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Old 27th Dec 2007, 12:18   #1 (permalink)
 
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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.
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Old 27th Dec 2007, 12:34   #2 (permalink)
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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
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Old 27th Dec 2007, 13:02   #3 (permalink)
 
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Quote:
B. Just with rudder and Diff. Thrust
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?
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Old 27th Dec 2007, 13:37   #4 (permalink)
 
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There have been plenty of DUAL HYD SYS LOSS (G/Y).

It's only a matter of time until a tripple happens.....
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Old 27th Dec 2007, 14:05   #5 (permalink)
 
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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
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Old 27th Dec 2007, 14:05   #6 (permalink)
 
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different frame but did someone say sioux city

http://en.wikipedia.org/wiki/United_Airlines_Flight_232
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Old 27th Dec 2007, 14:14   #7 (permalink)
 
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I checked it on Fcom and even the rudder is operated hydraulically than with the 3 sys inop even the rudder is gone.

gj
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Old 27th Dec 2007, 14:28   #8 (permalink)
 
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Quote:
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.
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
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Old 27th Dec 2007, 17:11   #9 (permalink)
 
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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....
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Old 27th Dec 2007, 20:13   #10 (permalink)
 
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Quote:
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
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Old 27th Dec 2007, 21:13   #11 (permalink)
 
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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
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Old 27th Dec 2007, 21:43   #12 (permalink)
 
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Quote:
And do you really think the Sim is accurately modelled with no Hydraulics
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.
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Old 28th Dec 2007, 01:41   #13 (permalink)
 
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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.
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Old 28th Dec 2007, 14:17   #14 (permalink)
 
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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.
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Old 28th Dec 2007, 16:25   #16 (permalink)
 
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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!
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Old 28th Dec 2007, 16:49   #17 (permalink)
 
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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.
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Old 28th Dec 2007, 16:57   #18 (permalink)
 
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Quote:
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...
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.
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Old 28th Dec 2007, 19:44   #19 (permalink)

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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.
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Old 29th Dec 2007, 07:32   #20 (permalink)
 
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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)
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