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A320 Low speed stability

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A320 Low speed stability

Old 27th Mar 2009, 15:12
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A320 Low speed stability

While reading about the low speed stability, the following question arose, as nothing is explicitly said about it.

During Low speed stability (replaces AoA protection when in alternate law)a gentle nose down signal is intoduced between 5 to 10 knots above stall speed to keep the speed from falling below these values. Can the pilot override this, or not?

Thanks in advance,
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Old 27th Mar 2009, 15:19
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I reckon, the nose down and throttle up would happen...so would return back to nose up after a short period
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Old 27th Mar 2009, 15:31
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The A320 pilot can can override either low or high speed stability with moderate stick inputs. At least that's how it works on A320 sim, I've never flown real 320 in altn law.
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Old 27th Mar 2009, 15:34
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Thanks my man. So the bus can get into a stall in alternate law? No need for direct law.
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Old 27th Mar 2009, 15:39
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If you keep pulling, yes.
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Old 27th Mar 2009, 15:44
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Gracias otra vez!!!
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Old 27th Mar 2009, 15:58
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Niets te danken.
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Old 27th Mar 2009, 16:52
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Would the A320 Increase the throttles also if you continued pulling back near the stall?
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Old 27th Mar 2009, 17:11
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It wouldn't in alternate and direct laws. Automatic setting of TOGA thrust, known as alpha floor is available only in normal law, when alpha protection prevents the pilot from stalling the aeroplane and alpha prot can't be overriden by the stick input anyway.
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Old 27th Mar 2009, 17:44
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Thanks, I understand now I'm not an A320 pilot, just a PPL but I am very interested in learning about these things
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Old 27th Mar 2009, 22:15
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A lawyer for the law

Gentlemen,
Can someone me explain how to get in the so called >alternate< or >direct< law in air ??

Please read once more yr manual before telling somebody such a thing.
There is no direct law in air. How do U want to get in ? Only when U loose all Prims and Secs, but than U have only mechanical inputs.

Of course can the pilot be so unlucky to get in a situation, where normal law in pitch control failed , but than alpha 1 Prot takes over, when this fails , Vc Prot comes, this is overideable in lowspeed only.

But for this we have the high paid chimps

Logic for the elec control is PRIM1>2>3>SEC1>2
Normal>alternate>protection and direct on GRD

Now calculate the possibility and praise Airbus

Sorry but direct law in air is a misunderstanding of the philosophy

rgds
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Old 27th Mar 2009, 22:36
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Are you really talking about Airbus?

Everytime you are in alternate and lower the gear you are in direct mode. So it's pretty important to know what to do in direct law.

Or do you lower the gear on ground only?

dani
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Old 28th Mar 2009, 00:06
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Can someone me explain how to get in the so called >alternate< or >direct< law in air ??
They're not "so called", this is official Airbus terminology. FCOM 1.27.30 has it very neatly explained.

So, has the Airbus really changed FBW arhitecture on latest A320s from FAC/ELAC/SEC to PRIM/SEC, or what we have here is the charge of the MSFS brigade?
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Old 28th Mar 2009, 02:46
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They're not "so called", this is official Airbus terminology. FCOM 1.27.30 has it ver

DEAR ALL

pls check once more yr manuals, for a so called direct law U need
-triple ir fault
-triple prim fail
-two elev fault
-both eng out

in all other failure/law configs U have still protections, in alternate mode the AOA protection is still there. RYFM

Ground mode or direct law for pitch control is till 8 sec after liftoff, from 100 ft down to ground U swap into flare mode, touchdown + 2 sec direct law.
So U R really unhappy when U get >>>direct law<<< in flight !!!

rgds
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Old 28th Mar 2009, 03:55
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Please read once more yr manual before telling somebody such a thing.
There is no direct law in air
You must specify between the A320 and A330, the A320 can degrade to Direct Law while in flight.
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Old 28th Mar 2009, 05:47
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A330 and 340 can too. FCOM 1.27.30 FLIGHT CONTROLS - RECONFIGURATION CONTROL LAWS refers, no matter whether it's 320, 330 or 340 manual. Getting into direct law while airborne on TA Airbi is very unlikely yet it's possible.

What's the name of the thread, anyway?
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Old 28th Mar 2009, 06:48
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All Fly by wire Airbus airplanes can end up in direct law in flight. On the A320 series it is a bit more common though than on the A330/340 as the architecture of the flight control computers is less sophisticated. On the A320 if you loose both flight augmentation computers (FAC) in flight you revert back into alternate law and upon landing gear extension into direct law. On the A330/340 a simple dual radio altimeter fault will have you ending up in direct law upon landing gear extension when the autopilot is switched OFF, we practice this exercise in the simulator. Low speed and high speed stability on all fly by wire Airbus can be overridden by the pilot and since alpha floor is not available in alternate and direct law the aircraft will stall.
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Old 28th Mar 2009, 13:37
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Thanks for correcting me.
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Old 29th Mar 2009, 10:53
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Not to forget if you have duar RA fault, when you extend the gear, the aircraft will go from Normal law to Direct law.
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Old 29th Mar 2009, 14:30
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Read the question before answering...

h3dxb, have you read the title of this thread?

We're talking A320 here, not A330! So no PRIM, no SEC's (and I mean Secondary Flight Control Computer not Spoilers Elevator Computer)...on A320.

It's quite feasible to end in Direct law on A320, and far more unprobable on A330 I admit.
If a failure leads you to fly in alternate law, you WILL end in Direct Law once the gear is down, why? Because there is no Flare law in ALTN law, the only way to flare the aircraft is to put it in Direct law...it has been designed like that.

But again, the related topic is on A320, not A330/340.

Edit: this msg is redondant with ALK's...saw it after.
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