Flight Control System

Question 1

Describe the elevator system.

Answer 1

Conventional cables and pulleys system with no hydraulic assistance.

Question 2

How is the elevator system arranged?

Answer 2

Two seperate and independent cable systems. 1 connects the captain’s column to the left elevator, 2 connects the FO’s column to the left elevator. A torque tube located under the pilots feet is the only connection between the two systems.

Question 3

What is the function of the elevator disconnect?

Answer 3

It disconnects elevator system 1 and 2 at the torque tube.

Used if the elevator or cables become jammed. The side that is not jammed controls that sides elevator.

Question 4

How do you know if the elevator disconnect lever has been pulled?

Answer 4

The lever is out and a yellow elevator cautions light appears.

Question 5

How many elevator tabs are installed and what is their purpose?

Answer 5

An inner spring tab and an outer servo tab on each elevator.

To assist in moving the elevator when under aerodynamic load (not trim tabs).

Question 6

Describe the servo tab.

Answer 6

It is the outer of two tabs. Slaved to the elevator and moves proportionally opposite to the elevator to decrease the pilot input force. Operates continuously.

Question 7

Describe the spring tab.

Answer 7

It’s the inner of the two elevator tabs. It is rigged to move opposite to the elevator direction to decrease pilot input force. At low speeds it remains neutral. At high speed it functions to assist elevator movement.

Question 8

How is the autopilot and stick pusher incorporated into the system?

Answer 8

Attached to the captain’s side system.
If the elevator disconnect is pulled, and the captain’s side is jammed, the autopilot and stick pusher are not available.

Question 9

Describe the pitch trim system.

Answer 9

Pitch trim is achieved by an electrically actuated moveable horizontal stabiliser. Pitch trim signals are sent to the Horizontal Stabiliser Control Unit (HSCU) manually or automatically, and the HSCU commands (one of two) electric motors in the Horizontal Stabiliser Actuator (HSA).

Question 10

How does the HSCU control the trimming rate?

Answer 10

Based on the airspeed. Trim rate decreases as speed increases.

Question 11

What is the Horizontal Stabiliser Control Unit?

Answer 11

It is the brains of the pitch control system.
There are two channels.
The main channel receives input from the yoke and autopilot.
The second channel receives input from the pedestal switches.

Question 12

What is the Horizontal Stabiliser Actuator (HSA)?

Answer 12

It moves the stabiliser.
It consists of an electromechanical actuator and two DC motors.
The HSCU main channel drives motor 1 and the backup channel drives motor 2.
Only one motor operates at a time.

Question 13

Describe the pitch trim switches.

Answer 13

They are split switches. Both must be moved for the system to activate.

Question 14

What is the priority given to the trim switches?

Answer 14

LH switch over rides RH switch.
No set priority is given to the main (LH RH) switches over the pedestal switches, whichever is pressed first is given priority.

Question 15

What happens if both parts of the pitch trim switch are pushed for more than 3 seconds?

Answer 15

The trim will only be active for 3 seconds, continual pressing will not keep the trim active. After 3 seconds an aural alert is provided to prompt a release and re engagement if further trim is required.

Question 16

What happens if one half of the trim split switch is pressed?

Answer 16

Nothing. However if it is pressed for longer than 7 seconds, the system will recognise the switch has failed stuck in that position and disregard further input from that switch.

Question 17

Why should the pilot keep the aircraft in trim, especially after take-off?

Answer 17

To avoid excessive loads on the HSA. Excessive loads on the horizontal stabiliser may stall the HSA, resulting in a temporary loss of pitch trim command.

Question 18

What happens if the HSA is stalled?

Answer 18

The pitch trim will not activate. Pressing the trim switches for longer than 16 seconds in this condition will disable inputs from that channel.

Question 19

In what circumstance will the autopilot automatically control pitch trim?

Answer 19

When engaged.

When deploying or stowing speed brakes.

Question 20

Describe the roll control system.

Answer 20

Roll control is provided by hydraulically actuated ailerons.

There are two systems, connected by a torque tube at the pilots feet.

Question 21

How is aileron system 1 rigged?

Answer 21

The LH yoke is connected via cables and pulleys to the LH aileron hydraulic actuator.
This system also contains the autopilot servo.

Question 22

How is aileron system 2 rigged?

Answer 22

RH yoke via cables to the RH aileron hydraulic actuator.

This system contains the artificial feel unit (AFU) and the roll trim actuator.

Question 23

What is the purpose of the aileron Artificial Feel Unit (AFU)?

Answer 23

Designed to give pilots an aerodynamic load feedback.

Question 24

What is the purpose of the roll trim actuator?

Answer 24

It relocates the aileron neutral position.

There is no trim tab.

Question 25

How does each system control the ailerons?

Answer 25

The left and right systems are both capable of controlling both ailerons. Left is system 1, right is system 2.

Question 26

What happens to the aileron system if hydraulic fluid is lost?

Answer 26

Mechanical reversion mode comes in whereby the cables and connection through the torque link control aileron movement.

Question 27

What happens if aileron or rudder trim is depressed for longer than 3 seconds?

Answer 27

The trim will cutout, with no audible tone.

Question 28

What happens is an aileron is jammed?

Answer 28

Pull the aileron disconnect.
The unjammed aileron will provide roll.
Aileron disconnect is observed by a light.

Question 29

Describe the rudder system.

Answer 29

A dual, in-tandem system. The forward rudder is driven by the control system and the aft rudder is deflected as a function of the forward rudder.