Aero Chapter 03, High AOA/Stall/Spin
T-45 Aerodynamics Student Workbook
ACCELERATED STALLS
An accelerated stall is one in which the aircraft stalls while under g loading. Accelerated stall warning
depends upon the airspeed and altitude. At higher altitude, the buffet begins mild and increases to heavy
at the stall. As altitude decreases and airspeed increases, the magnitude of the initial buffet increases
and the buffet band compresses, and at low altitude and high speed, there is very little buffet and warning
at the stall. Stall AOA decreases as Mach increases. The stall itself is indicated as a pitch oscillation
(bucking motion) that is noticeable at AOA anywhere between buffet offset, which is essentially where
maximum lift occurs, and full aft stick. Bucking, which is caused by the T-45’s stabilator stalling, is
accompanied by wing rock at all airspeeds. Easing aft stick is all that is required to recover.
It is difficult to obtain an accelerated stall in the approach configuration because nearly full aft stick with
high stick forces is necessary. The T-45 may wallow laterally near stall and the pilot may induce wing
rock. Recovery is immediate with relaxation of back stick. Rudder is effective in controlling the roll/yaw
oscillations following the stall.
STALL RECOVERY
In all configurations, stall recovery is immediate upon the release of aft stick (Figure 58).
OUT OF CONTROLLED FLIGHT (OCF)
DEPARTURE
In a departure, the aircraft produces an asymmetric amount of lift and drag, causing an abrupt pitch, roll,
and yaw. The departure may lead to a post-stall gyration if controls are not neutralized. The proper
recovery technique from a departure is to neutralize the controls (Figure 58).
POST-STALL
GYRATION (PSG)
PHASE
COCKPIT INDICATIONS
Control inputs during a
ENTRY
Normal Flight
departure may aggravate
INPUT
the situation, producing
post-stall gyrations.
REDUCE
During PSG, pilots will
AOA above stall
STALL
STICK FORCE
probably encounter
extremely high sideslip
INDUCED YAW
angles. These high
NEUTRAL
Aircraft no longer responds to
DEPARTURE
sideslip angles will likely
control inputs
CONTROLS
force the unpowered
rudder to full deflection.
NEUTRAL
POST - STALL AOA turn needle,
The pilot may need to
GYRATIONS and airspeed oscillation
apply considerable force
CONTROLS
on one rudder pedal to
SUSTAINED YAW
center the rudder. The
AOA and turn needle
INCIPIENT
proper recovery
pegged; airspeed oscillation
SPIN
ANTI - SPIN
technique from a PSG is
STEADY -
AOA and turn needle
to neutralize the controls
CONTROLS
STATE
pegged; airspeed steady or
(Figure 58).
SPIN
oscillating slightly
Figure 58: STALL PROGRESSION DIAGRAM
Page 34
(7-99) Original
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