Angle–of–Attack
There are two alpha vanes, one located on each side of the forward fuselage. The vanes
measure airplane angle–of–attack relative to the air mass.
Option - Angle of attack indicator
The primary source of data for the AOA indicator on the PFD is supplied by the ADIRU, with
the SMYD as the backup source. The source selection is automatic in the event of primary
source failure. Slight differences between the Captain’s and FO’s indications may be
noticed due to sideslip or vane installation errors. These differences could be as large as 2
degrees alpha.
Total Air Temperature
A total air temperature probe is mounted outside the airplane to sense air mass
temperature. The temperature sensed by the probe is used by the ADIRUs to compute total
air temperature.
Static Air Temperature
Static air temperature, displayed on the CDU PROGRESS page, comes from the ADIRUs,
using total air temperature probe information.
