Originally Posted by OATNetjets
Boofhead I do not see your point:
1 - On the FBW airbus fleet the sidesticks DO move,
Well, they move when the pilots move them. They are spring-centered, and neither backdriven nor coupled.
and near the ground you will get direct control law on the lateral axis.
No you won't. Reversion to ground mode (direct law) is
after touchdown.
This means that you get roll control surfaces displacement proportional to the stick inputs, as in any other airliner.
No. Stick displacement controls roll-demand.
In addition to FCOM quotes in recent posts by Right Way Up and me, showing that normal law remains active until touchdown, here are some more interesting tidbits from FCOM Bulletin 54/2, of June 2002:
Originally Posted by A320 FCOM Bulletin No. 54/2
Subject: Aircraft Handling in Final Approach
General
The purpose of this FCOM bulletin is to highlight certain aspects of aircraft handling during final approach, and to illustrate that the feedback received from in service experience merits further attention.
[...]
Aircraft Handling on the Lateral Axis
Generally speaking, lateral handling of fly-by-wire aircraft is conventional. But, in very gusty conditions, it is necessary to recall the principle of the flight control law in roll. With the sidestick, the pilot can order a roll rate up to a maximum of 15°/second. However, the aerodynamic capacity of the roll surfaces, when fully deflected, is much higher: that is, up to about 40°/second. This means that, if the aircraft is flying through turbulence that produces a roll rate of 25°/second to the right, the aircraft still has the capacity to roll to the left at a rate of 15°/second, with full sidestick command. This is more than what is necessary in the worst conditions.
The sidestick's ergonomical design is such that the stop at full deflection is easily reached. This may give the pilot the impression that the aircraft is limited in roll authority, because there is a time delay before the pilot feels the result of his/her action. In conventional aircraft, due to the control wheel inertia, the pilot needs considerably more time to reach the flight control stop.
The fly-by-wire system counteracts the effects of gust, even with the sidestick in the neutral position ; the pilot's task is to give overall corrective orders. In other words, the pilot should smoothen and filter inputs and should resist moving the sidestick from one stop to the other.
Every sidestick input is a roll rate demand, superimposed on the roll corrections already initiated by the fly-by-wire system. The pilot should only apply "longer-term" corrections as needed.
Before flare height, heading corrections should only be made with roll. As small bank angles are possible and acceptable close to the ground, only small heading changes can be envisaged. Otherwise, a go-around should be initiated.
Use of rudder, combined with roll inputs, should be avoided, since this may significantly increase the pilot's lateral handling tasks. Rudder use should be limited to the "de-crab" maneuver in case of crosswind, while maintaining the wings level, with the sidestick in the roll axis.
[...]
Bernd