A320 BUSS Vs Backup SPEED SCALE & AUTO PILOT ENHANCEMENT

Objective :

• Enhance crew awareness
• Crew workload alleviation
• More guidance in unusual situations

BUSS : IS USED TO FLY THE AIRCRAFT IN UNRELIABLE AIRSPEED SITUATION BELOW FL 250FT.

BUSS: information is based on a lift equation which uses the data provided by :

• Angle of attack
• slats/flaps configuration
• load factor
• weight
• backup characteristic speeds
• altitude is backed-up by GPS altitude

NOTE :

* BUSS IS REVERSIBLE .

*Vertical speed indication is not displayed when BUSS switch is turned on .

*once the buss is turned on, only on one PFD do not use the AP or FDs.

BUCKUP SPEED SCALE ENHANCEMENT AND AIRSPEED MONITORING :

In addition to the BUSS information which is based on the lift equation and the data provided by :

• Angle of attack AOA
• slats/flaps
• load factor
• weight
• backup characteristic speeds
• altitude is backed up by GPS altitude

The new speed scale also features:

• backup Mach number
• backup Vertical speed indicator on the PFD
• the green band is replaced by the speed indicator and the speed trend arrow .

AIRSPEED MONITORING :

The system is based on 3 ADR sources and 1 backup source , provided by the associated ECAM alert that shows the speed status , speed scale flagged on the PFD , action requires for quick reconfiguration , system limitation and sum-up in status page .

airspeed loss is not definitive , airspeed can be re-validated and recovered, airspeed is confirmed as valid by comparing it with the independent source .

All of the monitoring principles are based on ECAM actions ( no more QRH ) except only in one remote case where the QRH procedure is applied ( ALL SPD UNCERTAIN OR ALL ADR SPD UNCERTAIN OR BACK SPD UNCERTAIN ) .

^{AUTO PILOT ENHANCMENT}

The main idea of AUTO PILOT enhancement is to alleviate the crew workload and to increase the aircraft controllability as redundant system .

this enhancement introduces two new auto-pilot modes besides the normal AP function in the normal mode :

1- ALTERNATE AP MODE

2- BACKUP AP MODE

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If the system detects an unreliable airspeed, the autopilot will remain active, how ever it will go into auto pilot protection mode, and an FMA AMBER MESSAGE (AP IN PROT ) will appear on the PFD to alert the flight crew that the AP guidance is not followed .

AUTO-PILOT is resilient to Unreliable speeding, and comes with a full Automatic AP reversion and re-validation. Auto-pilot can be maintained regardless of the speed status and full advantage of the new speed monitoring function .

SPEED MONITORING AND AUTO-PILOTS MODE :

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