OPERATIONAL PHILOSOPHY
FLIGHT CONTROLS
A318/A319/A320/A321
FLIGHT CREW TRAINING MANUAL
High AOA protection is an aerodynamic protection:
? The PF will notice if the normal flight envelope is exceeded for any reason, because the autopitch trim will stop, the aircraft will sink to maintain its current AOA (alpha PROT, strong static stability), and a significant change in aircraft behavior will occur.
? If the PF then pulls the sidestick full aft, a maximum AOA (approximately corresponding to CL Max) is commanded. In addition, the speedbrakes will automatically retract, if extended.
airbus AOA PROTECTION
OPERATIONAL PHILOSOPHY
FLIGHT CONTROLS
A318/A319/A320/A321
FLIGHT CREW TRAINING MANUAL
In addition to this aerodynamic protection, there are three more energy features:
? If ATHR is in SPEED mode, the speed cannot drop below VLS, even if the target speed is below VLS
? An aural low-energy "SPEED SPEED SPEED" warning, warms the flight crew that the energy of the aircraft is below a threshold under which they will have to increase thrust, in order to regain a positive flight path angle through pitch control. It is available in CONF 2, CONF 3, and CONF FULL.
The FAC computes the energy level with the following inputs: ‐ Aircraft configuration
‐ Horizontal deceleration rate
‐ Flight path angle
For example, if the aircraft decelerates at 1 kt/sec, and:
‐ The FPA is -3 °, the alert will trigger at approximately VLS -8, ‐ The FPA is -4 °, the alert will trigger at approximately VLS -2.
This alert draws the PF's attention to the SPEED scale, and indicates the need to adjust thrust.
It comes immediately before the ALPHA Floor.
? If the angle-of-attack still increases and reaches ALPHA Floor threshold, the A/THR triggers
TOGA thrust and engages (unless in some cases of one engine-out).
In case of an emergency situation, such as Windshear or CFIT, the PF is assisted in order to optimize aircraft performance via the:
? A/THR: Adds thrust to maintain the speed above VLS
? Low energy warning "SPEED, SPEED, SPEED": Enhances PF awareness
? ALPHA FLOOR: Provides TOGA thrust
? HIGH AOA protection: Provides maximum aerodynamic lift
? Automatic speedbrake retraction: Minimizes drag.
OPERATIONAL RECOMMENDATIONS:
When flying at alpha max, the PF can make gentle turns, if necessary.
The PF must not deliberately fly the aircraft in alpha protection, except for brief periods, when maximum maneuvering speed is required.
If alpha protection is inadvertently entered, the PF must exit it as quickly as possible, by easing the sidestick forward to reduce the angle-of-attack, while simultaneously adding power (if alpha floor has not yet been activated, or has been cancelled). If alpha floor has been triggered, it must be cancelled with the instinctive disconnect pushbutton (on either thrust lever), as soon as a safe speed is resumed.
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