AIRPLANE
OPERATIONS
MANUAL
CREW
AWARENESS
REVISION 39
2-04-25
Page
1
Code
01
AOM-145/1114
STALL PROTECTION SYSTEM
GENERAL
To help detect imminent stalls and to avoid stalling the airplane, the
EMB-145 is provided with a Stall Protection System (SPS). The SPS is
composed of one computer box with two independent channels, the
SPS panel, two Angle of Attack (AOA) sensors, two stick shaker
actuators, and one stick pusher actuator. The system provides
sensitive, visual and aural indications of an impending stall. To avoid
spurious actuation, the SPS receives signals from many airplane
systems, thus correcting its set point according to flaps and landing
gear position, icing and windshear conditions and Mach number.
At higher altitudes, the stall protection system advances its set point to
cope with compressibility effects. Therefore, the stall is always defined
by the pusher activation, regardless of the altitude. The basic
difference between lower and higher levels is that at higher altitudes
the pusher and the shaker speeds are higher due to above mentioned
stall protection set point advance, preserving the stall margin.
INTERFACES
Each channel receives data from the following on-side airplane
systems: AHRS or IRS, ADC, flaps, landing gear, air/ground,
windshear detection, ice detection and radio altimeter. Each Stall
Protection Computer (SPC) channel receives information from its
associated AOA sensor and sends it to the opposite channel in order
to compensate side slip influence on angle of attack measurements. A
locked AOA sensor signal is not considered in stall calculations and in
this case the channel will be deactivated. If a stall condition is
imminent, the system first actuates the stick shaker and disengages
the autopilot. If no corrective action is taken and the airplane is on the
verge of entering a stall, the stick pusher is actuated, which pitches the
nose down. Simultaneously, a clacker is generated in the aural
warning system.
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