# Does joystick position control bank angle in some Airbus aircraft? And what happens when the pilot deflects the joystick when wheels are on ground?

Does joystick position control bank angle rather than directly controlling aileron/spoileron deflection in some Airbus aircraft?

Also, what happens when the pilot deflects the joystick when the all wheels are on the ground and the bank angle (or roll rate) cannot change substantially?

Also, if the pilot is landing and the left main undercarriage assemblies are not extended for some reason, when the wheels on the right main undercarriage assemblies touch the ground, will maintaining a strong right control input on the joystick help delay the left wingtip (or engine nacelle) from contacting the runway, or not?

• On all FBW Airbus, the sidestick lateral position normally controls roll rate, not aileron deflection. Only in ground mode of Normal Law, ALT2 and Direct Law does the lateral position control aileron deflection directly. AFAIK there is no mode where sidestick position controls bank angle. Wikipedia article on Airbus control laws. Commented Mar 21, 2020 at 3:22
• What makes you think joystick position controls bank angle? It would be useful if you could provide an example or source for that claim Commented Mar 21, 2020 at 6:43
• @J.Hougaard - thanks, have edited, not in a way affecting any existing answer. Commented Mar 21, 2020 at 13:51
• Great answers, sorry that there is no +2 or +10 option. Commented Mar 21, 2020 at 18:52

Does joystick position control bank angle rather than directly controlling aileron/spoileron deflection in some Airbus aircraft?

To complement @Bianfable's answer, in Normal Law Flight Mode, Airbus FBW families (including A220) command roll rate via lateral stick position up to the artificial spiral stability limit of 33 deg bank (for A220 it's 30 deg). Below 33 deg bank, the aircraft exhibits neutral spiral stability; beyond 33 deg bank, it exhibits positive spiral stability, and lateral stick position commands a steady-state bank angle up to the roll limit of 66 deg (for A220 it's 80 deg).

Also, what happens when the pilot deflects the joystick when the all wheels are on the ground and the bank angle (or roll rate) cannot change substantially?

Upon landing, the Normal Law transitions to Ground Mode, whereby the stick inputs command direct control surface movements. For A320, the lateral control transitions from Flight Mode to Ground Mode in 0.5 sec on ground detection is met, as shown below:

Also, if the pilot is landing and the left main undercarriage assemblies are not extended for some reason, when the wheels on the right main undercarriage assemblies touch the ground, will maintaining a strong right control input on the joystick help delay the left wingtip (or engine nacelle) from contacting the runway, or not?

From this German accident report, in the case of an asymmetric gear deployment, ground signal is generated if "both LGCIUs (Landing Gear Control Interface Unit) detect that one landing gear has been lowered and is under load, and the radio altimeter measures the height above ground as less than 50 ft".

Therefore, immediately upon touchdown, you can expect the FBW to partially resist roll motion; but after 0.5 sec, you will have to use lateral stick to hold the aircraft level until the airspeed is too low to do so.

The sidestick (they don't like it when you call it joystick) is not controlling bank angle, but roll rate in flight. On the ground, the control surfaces are deflected proportionally to sidestick movement in order to perform a check of all surfaces before takeoff.

The details may vary, but this is generally true for all full fly-by-wire Airbuses. From the Airbus A320 FCOM:

Normal Law

When the aircraft is on the ground (in "on ground" mode), the sidestick commands the aileron and roll spoiler surface deflection. The amount of control surface deflection that results from a given amount of sidestick deflection depends upon aircraft speed. The pedals control rudder deflection through a direct mechanical linkage.

When the aircraft is in the "in flight" mode, normal law combines control of the ailerons, spoilers (except N° 1 spoilers), and rudder (for turn coordination) in the sidestick. While the system thereby gives the pilot control of the roll and heading, it also limits the roll rate and bank angle, coordinates the turns, and damps the dutch roll.

The roll rate requested by the pilot during flight is proportional to the sidestick deflection, with a maximum rate of 15° per second when the sidestick is at the stop.

When the aircraft is in "flare" mode, the lateral control is the same as in "in flight" mode.

(A320 FCOM - Flight Controls - Lateral Control, emphasis mine)

Similar for the A380:

Ground Law

The objective of the lateral ground law is to facilitate aircraft handling on ground.

The lateral ground law is a full authority control law in roll and yaw, with some yaw damping.

However, for small sidestick deflections, the lateral ground law helps the pilot to keep a small bank angle (less than 2 °), using only the ailerons. In particular, when the sidestick is at neutral, the law will aim to keep the wings level.

When rudder pedal deflection is close to maximum, yaw damping is removed.

The ground law is gradually phased in during 5 s after touchdown.

[...]

Flight Law
Roll Rate Demand

In manual flight, the normal law provides aileron and spoiler control from the sidesticks, to achieve a roll rate which is proportional to the sidestick deflection, independent of the aircraft speed.

With a full sidestick deflection, the maximum achievable roll rate is 15 °/s.

(A380 FCOM - Flight Controls - Flight Control System - Normal Law)