# What is the input range of common fly-by-wire controls?

What's the range that typical fly-by-wire controls (let's take A320 and B777 as examples) allow inputs in?

The A320 controls in the y-axis of the side stick (forward/backward axis) the g load - what's the minimal g load you can input when pushing the stick fully forward / the maximum when pulling it fully backwards? Is this a fixed value or does it depend on factors like speed (IAS / TAS / ...), attitude, altitude / air density or anything / ...? Or is it just the maximum value that the flight controls could give you at any moment?

Same for roll rate, what's the maximum you can command there? And for the B777, it's basically the same question except for the yoke instead of the sidestick.

Also, is the relation between control input (side stick movement / yoke movement) and controlled variable (g-force, roll rate, ...) a linear curve? I.e., if the side stick gives you at the neutral position 1g and e.g. 1cm backwards it gives you 1.1g, does 2cm backwards give you 1.2g?

• Fly by wire systems do not define maximums by the deflection of the control input. The system will detect what the pilot wants to do but in extreme cases will limit the changes and rate of those changes in attitude to the safe limits of the aircraft. Apr 22, 2019 at 19:07

### A320

Max/min stick g:

+2.5 g to -1 g for clean configuration.
+2 g to 0 for other configurations.

Roll:

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

And as it says, is proportional to deflection. (Source: A320 FCOM)

### 777

I checked the 777's FCOM but did not find similar stated values/explanation.

Since there are trim switches on the 777's yoke, unlike the lack thereof on the A320's stick, the trim switches change the reference speed, and the thrust levers command pitch change. It's designed to mimic, say a Cessna: adding power pitches up; trimming down increases speed.

The trim reference speed is the speed at which the airplane would eventually stabilize if there were no control column inputs. Once the control column forces are trimmed to zero, the airplane maintains a constant speed with no column inputs. Thrust changes result in a relatively constant indicated airspeed climb or descent, with no trim inputs needed unless airspeed changes.