This week Matt and Andy take a look at the Flight Augmentation Computers and their functions.

New Airbus manuals are now released and on their way to airlines around the world. Your airline should be updating them soon if they haven't already. There's an episode about this change TAP030 so have a listen to refresh your memory.

The A320 has two FACs (flight augmentation computers) and they have three main functions, - Yaw functions (your damping, rudder trim and rudder trim limiting)

- Flight envelope functions

- Windshear detection

 

The FACs govern the flight envelope, rudder position display and rudder trim indications regardless of what the flight crew does with the FAC pushbutton. It also controls the speed scale.

FAC Computes:

VSW

VLS

VFE & VFE NEXT

VLE

VMO/MMO

GREEN DOT

S SPEED

F SPEED

TREND ARROW

 

Alpha lock

This function inhibits slat retraction at high angles of attack and low speeds. When the flat leave is set to 0, the alpha/speed lock function activates and inhibits slat retraction if:

The angle of attack is greater than 8.5° or

The speed is less than 148 kts.

 

If the flap lever is already set to 0 (so the slats are moving or are already at 0) when the alpha lock conditions occur, inhibit will not activate therefore the stats will continue to retract or remain at zero.

Once the alpha/speed lock function is active, the slats will only retract when:

The angle of attack is less than 7.6° and,

This speed is above 154 kts

The function is not active on the ground when the speed is less than 60kts.

 

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