In the AF447, Thread #6, there was considerable discussions regarding unreliable air speed and AoA. There was a post by A33Zab that provided the following information regarding the Airbus BUSS design. It is standard on the A-380 and optional on other Airbus aircraft such as the A-330.
BUSS DESIGN
The BUSS is displayed on both PFDs. It is based on Angle Of Attack (AOA) information, and
enables to easily and safely fly the aircraft without any valid airspeed indication. The BUSS
enables to fly the aircraft in the entire flight domain while observing the design limits.
The BUSS scale is divided in three color-coded areas:
• In the green area, the aircraft has normal margin towards ultimate limits i.e. VMO/VFE for
upper limit and stall for lower limit
• In the upper and lower amber areas, the aircraft has limited margin towards ultimate limits.
Flying in the amber area is acceptable for a limited period of time but it should be avoided
• The red areas (FAST or SLOW) must be avoided.
The BUSS is tuned using the aircraft’s aerodynamic model with speed brakes retracted.
When the BUSS is active:
‐ The altitude indications are based on GPS data. Two amber dashes cover the last two
digits because the GPS altitude is less accurate than the barometric altitude
‐ The vertical speed indication is no longer available.
FLYING TECHNIQUE
The PF adjusts the pitch and thrust, to maintain the AOA in the green area of the speed
scale.
For approach, the flight crew should perform a stabilized approach.
The flight crew should change the aircraft configuration with wings level.