Flight Controls Flashcards
What computer is part of the Flight Control System and how is it powered?
The Flight Control Electronic Control Unit (FCECU) is a two channel unit power by the Left (Channel 1) and Right (Channel 2) Essential DC Buses. Both are powered by their respective DC essential buses.
Describe the elevators.
The Elevators are two mechanically controlled and hydraulically operated. The elevator is able to be split left and right and controlled independently by the yokes in case of a mechanically jamb.
Both primary hydraulic systems can power the elevator and the #3 Hydraulic system is the emergency back up in case of the failure of one or both of the primary hydraulic systems.
Which Elevator PCUs are linked to which system?
Outboard - #1
Center - #2
Inboard #3
How is the elevator gust locked?
A compensator on the #3 PCU return line maintains positive pressure on the PCU to prevent gust damage and also supplies flutter protection.
How is the elevator protected from damage in case of a PCU main control valve jamb?
Both elevator hydraulic circuits have input bungees to prevent PCU runaways if the control circuit jambs.
How is artificial feel provided?
Two Pitch Feel and Trim Units (PFTU) are located in the vertical stabilizer and provide feel and trim inputs to the elevator control system.
The FCECU commands two pitch feel actuators to extend or retract depending on inputs from the ADUs and AHRS.
Describe the pitch trim system.
The PFTUs are each equipped with an electrical pitch trim actuator. The FCECU controls the pitch trim rate (high or low speed) according to the airspeed of the airplane.
High speed trim is active below 180 KCAS.
Low speed trim is active above 180 KCAS.
Describe the rudder.
The rudder is mechanically controlled and hydraulically powered.
Both primary hydraulic systems power the rudder. The lower PCU is powered by system #1 and the upper by system #2.
The rudder has a fore section and an aft section. The aft section deflects twice as much as the forward section.
How much travel does the rudder have and is it constant?
If the flap lever is in the 0 position the forward rudder moves 12 degrees.
If the flap lever is any position other than 0 the forward rudder moves 18 degrees.
Is rudder authority always the same?
The FCECU reduces hydraulic pressure to the rudder as airspeed increases to limit yaw rate.
How is the rudder trimmed?
A two speed electrical rudder trim actuator which acts on the rudder trim/feel summing mechanism. The speeds are selectable on the trim switch.
How does the yaw damper operate?
The yaw damper uses a electrical actuator to supply automatic inputs to the summing mechanism to compensate for minor yaw oscillations.
It is limited to 4.5 degrees of movement and uses ADC data.
What indications will we have of a Rudder PCU jamb?
A RUD 1 or RUD 2 switchlight will illuminate if a mechanical jamb occurs in a PCU.
Describe the roll control system.
There are mechanically controlled and operated ailerons directly linked to the co-pilots control wheel and interconnected to the captain’s control wheel. These can be split in case of a mechanical jamb. The ailerons incorporate a geared tab which moves in the opposite direction of the control surface to aerodynamic assistance.
There are also mechanically controlled and hydraulically operated flight spoilers connected to the captain’s control wheel.
Describe the aileron trim system.
The Aileron Trim and Centering Unit transmits trim commands to the forward aileron quadrant to provide trim. The neutral position of the control wheel is automatically reset.
If a trim runaway occurs a travel limit switch automatically shuts off power to the trim actuator.
