Stall Warning System; Stall Warning Indications - BOMBARDIER LEARJET 40 Pilot's Manual

Pilot's Manual

STALL WARNING SYSTEM

The stall warning system, also referred to as the Angle-of-Attack
(AOA) system, is installed to provide the crew with an indication of im-
pending airplane stall. The stall warning system consists of two inde-
pendent systems which use a dual channel computer.
Other system components include two AOA sensors, control column
shaker motors and an interface with the PFDs. Left and right AOA in-
dicators are available as an option. Each channel of the computer gen-
erates a reference signal to the corresponding stall vane and, in return,
receives AOA information. The computer then processes this informa-
tion with airspeed, altitude, flap setting, and weight-on-wheels inputs
to determine the stall warning indications. The left and right stall warn-
ing systems are powered from the left and right essential buses respec-
tively. The circuits are protected by the L STALL WARN and R STALL
WARN circuit breakers located on the pilot's and copilot's circuit
breaker panels (FLIGHT group).

STALL WARNING INDICATIONS

As the airplane approaches stall speed, stall warning indications are ac-
tivated. The shaker speed will be above the stall speed at the most crit-
ical weight and Center of Gravity (CG). The stall warning computer
sums inputs of AOA and altitude shift along with flap position from
the flap position indication unit. Stall warning is biased for each flap
setting. The stall warning system provides the following aural, tactile,
and visual indications when the predetermined conditions have been
reached:
(1) The left and right channels of the computer drive low-
speed cues on the pilot's and copilot's PFDs respec-
tively. The low-speed cue is a vertical red bar on the
inside of the airspeed tape which rises from the bottom
of the tape as the airplane AOA increases. The point at
which the red bar reaches the airspeed pointer will
coincide with the point at which other stall warning
indications are activated.
(2) The left and right channels of the stall computer will
activate the control column shaker motors.
(3) The non-cancelable voice message "STALL" will repeat
until the AOA is decreased.
(4) The AOA indicators (if installed) will enter the red
band on the indicator.
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