Avionics MCQs – Fly-By-Wire Technology – 1

1 - Question

Why is the BFW system used?
a) To control aerodynamically efficient but unstable body
b) For communications in aircraft
c) Better navigation
d) Reduced chances of enemy detection
View Answer Answer: a
Explanation: The literal meaning of Fly By wire system is flying by wires(I.e; electrically). One of the main advantages of using FBW is to exploit increased aerodynamic shapes at the cost of stability. The FBW system provides high integrity automatic stabilization to compensate for the loss of stability and provide overall better performance.

2 - Question

How is fly by wire system implemented in an aircraft?
a) By using control rods and linkages connecting stick to control surfaces
b) By using high power radio transmitters and receivers
c) By using computers and actuators to control surfaces
d) Artificial intelligence
View Answer Answer: c
Explanation: The fly by wire system uses actuators to move the control surfaces to maintain the stability of an aircraft. The signals sent by the pilot via the control stick is intercepted by the flight controller computer and signals are sent to the respective actuators to move the control surfaces.

3 - Question

Which one of the following is not true with respect to the FBW system?
a) FBW is not necessary for every aircraft
b) FBW makes an aircraft stealthy
c) FBW provides better control and carefree flying
d) FBW makes aircraft with low stability fly smoothly
View Answer Answer: b
Explanation: The FBW system need not necessarily provide stealth to an aircraft. It provides control, stability and carefree flying in aircraft with low natural stability. Typically stealthy aircraft design is mainly focused on stealth and has very less stability, here FBW provides good handling and control characteristics to fly the aircraft without FBW system.

4 - Question

Which of the following is not a component of the FBW system?
a) Flight control computer
b) Aircraft motion sensor
c) Actuators
d) Communication receivers
View Answer Answer: d
Explanation: The fly by wire system consists of control stick (input by the pilot), Flight control computer(processing unit), actuator control electronics(signal to actuators), actuator(movement of control surfaces). Communication systems are completely independent of FBW systems.

5 - Question

FBW system requires an air data system for control and stability.
a) True
b) False
View Answer Answer: a
Explanation: The air data system provides various information like airspeed, height(density of air), angle of attack and temperature. These parameters change with flight and are considered necessary to maintain optimal control and stability at all times.

6 - Question

How are FBW signals transmitted?
a) Simplex
b) Duplex
c) Time division multiplexing
d) Code division multiplexing
View Answer Answer: c
Explanation: Transmission of electric signals is a key element in a FBW system. Faster the signal transmission, quicker the response of the aircraft to the pilot stick controls. Time division multiplexing is used where signals can be transmitted along a network comprising only of two wires as only one set of data is being transmitted at any particular time.

7 - Question

Which one of the following is a military standard data bus?
a) Mil Std 1553
b) ARINC 629
c) ARINC 429
d) COMAC C919
View Answer Answer: a
Explanation: Mil Std 1553 is a US military standard data bus which came out in the 1970s in the F-16 and the following models of fighter aircraft. It has a data rate of 1Mbit/sec and a word length of 20 bits to encode clock, data, and address and so can receive or transmit up to 50,000 data words a second.

8 - Question

What type of cable is used in ARINC 629?
a) Coaxial cable
b) Screened twisted pair
c) Unscreened twisted pair
d) Parallel lines
View Answer Answer: c
Explanation: The ARINC 629 links and bus uses an unscreened twisted pair of wires with a connection to the bus through demountable current transformer couplers. Mil STD 1553 uses screened twisted pair cables. Parallel lines are rarely used today.

9 - Question

Why are actuators used in FBW systems?
a) Movement of control surfaces
b) Reduce drag
c) Increase lift
d) Safety equipment
View Answer Answer: a
Explanation: Unlike traditional aircraft, FBW system uses electrical signals to operate the actuators which in turn move the control surface in place of mechanical linkages and control rods directly connecting the pilot’s stick to the control surfaces.

10 - Question

Why are both electrical and hydraulic systems are used in the same aircraft?
a) To generate more force
b) Quick deflections
c) As a fail safe
d) Hydraulics for more force and electric for quick deflections
View Answer Answer: c
Explanation: Most of the main actuators are electro-hydraulic, fully electric actuators are used as a fail safe for hydraulic actuators. They must be able to survive any two failures and carry on operating satisfactorily in order to meet the aircraft safety and integrity requirements.

11 - Question

The reason for using quadruplex actuation system is _______
a) precise movement
b) to counteract heavy air loads on the control surfaces
c) quick reaction to the control stick movement
d) as a fail safe mechanism
View Answer Answer: d
Explanation: A quadruplex actuation system consists of four independent actuators whose output drives the power control unit. The fail-safe mechanism of the quadruplex system is that when one fails three can override it. All four actuators have totally independent power and control electronics.

12 - Question

In a typical quadruplex actuator system, how is the failure of an actuator identified?
a) By comparing it with the signal of the three good ones
b) By comparing it with a simulation model
c) Using in-lane fault detection
d) Using reflectometry
View Answer Answer: a
Explanation: A typical quadruplex system uses signal processing based FDI( Fault Detection and Isolation) system. It identifies the failed actuator by comparing its control signal with the other three good ones. A model-based FDI system is generally used in triplex architecture.

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