Familiarization Flight Procedures
T-45C TS, ADV & IUT FamFP-01
D. HUD 126.96.36.199.1
Sg 4, fr 22
Digital AOA readouts on both the ADI and HUD are
displayed in units of AOA. By contrast, the velocity
vector on the HUD is referenced to a pitch ladder in
Sg 4, fr 23
Subtracting the HUD velocity vector pitch position on
the pitch ladder from the HUD waterline pitch angle,
results in the approximate AOA angle in degrees. That
number - degrees of AOA - will always be approxi-
mately 7-8 whole digits less than the AOA readout
displayed in units on both the HUD and ADI.
In the case exemplified in this lesson, AOA in degrees
is 15, whereas AOA in units is 23. "Rotation" of the
HUD pitch ladder has occurred, because the velocity
vector is vertically "limited." That happens whenever
the AOA angle exceeds approximately 11.1 degrees.
Then, any further increase in AOA results in the pitch
ladder rotating around the flashing velocity vector
positioned at the bottom of the HUD, so the velocity
vector will always indicate degrees of pitch accurately.
However, pitch ladder rotation causes the HUD water-
line pitch indication to be inaccurate. Also, note under
such conditions, waterline pitch indications on the ADI
and HUD will be at variance; the ADI waterline pitch will
be accurate; the HUD waterline pitch will be inaccurate.