Aero Chapter 03, High AOA/Stall/Spin
T-45 Aerodynamics Student Workbook
Because the T-45 provides minimal stall warning by natural airframe buffet, an artificial stall warning is
installed. At 21.5 units angle of attack, about 10 kts above stall, the left rudder pedal vibrates and a tone
is heard in the headset to alert the pilot of an impending stall. The natural airframe buffet commences
only one to two KIAS above stall, clean, and only one KIAS above stall in the approach configuration
(Figure 57).
CLEAN STALL
In the clean configuration, there is little or no aerodynamic stall warning such as buffet or wing rock until
immediately prior (1-2 kts) to stall (Figure 57). In power-on stalls with cruise power set, an approximate
20 degrees noseup attitude is a secondary indication of impending stall. With idle power, the pitch attitude
is significantly less and might not be noticeable. Artificial stall warning comes on at 21.5 units AOA, about
4.5 units and 10 kts prior to stall. At less than one unit AOA prior to stall, expect a slight wing rock and
buffet. If the back stick is eased at this point, the T-45 will not stall. If the aft stick force is increased, an
uncommanded wing drop of 25-30 degrees occurs, accompanied by a mild pitch break which defines the
stall at about 26 units AOA clean. Due to the longitudinal stick gearing at near full aft stick travel, a small
amount of aft stick commands a large stabilator deflection, so the rate of stall onset occurs more rapidly.
APPROACH STALL
With the gear down and flaps/slats HALF or FULL, there is no noticeable increase in buffet during the
approach to stall until immediately prior to the stall. The first indication of stall is a slight longitudinal
instability at about 28 units AOA. At 29-30 units AOA, buffet increases noticeably, followed closely by an
uncommanded wing drop of 15-20 degrees and a pitch break that defines the stall. The indicated
airspeed may decrease only one knot from 28 units AOA to the stall (Figure 57). Release of aft stick
pressure at this point produces an immediate reduction in AOA and stall recovery. If aft stick is
maintained, the nose pitches down about 6 degrees. Speed brake position has no effect on stall
characteristics. Stall recovery is immediate upon the release of aft stick. Altitude loss is minimized by
applying MRT power and recovering at 24 units AOA.
STALLS WITH EXTERNAL STORES
Stall occurs about one unit AOA lower with external stores loaded. With wing store asymmetry, the T-45
rolls into the heavy wing and may require up to one-third lateral stick to maintain wings level on approach
to stall. Otherwise the characteristics with stores loaded are similar to the clean stall.
ARTIFICIAL STALL
STALL BUFFET
STALL
WARNING
CLEAN
21.5 Units / 10 KIAS
25 Units / 1-2 KIAS
26 Units / 0 KIAS
APPROACH
21.5 Units / 10 KIAS
28 Units / 1 KIAS
29-30 Units / 0 KIAS
NOTE: All Speeds Are KIAS Above Stall Speed
Figure 57: T-45 STALL CHARACTERISTICS
(7-99) Original
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