Aero Chapter 03, High AOA/Stall/Spin
T-45 Aerodynamics Student Workbook
Above 21.5 units, the front cockpit AOA indicator triggers the artificial stall warning tone and left pedal
shaker. The front indicator inputs to both cockpit indexers and the approach lights on the nose gear. Due
to the different circuitry for the rear cockpit AOA indicator and indexer, an error in the system could cause
a different reading between the rear seat indexer and indicator.
The AOA indicator is useful in all phases of flight, while the AOA indexer is only illuminated when the
landing gear is down.
The indexers function similarly in both cockpits (Figure 63). The upper V indicates slow (18 units or
greater), the donut is optimum (17 units), and the indicates fast (16 units or less). The upper V and a
donut lighted simultaneously indicate a little slow (17.5 units). The and a donut indicate a little fast
AOA ON ADI DISPLAY (T-45C)
A digital AOA indication in tenths of units is displayed in the upper left portion on the T-45C ADI display
just below the barometric altitude (Figure 63). The AOA prefix is the symbol.
AOA ON HUD DISPLAY
The head-up display (HUD) also provides a digital indication of AOA on the left side of the HUD just below
the indicated airspeed . The AOA prefix is the symbol. The digital AOA is displayed all the time when
the landing gear is up.
When the landing gear is
down, the digital AOA is
displayed only when AOA is
more then 18 units or less
than 16 units (Figure 64).
An AOA bracket E (Figure
64) is displayed to the left of
the water line symbol on the
T-45A and the velocity
vector on the T-45C. The
E moves up and down with
AOA to indicate slow (high
on E) or fast (low on E).
On speed is when the HUD
indicator is on the middle
arm of the E.
On the T-45A, the AOA
bracket does not go past the
Figure 64: HUD AOA DISPLAY
water line symbol for AOA
more than 18 units or less
than 16 units. On the T-45C, the AOA bracket moves beyond the velocity vector when the AOA is more
than 18 units or less than 16 units.
When the AOA bracket reaches the edge of the HUD display, the digital AOA numbers will flash.
The approach lights are located on the nose landing gear strut (Figure 63) and provide the Landing Signal
Officer (LSO) an indication of the aircrafts speed. The green light indicates slow, the yellow light on-
speed, and the red light fast.