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Old 29th Sep 2014, 08:53
  #472 (permalink)  
rudderrudderrat
 
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If that pulsing is recommended by airbus (which i doubt until proof is shown) there should be an explanation available to this steering method we all would sure be interested in.
FCTM OP-020 Flight Controls
Normal Law.

"OPERATIONAL RECOMMENDATION:
From the moment the aircraft is stable and auto-trimmed, the PF needs to perform minor corrections on the sidestick, if the aircraft deviates from its intended flight path.
The PF should not force the sidestick, or overcontrol it. If the PF suspects an overcontrol, they should release the sidestick.
AT TAKEOFF AND LANDING
The above-mentioned pitch law is not the most appropriate for takeoff and flare, because the stable flight path is not what the PF naturally expects.
Therefore, the computers automatically adapt the control laws to the flight phases:
GROUND LAW: The control law is direct law
FLARE LAW: The control law is a pitch demand law.
OPERATIONAL RECOMMENDATION:
Takeoff and landing maneuvers are naturally achieved. For example, a flare requires the PF to apply permanent aft pressure on the sidestick, in order to achieve a progressive flare. Whereas, derotation consists of smoothly flying the nose gear down, by applying slight aft pressure on the sidestick."

Alternate Law.
"Alternate law characteristics (usually triggered in case of a dual failure):
In pitch: same as in normal law with FLARE in DIRECT
In roll: Roll DIRECT
Most protections are lost, except Load factor protection.
At the flight envelope limit, the aircraft is not protected, i.e.:
In high speed, natural aircraft static stability is restored with an overspeed warning
In low speed (at a speed threshold that is below VLS), the automatic pitch trim stops and natural longitudinal static stability is restored, with a stall warning at 1.03 VS1G.
In certain failure cases, such as the loss of VS1G computation or the loss of two ADRs, the longitudinal static stability cannot be restored at low speed. In the case of a loss of three ADRs, it cannot be restored at high speed.
In alternate law, VMO setting is reduced to 320 kt, and α FLOOR is inhibited."

In Normal Law, most pilots use the "pulsing" method i.e. they release the side stick between attitude changes.

In ALT Law, FCTM says roll is DIRECT but makes no recommendation on how to handle it.
Bonin seems to have found the difference in handling qualities to be significant.
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