11.9 Flashcards
What does manoeuvre load control reduce ?
Aeroelasticity
( minimises excessive tip bending by using the Ailerons and spoilers )
( moves centre of lift inboard )
( happens at high speed )
What does a gust load alleviation ( GLA ) reduce ?
Reduces effect of gust loads on aircraft by deflecting control surfaces.
Which flight controls surface is used during GLA ?
Ailerons
Which flight controls are used for MLC ?
Ailerons
What is placed on a control cable to prevent contact with the aircraft’s structure ?
Fair leads.
( also reduce vibration )
Why Is a guard placed on pulleys ?
To ensure control cable doesn’t jump off pulley if slackened
What can improper tension cause ?
OSS of control travel or damage to components
Whats the use for a tension regulator ?
Maintains cable tension when it’s subjected to expansion and contraction of the aircraft’s structure.
Whats the use of a bell crank ?
Change direction of force transmission.
When’s a torque tube used ?
When you want to covert a linear motion to rotational.
What do screw jacks convert ?
Rotary motion into linear.
( used for moving surfaces which experience extreme aerodynamic loads )
What does a hydraulic power control unit combine ?
Individual hydraulic components into an assembly
( position flight control surface in response to a command )
( protection against flutter )
How does hydraulic systems used for the flight controls help the pilots manoeuvre the plane ?
Assists flight crew to over come the aerodynamic forces encountered by the control surfaces to control the aircraft.
( allows aerodynamic load provide feedback feel to crew )
What are hydraulic power control units ( PCUs ) used for ?
To position primary or secondary flight control surfaces.
( single assembly that combines individual hydraulic components Into a assembly )
What is found in the heart of a PCU ?
Servo valve and actuator
Whats a servo control units 2 main operating modes ?
- control mode
- damping mode
When does a servo control unit enter the control/active mode ?
When hydraulic pressure supply is witched on.
( control valve moves in opposite direction to the mechanical input )
( hydraulic system is pressurised )
When is the servo control unit in damping mode ?
When the servo control unit is depressurised
( when on ground )
( PCU in damping mode to avoid flight control surfaces moving the control stick or yoke in gusts of wind )
( bypass valve is closed )
( actuators chambers are interconnected )
E.G - PRACTICE QUESTION —— In electrically controlled hydraulically operated flight control system (FBW) , after total electrical failure can we move the control surface ?
No
E.G. PRACTICE QUESTION —— in a FBW system, after total hydraulic failure, what are the control surfaces still available to be used ?
None !!!!!!!
What emergency systems are powered by pneumatic as a backup ?
Emergency lowering of landing gear, brakes, nose wheel steering.
( pneumatic not used in flight for normal controls as air is compressible )
Why would you use an artificial feel unit ?
As in hydraulic transmission , the crew cannot feel the effect of the air-load and because of this a feel unit. Is installed providing an artificial feel of the air-load.
( artificial air-load provided is smaller than actual air-load making it easier for crew to. Control )
How is the artificial air-load placed on control surface ?
Using a spring
Whats an advantage of FBW ?
Weight saving
What does the 3 gyroscopes fitted in aircraft sense ?
Movement changes in 3 main control surfaces.
Whats pre flight FBW tester is used ?
Built in test equipment ( BITE )
Whats a fly-by-wire control modes purpose ?
Transforms movement from joystick made by crew into movements of aircraft control surfaces.
Whats the two laws a primary flight computer can perform under ?
— Normal law - differs depending on stage of flight.
— Alternate law.
Explain the term fly-by-wireless network ?
Reduction in the weight of aircraft by removing extensive bundle of wires used in fly-by-wire aircraft.
Whats an advantage of the fly-by-wireless network ?
Reduced maintenance
Weight saving
In flight, what the purpose of a yaw damper ?
Counters the rolling tendency of aircraft during flight ( Dutch roll )
( engaged by switch on the flight control module )
Where does the aerodynamic centre on the wing move ?
Aft ( trailing edge )
Whats Mach trim used for ?
As aerodynamic centre moves towards rear of wing as the aircraft transitions through the transonic region, it forces a nose down attitude ( Mach tuck ) which Mach trim is used to counteract.
What is rudder limiter ?
Rudders movement is limited to aircraft’s speed due to the high loads absorbed by the large control surface
( adds extra weight )
Whats static balancing ?
An object remaining stationary when supported by its centre of gravity.
2 ways it can be out of static balance :
Under balance +
Over balance -
What is dynamic balancing ?
Balanced rotating forces so that no vibration is produced while the body is in motion.
Where about does the weight of a control surface increase after repairs ?
Aft of hinge line.
Whats the three methods to rebalancing control surfaces ?
- Balance beam - removed and placed on trestle
- Scale -surface removed and placed on trestle
- Calculation - surface till attached to aircraft
Whats aircraft rigging ?
Adjustment and travel of the moveable flight control surfaces that are attached to major structures.
( aligning the neutral position of the control surface to the control column. )
Why are rigging pins used ?
To set control system into neutral position.
What two angles determine the pitch attitude protection ?
Angle between longitudinal axis to horizon
What is staling ?
Flow separation over the wings.
