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LeCoqFrancais
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Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 5:55 am

A Singapore Airlines Airbus A350-900, registration 9V-SMC performing flight SQ-323 from Amsterdam (Netherlands) to Singapore (Singapore), was descending towards Singapore, when the crew requested a tow to be ready for landing advising they would not be able to vacate the runway. The aircraft landed on Singapore’s runway 20C, braked firmly and came to a stop about 2100 meters down the runway, but was unable to vacate the runway. The aircraft was towed to the apron about 20 minutes later. In the meantime all landing traffic was using runway 20R.

http://www.aviationgazette.com/singapor ... c-failure/
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LAX772LR
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Re: Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 6:09 am

Scary

The flaps remained extended

Well, that's good. Does the A359 have a locking mechanism for the flaps to stay down once commanded, in the event of a total hydraulic failure thereafter?

I doubt that there's a way to lower them in the event of a total such failure beforehand, but I'd be interested to know what sort of major design changes (if any) were made post UA232, for this type of thing.
I myself, suspect a more prosaic motive... ~Thranduil
 
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LeCoqFrancais
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Re: Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 6:35 am

LAX772LR wrote:
Scary

The flaps remained extended

Well, that's good. Does the A359 have a locking mechanism for the flaps to stay down once commanded, in the event of a total hydraulic failure thereafter?

I doubt that there's a way to lower them in the event of a total such failure beforehand, but I'd be interested to know what sort of major design changes (if any) were made post UA232, for this type of thing.

I believe such a system is on the 737NG, and if that is the case, I doubt that the A350XWB would not have such a system.
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LAX772LR
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Re: Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 7:46 am

LeCoqFrancais wrote:
I believe such a system is on the 737NG, and if that is the case, I doubt that the A350XWB would not have such a system.

From what I understood, such systems in the 737, MD80, etc will keep the slats extended, but my question is about the flaps.

I wasn't aware of either of them having such a mechanism. Could easily be wrong though.
I myself, suspect a more prosaic motive... ~Thranduil
 
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Starlionblue
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Re: Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 8:19 am

The 350 has 2 hydraulic systems. It can lose both and still fly. AFAIK you even keep the autopilot with a dual failure. Sounds way less dramatic than a dual failure in an older generation aircraft with 3 systems.

Failures do happen and if you lose the system that operates the nose wheel steering you need to be towed off.

LAX772LR wrote:
Scary

The flaps remained extended

Well, that's good. Does the A359 have a locking mechanism for the flaps to stay down once commanded, in the event of a total hydraulic failure thereafter?

I doubt that there's a way to lower them in the event of a total such failure beforehand, but I'd be interested to know what sort of major design changes (if any) were made post UA232, for this type of thing.


While landing with no or limited flaps is hardly ideal, it is certainly possible. I might be wrong but I think the 350 has electric backup actuation on the slats.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
hayzel777
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Re: Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 11:30 am

The plane is brand new. How could these types of problems arise already? Not even 1 month old and they are already experiencing major mechanical issues.
 
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moo
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Re: Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 11:36 am

hayzel777 wrote:
The plane is brand new. How could these types of problems arise already? Not even 1 month old and they are already experiencing major mechanical issues.


Some parts fail well before their "mean time between failure" rating - hence the use of the term "mean".

You get this with everything - it just makes the news when its something like this.
 
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zeke
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Re: Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 12:02 pm

Does the A359 have a locking mechanism for the flaps to stay down once commanded, in the event of a total hydraulic failure thereafter?


Yes its called the Power Off Brake. The Power Off Brake when set, mechanically locks the transmission shaft from its associated motor to the
gearbox, when the slats (flaps) have reached the selected position, in the case of runaway or asymmetry, or in the case of a power supply failure of a motor.

I doubt that there's a way to lower them in the event of a total such failure beforehand, but I'd be interested to know what sort of major design changes (if any) were made post UA232, for this type of thing.


In the event of total hydraulic failure of the green and yellow systems, the outer flaps can still be deployed by electrical motors. I would suggest this was a yellow hydraulic pump on engine #2 that failed (hence no nose wheel steering), they would still have had the other hydraulic circuit.

hayzel777 wrote:
The plane is brand new. How could these types of problems arise already?


These sort of things happen more regularly than people are aware, to me this is more of an inconvenience. I would expect more of these sort of issues to show up while the aircraft becomes more mature.
“Don't be a show-off. Never be too proud to turn back. There are old pilots and bold pilots, but no old, bold pilots.” E. Hamilton Lee, 1949
 
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BartSimpson
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Re: Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 12:40 pm

What I don't understand - please help me out - is exactly why they weren't able to vacate the runway. Was steering affected?
 
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KarelXWB
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Re: Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 12:49 pm

zeke wrote:
These sort of things happen more regularly than people are aware, to me this is more of an inconvenience. I would expect more of these sort of issues to show up while the aircraft becomes more mature.


Hydraulic failures are quite common. Hydraulic problems from the last 7 days per http://avherald.com/ :

> United B763 near Dublin on Jun 19th 2016, hydraulic problem
> Singapore A359 at Singapore on Jun 18th 2016, hydraulic failure
> Canada E190 near Toronto on May 26th 2016, hydraulic failure and leak
> United B763 at Newark and Munich on Jun 15th 2016, hydraulic problems
> SAA A319 at Johannesburg on Jun 12th 2016, hydraulic failure
> Jin B738 at Osaka on Jun 13th 2016, hydraulic failure
> Vueling A320 near Malaga on Jun 11th 2016, hydraulic failure
> Expressjet CRJ2 at Newark on Jun 12th 2016, hydraulic failure
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Laddie
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Re: Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 2:38 pm

In the event of total hydraulic failure of the green and yellow systems, the outer flaps can still be deployed by electrical motors.

Can you check this statement? It is my understanding the A350's inboard and outboard flaps are powered by the Yellow and Green hydraulic systems, without an electrical tertiary backup. Flight control systems with electrical backup: inboard ailerons, one pair of spoilers, elevators, rudder, and slats.
 
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scbriml
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Re: Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 3:30 pm

LAX772LR wrote:
Scary


What was scary about it and who was scared? :?:
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Stitch
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Re: Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 3:38 pm

BartSimpson wrote:
What I don't understand - please help me out - is exactly why they weren't able to vacate the runway. Was steering affected?


Yes. The nosewheel could not be steered due to the hydraulic failure.
 
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litz
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Re: Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 6:10 pm

Presumably there is some sort of fail-safe that locks the nose gear into a "straight ahead" position, so you don't find yourself heading off the runway?

Or does the rudder provide enough authority that this isn't required?
 
rcair1
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Re: Aviation Gazette: Singapore Airlines Airbus A350XWB has hydraulic failure

Mon Jun 20, 2016 6:16 pm

The rudder provides authority only down to a certain airspeed.
The nosewheel will castor to straight by default. Of course, if you have significant cross wind it can be interesting, but remember, you have differential brakes. You can brake on one side or the other.
rcair1

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