A320 characteristics

[Tool Time]

The A320 exhibits four flight laws:
1. Normal Law
2. Alternate Law.
3. Direct Law.
4. Basic Law.

In the first three, it thinks it's a computer.
In the fourth, it thinks it's an aeroplane.

Assuming it's airborne, pull back in the stick, it goes up. Push forward on the stick, it goes down. Push right on the stick, it rolls right. Push left on the stick, it rolls left. Pust the rudder pedals, it yaws.
Push the thrust levers forward, it accelerates. Pull back on the thrust levers, it deccelerates.

Amazing isn't it.

[Veethree]

I think the Airbus test pilot that flew into the trees would probably disagree with you.

[Tool Time]

He wasn't flyng the aeroplane.
QED

[breguet]

veetrhee, The one flying into trees was an Air France 320 flown by two company pilots. The captain, however, if I remember, worked closely with Airbus to integrate the 320 in the Air France fleet.

[cokehead]

And your point was..............??

[enginefailure]

hey cokehead, exactly the same what i thaught
about this topic .....


cheers
ef

[B772]

Veethree. The A320 accident you refer to has been covered pretty well over the years. FYI the aircraft was an AF a/c F-GFKC MSN 009 which had only completed 22 hours and 15 cycles.

The AF crew were approved to do a flyover at 100' but the AF Management Capt descended to about 30' with engines at flight idle.

This level was below the level of obstacles in the area and at the time of impact the engine speed was 83% N1. 9After GA power applied)

The report was critical of the 'crew' and said late application of go-around power was partly to blame. It was a miracle that the accident only resulted in 3 fatalities out of 136 on board.

[FO Nigetrussoxide]

OK,everyone has the facts about that crash.
The one I'm interested in is the A330 that crashed during a test flight.
I simply wanted to understand what happened -from a technical viewpoint.
There doesn't seem to be a lot of info available (in the normal places).
Is that possibly because it was a non PT flight?

[alosaurus]

The A330 which crashed in Toulouse was on a test flight with an a/c std not released for service.The test in question should have been performed at a much higher altitude than the second segment scenario at which the single engine failure was initiated (and held intentionally with speed decaying rapidly).Nick Warner was within a couple of hundred feet of recovery.The A320 allegedly had multiple protection systems disabled and the CVR recorded the captain commenting about how his chief pilot would be unimpressed with his configuration.

[pom]

When the Airbus goes into Altitude Capture mode, it flies a computer controlled arc, based on the vertical speed at the time Alt Cap engaged. Unfortunately, the A320's climb above FL300 becomes a series of roller coaster rides, as it is trying to control TAS, but doesn't have enough elevator authority (0.1G) to follow it accurately. As a result it always enters Alt Cap mode during a vertical swoop, and then the speed drops alarmingly as it tries to follow its predetermined arc (with no airspeed input to the autopilot).

Basically, this is what happened in the Toulouse crash; the aircraft was trying to follow its predetermined arc without enough power to achieve it.

Boeings use the same technique, but as their autopilots have better elevator authority and they have a greater power reserve, it rarely causes problems.

[Fat Boy Sim]

Pom, Are you absolutely sure that all you have written is true?

[Three-Twenty]

It's not.

Tool time, check your 'facts' about the control laws, too.

I assume you mean 'mechanical back-up', not 'basic law'. And in fact in this mode the sidestick will not work AT ALL. Stick back - aeroplane does NOT go up...

The only input the computer has to the control response in normal law (when hand-flying) is to prevent overspeed (a gradual pitch-up at VMAX+18kt, so you are being a bit naughty anyway), and retracting spoilers and/or applying TOGA if you try to stall it.

Other laws just offer various stages of reduced protection and in fact in direct law the stick commends surface deflection, just like a real aeroplane. Ahhhh.

That is a bad thing if you particularly WANT to stall the aeroplane, I agree...

The chap with the aeroplane in the trees crasjed because he left it too late before appying TOGA. The engines were at about 89% when he crashed, but were on the way up from idle and he was v. slow and heavy to start with...

[jtr]

Ummmm... pom, if a light weight 330 on one donk, and TOGA, doesn`t have enough `power reserve` then I don`t think they would be certified.

FROM MEMORY>>The 330 crash was with a low stop ht, EFATO, with altitude acquisition, which did follow a precribed path as someone said. The aircraft ended up too close to VMCA, with an extreme C of G to boot.
The 330/340`S have altered software for alt capture (as a result), but on occaisions, the ALT * will still get you too close to (or below) green dot (best L/D)

[This message has been edited by jtr (edited 18 September 2000).]

[Iceman49]

330 from memory: They were testing new software which would allow you to have the autopilot engaged shortly after takeoff, lose an engine and then still continue to fly with the autopilot engaged. They had selected a low FCU altitude...failed the engine and "alt*" was annunciated. With the alt* engaged and auto pilot on, the FMS directs the autopilot to do what is necessary to capture the altitude...which could mean more of a pitch up. With the 1 eng out, the speed went below Vmca, and they were unable to recover in time. Part of the problem also was that they had performed several other eng out, autopilot engaged climbs with the FCU altitude set much higher...thus not engaging alt*.

[alosaurus]

Pom-do you work in Seattle?A330 crash caused by defective pre production software and a development test (designed to interogate its integrity)being initiated well below a level approved by all aviation authorities.A single engine A330,with a test crew and no balast, has rather more power than it actually needs.The aircraft came to rest in the middle of the airfield and narrowly missed the A330/340 final assembly building.

[atomic]

Hey Three-Twenty. It's not just that you have protections in normal law. Even though the end result is the same, in normal law, the roll input with the stick signals the computer to apply a certain rate of roll, not a certain deflection of maximum of the control surface. Pitch is at all times g protected. And very important: Flight path stability. Increase the thrust inlevel flight and it stays where it is and keeps on going where you pointed it. No pitch up like in conventional planes. Point the nose to a 5 degree climb and it stays there and does whatever it has to do with the flight control surfaces to maintain this vector.
Maybe I understood you incorrectly, but there's more to normal law than just limit protections.

[atomic]

The way I understood this thing with the A320 crash in France was that they were waiting for the protection offered by the Auto-Throttle System to kick in: 'Alpha Floor'. In the low speed/high AOA protection mode (the yellow/black band on the airspeed indicates that when we are entering this mode), the autopilot kicks off, nose up trim is inhibited, the max bank angle is reduced to 45 degrees. The side stick now controls AOA directly. Whe speed is reduced further, then, with an operable auto thrust system on the plane, the system will increase thrust to TOGA when this 'alpha floor' is reached.
I guess those guys were waiting for this automatic protection to kick in (for demo purposes) but nothing happened. Why?? It is disabled below 100' RA not to accidentally add TOGA thrust when you're about to land the plane and have gotten a bit slow during the flare. Wouldn't it have been in the landing configuration, the thrust would have kicked in. While they were waiting for this, the trees came closer and when they finally increased thrust manually, it was too late.
On the A319, by the way, this function is inhibited with single engine and Flaps/Slats in Config 1 or greater, I gues due to the limited rudder ability to counter the yaw at slower speeds with the shorter fuselage, even though the max deflection is 30 degrees instead of 20 on the A320.