Engineering Questions with Answers - Multiple Choice Questions

MCQs on Digital Implementation

1 - Question

How does the digital implementation in the FBW system reduce weight?
a) Lightweight materials
b) Fewer components
c) System integration
d) Automated control

View Answer

c
Explanation: In a typical Digital FBW system, One computer can control all three axes of control, whereas an analog system requires dedicated hardware for each axis of control. The reduction in hardware weight and volume, due to system integration, is of the order of 5:1 for a system of even modest complexity. The more complex systems could not be implemented economically using analogue technology.




2 - Question

Which of the following is not a result of digital implementation?
a) Hardware economy
b) Flexibility in updating
c) More power
d) Built in test capabilities

View Answer

c
Explanation: The digital implementation in FBW only affects the control and stability of the aircraft. Power is not, in any way, related to the FBW system.




3 - Question

What is it called when the sampled signal is of lower frequency than the original signal?
a) Aliasing
b) Overshoot
c) Steady state error
d) Damping

View Answer

a
Explanation: When the sampled signal is of lower frequency than the original signal it is known as aliasing. Aliasing induces data loss and errors. It can be reduced by a process called anti-aliasing.




4 - Question

How is aliasing prevented?
a) Sampling at the same frequency of the original signal
b) Sampling at double the frequency of the original signal
c) Sampling at less than double the frequency of the original signal
d) Sampling at more than double the frequency of the original signal

View Answer

d
Explanation: Aliasing occurs when the sampling rate is lower than the frequency of the original signal. The Nyquist theorem states that the sampling rate should be more than twice the frequency of the original signal to avoid aliasing.




5 - Question

How is data staleness overcome?
a) Time synchronisation
b) Down conversion
c) Up conversion
d) Using multiple channels

View Answer

a
Explanation: Data staleness problem it is necessary to have some form of time synchronisation of the computer iteration periods. This iteration period synchronisation is generally implemented through software.




6 - Question

Which of the following is not an advantage of using a digital data bus?
a) Self test
b) Multiplexing
c) less weight
d) Not affected by electromagnetic interference

View Answer

d
Explanation: Very large reductions in the weight of cabling are achieved by the use of multiplexed data transmission and data bus networks. High integrity data transmission can be achieved with very comprehensive self checking and data validation capabilities. However, they are heavily affected by electromagnetic interference.




7 - Question

What happens when the output of one channel is delayed by one iteration period before comparing with other channels in a quadruplex system?
a) Latency
b) Staleness
c) Aliasing
d) High noise

View Answer

b
Explanation: Data staleness occurs when a channel is delayed by, say, one iteration, before comparison with others. To overcome this problem it is necessary to have some form of time synchronisation of the computer iteration periods.




8 - Question

Which of the following is true with respect to the passive optical sensor?
a) Not affected by EMI
b) Does not require an electrical supply
c) Output from the sensor is an optical signal
d) Processing this signal does not require any electrical device

View Answer

d
Explanation: Passive optical sensors offers particular advantages as these sensors are not affected by EMI. Passive optical sensors are defined as sensors which do not require electrical supplies or any electronic processing at the sensor, the output of the sensor being an optical signal which is modulated by the quantity being measured. The processing of this optical signal is carried out by a separate electronic unit which is fully screened from EMI, the only connection between the sensor and the electronic unit being an optical fibre cable.

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