757
MAINTENANCE MANUAL
ELEVATOR FEEL
COMPUTER
SEE A
SEE B
RIG PIN HOLE E/ST11
FEEL COMPUTER
CONTROL ROD TO THE HORIZONTAL STABILIZER
AFT
AUXILIARY PITOT SYSTEM NO. 2 PRESSURE LINE
STATIC LINESTATIC LINE AUXILIARY PITOT SYSTEM NO. 1 PRESSURE LINE
ELEVATOR FEEL COMPUTER
A
Elevator Control System Components
Figure 6 (Sheet 1)
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A
757
MAINTENANCE MANUAL
SLAVING
SEE C
ROD
FWD
OUTBOARD MIDDLE CONTROL INBOARD PCA INPUT ELEVATOR
PCA PCA ROD PCA CONTROL ROD POSITION
TRANSMITTER
LEFT SIDE POWER CONTROL ACTUATORS SHOWN
(RIGHT SIDE SAME)
B
INPUT CRANK SUPPORT SLAVING
RIG PIN E/ST8 HOLE SHOWN
ROD (RIG PIN E/ST9 HOLE SAME)
CONTROL ROD
INPUT CRANK
CONTROL
CENTERING SPRING ROD
POWER SUPPORT CLIP
CONTROL
ACTUATOR (PCA)
INPUT POGO ROD FWD
SUMMING LEVER
LEFT SIDE MIDDLE PCA SHOWN (RIGHT SIDE SAME)
C
Elevator Control System Components
Figure 6 (Sheet 2)
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A
757
MAINTENANCE MANUAL
I. Neutral Shift and Override Mechanism (Fig. 5)
(1)
The neutral shift and override mechanism is installed on the aft mechanism torque box. The neutral shift mechanism is connected by control rods to the feel unit and stabilizer. The feel unit is reacted to ground on the horizontal stabilizer through an override in the neutral shift mechanism. This allows the stabilizer trim to introduce elevator neutral shift in the airplane nose down direction when the stabilizer is trimmed in the 0.0 to 4.0 unit range. The override in the neutral shift mechanism allows the control system to override the feel unit in the event of a jam in the feel actuator.
J.
Asymmetry Limiter Actuator (Fig. 5)
(1)
The linear actuator consists of a 28 volt dc reversible motor that drives an acme screw to extend and retract a ram. The motor assembly has a magnetic coil-operated disc brake that engages when the motor is de-energized. Extend and retract limit positions of the ram are controlled by electrical switches located under the switch cover. The asymmetry limiter actuator limits the maximum possible commanded elevator motion by limiting the travel between aft quadrants. The system is operational full time but is used only following a left or right elevator control jam. Asymmetry is limited to 24 degrees of elevator at low speeds and 8 degrees at high speeds. The actuator is installed on the first officer's aft quadrant.
K.
Elevator Pressure Reducer and Bypass Valves (Fig. 7)
(1)
One elevator pressure reducing valve is connected to each hydraulic system (L, R, C) and to the flight quadrant. The valves reduce hydraulic inlet pressure to a preset specified outlet pressure. A pressure bypass valve is operated by pressure from the right hydraulic system and is connected to the left hydraulic system. If the right system pressure is lost, the bypass valve will bypass the left pressure reducer and provide full left system pressure to the left system PCU.
(2)
The pressure reducers and bypass valves are located on the forward side of the APU firewall.
3. Operation
_________
A. Functional Description (Fig. 8)
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