SIDE STICK AND PRIORITY LOGIC ON A320

Side sticks, one on each lateral console, are used for manual pitch and roll control. They are spring loaded to neutral. When the autopilot is engaged, a solenoid-operated detent locks both side sticks in the neutral position. If the pilot applies a force above a given threshold (5daN in pitch, 3.5 daN in roll), the autopilot disengages and the side stick unlocks and sends an input to the computers.

The hand grip includes 2 P/Bs: An autopilot disconnect/side stick priority P/B and a push-to-talk button. Side stick priority logic: When only one pilot operates the side stick, his demand is sent to the computers. When the other pilot operates his side stick, in the same or opposite direction, both pilot inputs are algebraically added. The addition is limited to single-stick maximum deflection.

In the event of simultaneous inputs on both side sticks (2° deflection off the neutral position in any direction), the two green SIDE STICK PRIORITY lights, on the glare shield, come on and the "DUAL INPUT" voice message activates. A pilot can deactivate the other side stick, and take full control by pressing and keeping pressed his takeover P/B. For latching the priority condition, it is recommended that the takeover P/B be pressed for more than 40 seconds. The takeover pushbutton can then be released without losing priority. However, a deactivated side stick can be reactivated at any time, by momentarily pressing either takeover P/B. If both pilots press their takeover P/Bs, the last pilot to press their P/B will have priority.

If an autopilot is engaged, any action on a takeover P/B will disengage it. In a priority situation, a red light will come on, in front of the pilot whose side stick is deactivated. A green light will come on, in front of the pilot who has taken control, if the other side stick is not in the neutral position (to indicate a potential and unwanted control demand).

If one stick is deactivated on ground, at takeoff thrust application, the takeoff «CONFIG» warning is triggered.