FLIGHT CONTROLS 2

Question 1

What does Feel Diff Press light mean?

Answer 1

Kicks on when there is a loss of hydraulic system A or B
Or
By an elevator feel pitot system blocked or failed
Or
Activation of the elevator feel shift module
Or
Either left or right AOA is erroneously high

Question 2

What is the function of the Elevator Feel Shift Module?

Answer 2

Applies 4 times normal force on the elevators usining hyd system A pressure.

Question 3

Explain the Elevator Feel Shift Module system?

Answer 3

Normal Operation

During normal operation, there is no EFSM hydraulic output pressure to the dual feel actuator. The feel pressure is not changed by the EFSM. The EFSM receives 3000 psi nominal system A pressure. The pressure reducer provides 850 psi to the mode valve. The mode valve remains closed until SMYD 1 or SMYD 2 commands the dual coil solenoid valve to open during a stall.

EFSM Operation

At stall onset, either SMYD sends a signal to energize the dual coil solenoid valve on the EFSM. The EFSM operation occurs when all of these conditions occur:

• Stick shaker is active

• AOA is 8 to 11 degrees more than thermal anti-ice (TAI) biased stick shaker AOA

• EFSM is not inhibited due to low altitude or the airplane is on the ground.

When all of these conditions occur, the SMYDs energize the dual coil solenoid valve. The solenoid valve sends 3000 psi system A pressure to the pressure-operated mode valve.

The mode valve opens and sends pressure between 820 psi to 880 psi from the pressure reducer to the system A side of the dual feel actuator. This increases the control column feel forces up to four times nominal feel. The increased feel force makes sure the pilots cannot easily override automatic stabilizer movement to nose down pitch of the airplane.

Training Information Point

There is no flight deck annunciation that the EFSM is armed or operating during a stall.