Virtual A320 Triple Hydraulic failure
 

Hi all.
Yesterday during a 5 hrs leg i was discussing with my cpt about it.
What in case of a triple idraulic failure?

Airbus doesn't even consider it and ok, it's pretty impossible for it to happen but.......just for training what would you think will happen?

A. Sure death

B. Just with rudder and Diff. Thrust. what would happen to the trim which is mechanically connected but inoperative with absolute loss of Hyd power?

I said that it would be probably death, but in case of a non abnormal trim position maybe, with God's assistance something would have been possible to do.

let me know what do you think about.

cheers and merry Xmas to all.

GJ.

Aaaah, a triple Hydraulic failure, OK.

Well unlikely in the extreme, with leak isolation valves. Anyhow, try asking the TRI/E next time in the sim for this scenario, after all the boxes are ticked. It can be done, but is VERY hard work, even with 1 doing thr/levers, the other the rudder. If you had a tad of x-wind, nah, find somewhere else to land if possible.

EGGW

Eerrm.... what rudder?

Perhaps there have been some modifications lately, but all 319/20 in our fleet have hydraulically operated rudder. It can be mechanically signalled in case of total electric loss, but there has to be at least one hyd sys alive. It might be yellow or green via eng pumps or blue via RAT but you definitively need hydro pressure to move it.

So was there a change in the flt ctl architecture or did I miss something?

There have been plenty of DUAL HYD SYS LOSS (G/Y).

It's only a matter of time until a tripple happens.....

This is what i was in doubt of.
as far as i know in the "mechanical backup" the rudder is still operative but i was also told that it's the only surface still connected mechanically and it should work in any case even in a complete hyd loss scenario.
if it's not like that i now have the answer as it's a sure death.

cheers

different frame but did someone say sioux city

http://en.wikipedia.org/wiki/United_Airlines_Flight_232

I checked it on Fcom and even the rudder is operated hydraulically than with the 3 sys inop even the rudder is gone.

gj

The term mechanical back up refers to the loss of all flight control computers which would leave you with Stab Trim, Rudder & thrust control (symetrical giving some additional pitch control & asymetric giving additional yaw control).

With no hydraulics you only have thrust control.

As to the question of rudder control try moving the rudder while shut down on the ground. Now add the aerodymamic forces at anywhere from 0 - 350 kts :confused:

It should be possible to get near a runway, I seem to remember a certain DHL A-300 landing in Iraq with a total hydraulic loss.
I have had a go in the sim with a triple system loss and it was surprisingly controllable, but we didnt have an attempt in landing....

And do you really think the Sim is accurately modelled with no Hydraulics :{ In fact, do you think it has been modelled at all, and if so, how ;)
NoD

From a B707 manual

"Failure of more that two TRU is so unlikely that it is not even considered here"

So what a wing could fall off.
A control cable could snap.

Give me a new QRH

Well I don't suppose it is but it does represent a reasonably accurate aerodynamic model of the aircraft and I suspect that the way it behaves with the hydraulics switched off is not a million miles away from how the aircraft would behave under similar circumstances. I have had a go in a 320 sim and although you can fly it around the sky on engine thrust fairly easily it becomes pretty much impossible once you try to maneuver for an approach and landing. My admiration for the the two (that I know of) crews that have pulled it off for real is immense. Not just an Airbus problem of course, every Boeing from 747 onwards has needed hydraulic power to move the surfaces, the 737 was last one with manual reversion.

Virtual
 

Well in a virtual state, anything can happen.

But in the REAL world, loose all 3 hydraulics and unless your chuck yeager with the throttles, your DEAD.

It's as easy as that, and has been on all airbus aircraft. some have defied logic such as the A300 in baghdad but it takes a great amount of skill to land the aircraft under these circumstances.

Apparently if it happens - in any aircraft - the recommendation is to extend the gear as soon as possible. The rationale is that this assists in damping the inevitable phugoid motion from using thrust to control pitch.

There have been studies done (NASA?) with a view to someday include a "thrust only" reversion into future flight control software.

http://dtrs.dfrc.nasa.gov/archive/00.../01/TM4320.pdf

http://dtrs.dfrc.nasa.gov/archive/00.../01/TM4324.pdf

:ok:

Quote:
And do you really think the Sim is accurately modelled with no Hydraulics :{ In fact, do you think it has been modelled at all, and if so, how ;)
NoD

NOD
I forgot to mention it wasn't a microsoft flight sim!!
I gather that modern simulators are considered to be training tools, so I would assume that a no hydrauic flight has been modelled, otherwise we wouldn't have been able to do so...
We didn't attempt a landing because I think crashing an airplane in the sim is considered negative training! :eek:

If the SIM is "lost" with 3 HYD SYS LOSS, giv'm a try without touching the controls.

