably made sense to the crew at the time. Thus it is very important to consider their viewpoint, not just our view in remote isolation from an ambiguous evolving event and very limited timescale.

The OP implied that the crew had sufficient mental model of the local area; this could be a gross assumption. More often the situation model has to be constructed - recognising and linking previous aspects, and only then might options and desired outcome be considered.

As per #4, fly the aircraft. Navigate to a suitable clear space; if this is a runway great, if not manage the approach as best possible to avoid obstacles. Stopping will be the least of your concerns.
Aim for normality where possible, don't think that you can make up procedures on the 'fly'. Aiming for a short low speed landing probably involves greater risk than an overrun.

Thinking for rationalising the situation and planning the outcome, and justifying the course of action will require whatever spare mental is available. The task is to avoid the crash, mitigate the outcome of a non ideal landing. At best we might be able to follow the advice in the checklist, at worst in attempting to rewrite the drills or consider low priority issues we may fail to achieve the primary safety aim.

PS. Crews may not have any more time that that taken to write and check this post; stopping, no more than the time to read the PS.

[vilas]

From airbus submission to NTSB from DFDR/CVR data. Despite suffering bird(s) ingestion in both engines, the engines did not suffer any uncontained failure but continued to deliver hydraulic and electrical power (engine N°1 N2 was high enough, up to the re-start attempt, for its IDG to remain on-line).

[Speedwinner]

Is anyone having a good rule of thumb how to fly the dual engine approach concerning which altitudes when and how to be configured?

[CVividasku]

If you've flown directly away from the airport, at 3500' you are not going back there. If on downwind departure, maybe.
I'm not so sure about that, however quick decision is key.
It also depends on speed at this altitude.

You do not need to perform a 360° (In total) turn. Actually a 180° and a bit more will be enough.
The optimal bank angle for that turn is 45° theoretically, but 37° would be more sensible given considerations about getting the correct speed (higher at 45° bank).

Given a 2000fpm rate of descent during the turn and 1700 after, at 37° the half turn should take a bit less than one minute, so you would end up at around 1500ft in front of the runway. Getting able to get there will depend on energy management, airplane performance during the climb, and wind.
Assuming no wind, an average of 10% (6° climb), you would be at 5-6nm at the beginning and end of the turn. At 3° descent rate you would be well aligned for the runway.

However it may be very difficult to guess at the first time when to get the gear and flaps out.
My guess would be flaps 1 as soon as possible, flaps 2 if landing is assured, or delay the flaps 2 if a bit low.
Gear down would be very difficult to time as well, because it may be the emergency gravity procedure. But my guess would be 30s before landing especially if a bit low on energy. Then, using F3/Full to convert speed into altitude if required. May also be used to reduce vertical descent.

Then, if flaring from 1700fpm, flare should begin at approx 100ft and at least 10-15kt higher than the VLS.
With the APU started it may be much easier to do (availability of hydraulics mainly, but also some computers)

Feasible, but on a complex aircraft like this I would be a bit worried about the likeliness of success..
On a light aircraft I've done this procedure without a problem in real conditions. The only problem is to convince the controller to do such an unconventional exercise.

The best option to manage such an approach would be to be very high on the profile. Use F1/gear down to aim for the runway an even speedbrakes if required. Being able to retract the speedbrakes gives the possibility to go back up on the descent profile.

Then, the most important thing about flaring the aircraft is to understand that for same flare intensity, if the vertical descent rate is x times higher, the flare height should be x^2 times higher. I use this technique successfully every time I perform a landing on a 4° slope. Flare height is almost double. Being this early also ensures more time to notice unsatisfactory flare and use higher than normal intensity if required. However for very large vertical speed differences, speed decay during flare becomes sensible and must be taken into account. Hence the 10-15kt which is a guess on my part for 1700fpm.
There is a physics computation that I did, for 1kt of speed trend at 150kt, you will have 75fpm. So to cancel 1700fpm, you will see a 22kt speed trend on the PFD. Flare will last for about 6 seconds so 13 kt lost. My guess was not too far off !

[hikoushi]

Is anyone having a good rule of thumb how to fly the dual engine approach concerning which altitudes when and how to be configured?

If you are trying this exercise in the simulator, a good way to feel out the profile is to start at 10000 feet or so directly above an airport, and spiral down. Have your PM run the long QRH (or ECAM if displayed) until too low (3000 feet? Your call). Then convert to the “Sully Procedure” on the back cover.

