The function of the ailerons is to give the pilot and copilot control of the aircraft about the longitudinal axis during flight. Multi-function spoilers (MFSs) on each wing help the ailerons in this function. Movement of the pilot's or the copilot's control wheel causes the ailerons and MFSs to move. The two aileron control surfaces are attached to the outboard, trailing edges of the wings. The MFSs are installed in the top surface of the wings.

Inputs from the flight crew mechanically transmit to the ailerons through pushrods, pulleys and a continuous loop control-cable mechanism. There are no power control units in the aileron system. The electrically controlled MFSs get their inputs from the pilot's (LH) control wheel. In flight, the MFSs go up to help the aileron which goes up.

There is a roll disconnect mechanism if the aileron control circuit becomes mechanically locked. If this occurs, the pilot can disconnect the pilot control wheel from the aileron circuit and keep roll control through the MFSs. The ROLL SPOILERS push-button-annunciator (PBA) is found on the GND/ROLL SPOILERS control-panel. If the aileron control circuit is not locked but the pilot's control wheel is locked, the pilot must then push the ROLL SPOILERS PBA. This will give control of the ailerons to the copilot and stop the roll aid function of the multi-function spoilers.

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A control wheel is installed on the top of the pilot's and the copilot's control column. Each wheel is of the horn type and attaches to an input shaft which has splines.

The control wheel outboard handles each have a toggle switch, a pushbutton switch, and a radio transmit switch. The toggle switch is used to control the pitch and roll trim positions. The pushbutton is used as master switches to connect and disconnect the trim actuators, the autopilot, and the stick pusher at the same time. The radio transmit switch is used to start radio transmission and also to use the interphone.

The inboard handles also have two pushbutton switches which are used for autopilot synchronization and to change the page of the electronic check list.

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The roll disconnect mechanism is installed on the pilot's (LH) control wheel only. It has a lever, a shaft, a stud roller, a cam and two torsion springs. Two bushings align the lever and the shaft axially. During usual operation, the roller is pushed into the recess in the cam by the torsion springs. This makes the pilot's control wheel and the input quadrant turn as one unit.

The roll disconnect lever is immediately forward of the right handle on the pilot's control wheel. When the pilot operates the lever, the roller retracts from the cam recess and a spring-loaded hook holds the roller in the disconnected position. This procedure disconnects the pilot's control wheel from its input quadrant so that the control wheel can turn freely.

The aileron controls can be connected again in flight. The pilot must first raise a small locking lever which holds the disconnect lever in the disconnected position. While he holds the disconnect lever, the pilot aligns the roller so that it can go into the cam recess again. He then releases the disconnect lever, which locks the pilot's control wheel to the roll disconnect mechanism.

If the aileron control circuit becomes mechanically locked, then the pilot can disconnect his control wheel from the circuit. The control-wheel position sensor in the control wheel continues to give the pilot roll control through the multi-function spoilers.

A situation can occur when the aileron control circuit is not locked mechanically but the pilot's control wheel is locked. In this case, the pilot must then operate the disconnect mechanism to give control of the aircraft to the copilot.

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The roll disconnect microswitch is installed in the control-wheel roll-disconnect mechanism. It has a mechanical plunger which is in contact with the disconnect mechanism. If the pilot operates the disconnect mechanism, the switch provides a ground to the Spoiler Electronic Control Unit (SECU). The SECU then provides a signal to the data concentrator unit (DCU) to give indication on the EICAS that the aileron controls are disconnected.

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There are two aileron position sensors on the aircraft. Both sensors are the same size but the internally different. One is a dual-channel, Rotary variable Differential Transformer (RVDT) which is installed inboard of the left aileron hinge line. The other is a single-channel RVDT and it is installed in the same position on the right wing. Movement of each aileron causes linkage to move which turns the two sensors. The output signal from the sensors goes to the flight data recorder. The signal is also used by the DCU to show the angular positions of the ailerons on the flight controls synoptic display of the EICAS.

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Each aileron control surface has a balance geared-tab and a bent tab. The bent tab is permanently set in its position on the aileron trailing edge to keep the surface upfloat at high speeds to a minimum. The left aileron has a trim tab to decrease the aerodynamic load on the pilots' controls. An actuator installed inside the aileron operates the trim tab.

A 1.5 lb (0.68 kg) mass balance is installed in the aileron during the assembly. If it is necessary, more adjustable mass balance can be installed along the hinge. This mass balance will prevent flutter if there is a malfunction of an aileron control rod. This adjustable mass balance is attached to the spar with four bolts.

