Systems Guide

Aerosoft
Airbus A320/A321
SYSTEMS
Systems guide
Vol
4
04-03-14
28 October 2014
used to control a specific vertical path, autothrust uses variable thrust to maintain target speed. When manually
flown in fixed autothrust mode the flight director’s pitch command bar indicates the pitch needed to fly the
desired speed.
ALPHA FLOOR
The alpha floor protection assists the pilot in recovering from dangerous low speed and high angle of attack by
automatically setting TOGA thrust when:
 Excessive angle of attack (alpha)
 Excessive high nose up attitude
 Windshear is detected
When the alpha floor conditions are no longer detected the autothrust system will stay in TOGA lock until the
pilot disables auto throttle. It is recommended the pilot moves the throttle to the TOGA detent before depressing
the FCU A/THR pb to avoid a power surge. After that the pilot can pull the throttle to the CL indent and engage
the autothrust.
FLIGHT AUGMENTATION COMPUTERS
The FACs handle:
 Yaw damping and turn coordination
 Rudder trim
 Flight envelope and maneuvering speed computations
 Alpha floor protection
 Windshear detection
 Low energy detection
FLIGHT ENVELOPE
Many different speeds are calculated by the FACs are used by the autoflight system. These speeds include the
minimum safe speed, maximum speed and never exceed speed. They also calculate the alpha floor speed. Most
of these speeds are shown on the PFD airspeed indicator.
WINDSHEAR
The FACs will try to detect windshear and will warn the pilot of this dangerous condition. Windshear detection is
only active below 1300 feet AGL in configuration 1 or greater. When detected the flight director will show an
optimal pitch attitude and the aural warning “WINDSHEAR” will be heard.
LOW ENERGY WARNING
Between 2000 and 100 feet AGL the FACs will detect a low energy state (based on airspeed, descent angle and
angle of attack) and will warn the pilot with an aural “SPEED SPEED SPEED” warning. Normally this warning will
precede an alpha floor condition.
FLIGHT GUIDANCE