Profile wise, clean at green dot fly the circuit at about twice the height you would usually be for a given position. For example if you would typically be 1500 feet at 5 miles (300ft / nm), be at 3000 instead and so on. Save the configuration (at least beyond config 1) until you absolutely have it made, and start to feel just a little high. Give each configuration time to settle before selecting the next (you will need to lower the nose more than you think to maintain a safe speed as the drag builds up). The QRH gives a 1.5 : 1 glide ratio fully configured (A321). Give about 1000 feet to crank the gear down. If you are a little high on final, s-turns or whatever it takes to get down. Better a little high than a little low! Find your nonmoving aim point out the window. That does not lie.

[CVividasku]

The QRH gives a 1.5 : 1 glide ratio fully configured (A321)
Seems like a typo, what's the source of that ?
The actual glide ratio should be around 4 to 6.
​​​​​​​1.5 is worse than a parachute.

[vilas]

I'm not so sure about that, however quick decision is key.
It also depends on speed at this altitude.

You do not need to perform a 360° (In total) turn. Actually a 180° and a bit more will be enough.
The optimal bank angle for that turn is 45° theoretically, but 37° would be more sensible given considerations about getting the correct speed (higher at 45° bank).

Given a 2000fpm rate of descent during the turn and 1700 after, at 37° the half turn should take a bit less than one minute, so you would end up at around 1500ft in front of the runway. Getting able to get there will depend on energy management, airplane performance during the climb, and wind.
Assuming no wind, an average of 10% (6° climb), you would be at 5-6nm at the beginning and end of the turn. At 3° descent rate you would be well aligned for the runway.

However it may be very difficult to guess at the first time when to get the gear and flaps out.
My guess would be flaps 1 as soon as possible, flaps 2 if landing is assured, or delay the flaps 2 if a bit low.
Gear down would be very difficult to time as well, because it may be the emergency gravity procedure. But my guess would be 30s before landing especially if a bit low on energy. Then, using F3/Full to convert speed into altitude if required. May also be used to reduce vertical descent.

Then, if flaring from 1700fpm, flare should begin at approx 100ft and at least 10-15kt higher than the VLS.
With the APU started it may be much easier to do (availability of hydraulics mainly, but also some computers)

Feasible, but on a complex aircraft like this I would be a bit worried about the likeliness of success..
On a light aircraft I've done this procedure without a problem in real conditions. The only problem is to convince the controller to do such an unconventional exercise.

The best option to manage such an approach would be to be very high on the profile. Use F1/gear down to aim for the runway an even speedbrakes if required. Being able to retract the speedbrakes gives the possibility to go back up on the descent profile.

Then, the most important thing about flaring the aircraft is to understand that for same flare intensity, if the vertical descent rate is x times higher, the flare height should be x^2 times higher. I use this technique successfully every time I perform a landing on a 4° slope. Flare height is almost double. Being this early also ensures more time to notice unsatisfactory flare and use higher than normal intensity if required. However for very large vertical speed differences, speed decay during flare becomes sensible and must be taken into account. Hence the 10-15kt which is a guess on my part for 1700fpm.
There is a physics computation that I did, for 1kt of speed trend at 150kt, you will have 75fpm. So to cancel 1700fpm, you will see a 22kt speed trend on the PFD. Flare will last for about 6 seconds so 13 kt lost. My guess was not too far off !

Sorry! But failure at lower level is more of quick decision and visual judgment. Many things you assumed are not correct. APU won't give you hydraulics only Keep you out of ELEC EMER config. You will still be without G+Y hydraulic, in alternate law with only spoiler no.3 available so not much of help and with stab frozen. Approach speed is Weight+103kt and gear has to be by gravity atleast at 1000ft can be taken early but not late. That puts you in direct law so get Vapp before that. No Flap3 either as flaps at zero and slat 2&3 is same. Gliding distance will be height×2.

[safetypee]

"It heavily depends on the circumstances, i.e., when and where the dual failure occurred.

The situation will be very different if the engines quit during daylight, in good visibility conditions, at an altitude and distance such that the aircraft can glide to an airport and end up on a runway, or if they fail at low altitude in the middle of nowhere, amid mountains, above the sea, or above a large city.
So the final outcome will heavily depend on ‘providence,’ as well as on the pilots’ gliding skills and ability to make the right decisions."

" Lessons from the Hudson "

https://www.researchgate.net/profile/Jean-Paries/publication/291268264_Lessons_from_the_Hudson/links/60808ea0907dcf667bb5abf7/Lessons-from-the-Hudson.pdf?origin=publication_detail