Try to fly it just by thrust/asy-thrust.

Nope, sorry. Modern full flight simulators are indeed training tools, and as such are intended to enable teaching of the various approved or recommended procedures, normal, abnormal and emergency.

If it's not in the flight manual, there is no expectation you'll be trained on it, and therefore no-one's going to waste time fine tuning the sim for a case that "doesn't exist".

The sim may also not be tuned for various combinations of failures; it may be representative, or it may not, depending on whether the failures interact in interesting ways or not. There's a set of generic validation tests for a sim, and there may be additional ones based on a specific training regime, but anything outside of that is rather nebulous.

MFS speaks the truth.

Yesterday, I tried to demo a proper stall (not the girly one) in a 320 sim..

We got down to (about) Vsw-30 kts before a good downward V/S developed. The recovery was normal but the sim would not fly anymore in spite of an indicated 210 kts.

It wasn't programmed for that manoeuvre and didn't expect to be asked.

from captain87
 

I think it would be the hardest abnormal situation to manage but it's nearly impossible to happen according the system's redundancy. A Triple Hyd Failure would mean that all the three systems have a leak and/or the engines are out with RAT locked in its IN position ... In this case I think that the Mechanical backup wouldn't be possible according the loss of the thrust levers efficiency that are hydralicaully operated.
I'm not sure ... but I believe this extreme situation should be out of consideration and I hope that the engineers have worked fine in order to avoid it.

captain87 (airline pilot student)

EB,

quote
There have been studies done (NASA?) with a view to someday include a "thrust only" reversion into future flight control software.
unquote

NASA (Dryden) developed the PCA (Propulsion Controlled Aircraft) concept using a MD-11 as testbed. There was a very nice article on this on an old Flight Internatinal magazine. The plane being controlled via the MCP, no need to direct handle the levers.

Some additional information: http://www.nasa.gov/centers/dryden/h.../PCA/md11.html

Cheers

BF

The green and yellow double failure seldomly occurs as two independent failures. Mostly the second failure is caused by the continuous operation of the PTU that connects both systems. Three simultanious failures are even more remote.

What should be of more concern than a loss of all hydraulics, is the apparent lack of understanding from qualified crews of how the primary flight controls of their aircraft function.

If the problem cant be solved with the QRH then you are in "no mans land" How it works is probably of of little use.
One instructor I had in the USA talked about the "BRT" levers. These were the thrust levers. " When you push the BRT levers forward the big round things make more noise, that all you need to know"

guys I think a real lot has to go wrong to be looking at this scenario. You would have to virtually empty out all three hydraulic systems. Pretty unlikely.

Two Engine driven pumps

One electric pump with a ptu to the other side

another electric pump on blue sys and a rat as back up........

thats a fair bit of redundancy.

Are you aware that already many HYD DUAL LOSS happened on 320?

Mostly G/Y, 'cause GREEN RSVR LOW LVL but YELLOW PTU kept running and overheating YELLOW SYS?

So it needs only one of these days without BLUE SYS.....

Look at the rudder system, all 3 hydraulic systems are operating very closely to each other, Souix City, Japan Airlines, both lost all systems from one problem. So why is everyone so certain it will never happen on a a320.
Murphys Law Anyone?
If it can happen, it WILL happen.

What you should be concern about is that a manufacturer like airbus do not even consider possible that one of his planes could suffer by a triple Hyd fail.
Infact, the Initial Airbus training (cbt) doesnt talk about it,the Fcom doesn talk about it.There is nowere any reference were you can get a secure reply about this question.
The only thing you can do is to go throw the aircraft systems charts (flight control) and say ah yes, with no hyd you are on the ground.

Pilots are human beings and it's not 1 month course for a type rating which would give them the full kwnoledge about the airplane tey will fly.
You need time, lot of study and questions like the one i have asked before say that you really know an aircraft.
And i am surely not the kind of person that would feel is the best just because i'm sitted on a 320.

cheers

Yes they do.

They do the maths and they come out with chances of it happenning so low, that it doesn't justify the installing of the fourth system.

Send PM to PBL, if you'd like to see actual numbers and methods of getting them.