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A pushrod mechanism moves the balance geared-tab in the opposite direction to the aileron. The mechanism has a constant length pushrod connected at both ends to brackets. One bracket on the support fitting of the trailing edge of the wing and the other on the balance geared-tab.

This geared-tab can move a maximum of 20 degrees each side of the aileron chord line. It moves at a rate of 1.111 degrees for each degree of aileron movement.

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The roll damper engages with the roll damper quadrant through a square shaft. The roll damper quadrant is installed at the bottom of the each control column. This quadrant and the control wheel are connected by a closed-loop cable circuit. In usual operations, the roll damper transmits all of the pilot's and copilot's inputs. If a control cable in the fuselage breaks, the roll damper will limit the rate of control input to the ailerons and multi-function spoilers. In this way a dangerous flight condition is prevented.

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The two force sensors are installed on the left and right force sensor quadrants below the flight compartment floor. They monitor the input forces from the pilot and copilot to the aileron control system. The output signals from the two sensors are sent to the flight data recorder through the data concentrator unit.

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A dual-channel sensor (which is an RVDT) is installed in the pilot's and the copilot's control wheel. The function of these sensors is to transmit control wheel position signals to the multi-function spoilers and to the flight data recorder.

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Left and right movement of each control wheel in the flight compartment moves the input quadrant on the control wheel input shaft. The control wheels are mounted on low friction bearings and they have a maximum travel of 110 degrees in each direction. Secondary stops in the control column, which are not adjustable, limit this travel.

The single-loop cable system continues to the drive quadrants in the main wheel wells at FS635.65. A pushrod connects the two drive quadrants together.

The output from these drive quadrants is connected to the outboard quadrants through symmetrical cable circuits in the left and right wings. A bell crank on each outboard quadrant moves the applicable aileron control surface through control rods. The range of aileron travel is 18 degrees up or down.

The autopilot servo connects to the right drive quadrant through closed-loop cables. It controls the aileron system when the autopilot is engaged. The aileron trim indication is shown on the primary page of the EICAS display.

The aileron position indication is shown on the FLIGHT CONTROLS synoptic display on the EICAS status page. This display shows the aileron movements in the up or down positions on a scale with pointers. The pointers show the aileron position from full up to full down with a mark on the scale in the neutral position.

A condition can occur when the aileron control circuit could becomes mechanically locked. If this occurs, then the pilot can disconnect the control wheel from the circuit by the operation of the roll disconnect lever.

A condition can also occur when the aileron control circuit is not locked mechanically but the pilot's control wheel is locked. In this case, the pilot must then operate the roll disconnect lever to give control of the aircraft to the copilot.

In the two conditions after the operation of the roll disconnect lever, the roll disconnect microswitch senses the retraction of the stud roller. The roll disconnect microswitch then sends a signal to the SECU which through the DCU will:

• Send a signal to the EICAS display if the aircraft is on the ground (only) and in the take-off configuration. Then the ROLL DISCONNECT warning message will show


• Send a signal to the EICAS display if the aircraft is in the air or on the ground and not in the take-off configuration. Then the ROLL DISCONNECT status message will show.

The EICAS messages that follow are related to the aileron control system:

EICAS MESSAGE(S)	LEVEL (COLOR)
ROLL DISCONNECT	WARNING (red)
ROLL DISCONNECT	STATUS (white)

 

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
-	CONTROL WHEEL (LH)	ZONE(S) 211	27-11-01
-	CONTROL WHEEL (RH)	ZONE(S) 212	27-11-01
-	ROLL DISCONNECT MECHANISM	ZONE(S) 211	27-11-05
S114	ROLL DISCONNECT MICROSWITCH	ZONE(S) 211	27-11-09
MPE45	AILERON POSITION SENSOR (LH)	ZONE(S) 554	27-11-13
MPE46	AILERON POSITION SENSOR (RH)	ZONE(S) 654	27-11-13
-	AILERON CONTROL SURFACE (LH)	ZONE(S) 551	27-11-17
-	AILERON CONTROL SURFACE (RH)	ZONE(S) 651	27-11-17
-	AILERON BALANCE GEARED-TAB (LH)	ZONE(S) 553	27-11-21
-	AILERON BALANCE GEARED-TAB (RH)	ZONE(S) 653	27-11-21
-	ROLL DAMPER	ZONE(S) 211	27-11-25
MT111	ROLL FORCE SENSOR (LH)	ZONE(S) 141	27-11-29
MT112	ROLL FORCE SENSOR (RH)	ZONE(S) 142	27-11-29
MT125	CONTROL-WHEEL POSITION SENSOR (LH)	ZONE(S) 211	27-11-33
MT126	CONTROL-WHEEL POSITION SENSOR (RH)	ZONE(S) 212	27-11-33

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