Re: Airbus A320 flight controls

From: (Francis JAMBON)
Organization: CLIPS-IMAG, Grenoble, France
Date:         10 Feb 96 12:30:58 
References:   1 2 3
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In article (Dans l'article) <airliners.1996.133@ohare.Chicago.COM>, (C. Marin Faure) wrote (=E9crivait)=A0:

> I had heard the left-plus-right-equals-nothing formula was the case on the
> original version of the system, but that it has subsequently been
> changed.

I don't know if the "side stick priority logic" has been changed but I
have found these informations from a rather old FCOM :

1.27.40 - P 3 - REV 16 - SEQ 002 - "For training only"


Sidesticks, one on each lateral console, are used for manual pitch and
rool control.
They are springloaded to neutral.
When the A/P is engaged a solenoid operated detend locks both side sitcks
in the neutral position. If the pilot applies a force above a given
threshold (5 daN in pitch, 3.5 daN in roll) the stick becomes free and A/P

(picture of one sidestick deleted)

Side stick priority logic :
- When only one pilot operates the sidestick :
  His demand is sent to the computers.
- When the other pilot operates his sidestick in the same or opposite
  direction both pilots inputs are algebraically added. The assition is
  limited to single sitck maximum deflexion.

A pilot can desactivate the other sick and take full control by pressing
and keeping pressed his priority takeover pushbutton.
If a takeover push button is pressed more than 30 seconds the system will
latch, thus allowing the push button to be released without losing priority.
However, at any time, a desactivate stick can be reactivated by momentarily
pressing its takeover push button.
If both pilots press their takeover pushbuttons, the last pilot to press will
get the priority.

Note: If an auto pilot is engaged, the first action on a take over push button
----- will disengage it.

In a priority situation
- A red light will come on in front of the pilot whose stick is desactivated
- A green light will come on in front of the pilot who has taken control,
if the other stick is not in the neural position (to indicate a potential
and unwanted control demand).

Note: If, on ground at take off application, one stick is desactivated,
----- the <<take off CONFIG>> warning is triggered.

--- end of FCOM page ---

Hope it helps. Don't ask me where I've found the FCOM.


Francis JAMBON              |    Equipe Ingenierie des Interfaces Homme-Machine
<>    |       Human-Computer Interfaces Engineering Group
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