However, PTU that doesn't shut itself off with HYD LO LVL is something that Airbus could have done bettter and I hope it will be rectified.

Would be interesting what the "maths" say about DUAL HYD SYS LOSS.....

Less than 10^-9 per flight hour. Just like other catastrophic failures.

Off the top of my head I can't think of a G and Y hyd failure that wasn't caused by inadvertent use of the PTU. Certainly it's the biggest cause by far. It's interesting that despite all the cries from pilots about over automation in FBW Airbuses, pilot control of the PTU is a problem. Should Airbus remove the PTU p/b and automate the system further to prevent overheating and a resulting dual hyd loss?

757 and 767 also have three hydraulic systems, albeit without a PTU.

Yes, it may be a problem. Are you aware that faulty PBs kept YELLOW PTUs running?

Pilot's fault?:ugh:

Most important things have been said.

NASA proved the concept of PCA, FAA desided that it's not justified. They have calculated all safety improvements and do the relation between costs and lifes saved. Those improvements with the most "lifes for the buck" get the nod.

hth,
Dani

Aside from that, IIRC the ECAM action for a G or Y hyd loss doesn't say turn off the PTU! And of course, in the event of a G or Y reservoir low quantity (or overheat) the PTU p/b will be shining away with a lovely 'FAULT' light. The PTU isn't FAULTy though and will be happily pumping the other system into a reservoir overheat. Moral of the story, know your systems.

Or maybe add some more logic to the PTU controller and remove the button altogether...? ;)

Giggey,

It was not meant as a personal attack, but more as an attack on the industry. There seems to be a move towards the "no need to know" philosophy, rather than the "need to know" one. I trust you understand the difference.

As a classically trained engineer, who do give ground courses to aircrews, I find the level of training, and basic knowledge of those participating, to be seriously lacking in one very important aspect, understanding! There is no emphasis on understanding. Complete the exercise and tick the box, that is what training seems to have become. Ham and Enos would have been right at home.

This thread, and many other, are examples of this.

Techman,

Three cheers!:D What is even worse, is there does not seem to be a place to go look it up either! While the aircraft systems of today can be so interconnected, it would be impossable to keep them all straight during an oral or PC, it would be great to have a "reference" manual that tells the real story.

It seems the older aircraft were built on the thought that the crew would be smarter than the aircraft, and today's aircraft are built on the, oh never mind.

By the scope of this thread, I assume that the cause of the triple failure is running all three systems dry. I'll see if I get some time in the simulator next week and see what ours does. I agree it might not be completely correct, but since the simulator models what happens with each system dry, it should be able to do it with all three empty. Also, some simulators have the real computers, they are just feed inputs.

AA DC-10 had a jammed stabilizer. Not the same as a total hydraulic loss but they were able to land using the #2 engine to change the pitch attitude. Using the wing mounted engines also has a pitching moment(power up, nose up, power back, nose down)

DC-10 into KSUX had total hydraulic failure. Read the NTSB witness statements, and not the final report. CKA Dennis Finch(sp?) saved the day.

A300 had total hydraulic failure after SAM impact. Did one go-around and then landed on the runway.

Total hydraulic failure is possible. It can be survivable but is tough to accomplish. I'm 2 out of 3 in my attempts. Fairly easy, very tough, and then a crash. :sad:

Try it and be humbled...

There are plenty of planes with 4 hydraulic systems.

A300 and DC10 have 3 redundant hydraulics. B747 and L1011 have 4. No one seems to have bothered with 5.

The JAL B747 which had a rear bulkhead explosion lost all 4 redundant hydraulic systems, just like the DC10 lost all 3 to tail engine explosion and the DHL A300 lost all 3 to a rocket hit in wingtip.

It follows that multiple common-cause failures are not an unlikely event - has happened 3 times already - you could be the fourth.

A320 has 3 hydraulic systems - like A300. But unlike A300 and A310, the A320 has glass cockpit, fly by wire and sidesticks.

If an A320 were to lose one wingtip and all three hydraulics just like the A300 did - how would the cockpit controls react?

Concerning maths, with almost 6.000 A320 delivered chances are getting high for a triple HYD LOSS.

Sim modelling
 

With regard to earlier posts about whether a sim would accurately reproduce the flight characteristics first airbus would have to establish exactly what those characteristics are.

Do you really think they are going to want to fly around with no hydraulics just to see what an extremely unlikely failure would be like?