Aircraft: Exam Questions and Navigation Techniques

This document contains exam questions related to aircraft voice communication, navigation aids, radar, and more. It covers the features and characteristics of radio wave propagation and the 3-axis control of aircraft attitude. The document also explains the functional components of an aircraft weather radar system and the relationship between the peak power, mean power, and duty cycle of a primary radar system.

Aircraft
Exam questions
Institutional affiliation
Student name
Student ID Number
Professor (tutor)
Date of submission
1

Question 1
An aircraft voice communication system is a system that uses voice transmission over the
radio to control the aircraft aviators. It connects air traffic control to other voice transmission
technologies such as the radio, and the public switched telephone network, PSTN, and the
quality requirements set for the system are very strict.
Question 2
Navigation aids and techniques available for use in a typical civil aircraft
Navigation aids and techniques enable the movement of the civil aircraft by guiding the
direction they take while in flight mode:
(i) Radio altimeter measures the distance the aircraft is cruising at from the terrain
beneath it. It indicates the altitude of the typical civil aircraft. It provides a high level
of accuracy and response as compared to the air pressure altimeter which is used for
AGL information.
(ii) Weather radar is used to detect different types of weather conditions. There is an
onboard radar that gathers information from the surrounding about the weather
activity, a lightning detector, and a satellite or weather radar information source used
to upload information for access by the air traffic control team on the ground.
(iii) Emergency locator transmitter, ELT, usually detects the extreme G-forces that are
expressed when an aircraft is crashing. It is supported on battery mode and uses an
activated transmitter. The information on the aircraft location is uploaded to the
COSPAS-SARSAT satellite periodically.
2

(iv) The global positioning system is used in the aircraft to enable proper navigation, and
it links up with the NAVSTAR satellite. The GPS can send continuously coded
transmissions from the satellite which enables tracing the situation of an aircraft. The
wide area augmentation system is also developed to improve the efficiency of the
GPS system.
Question 3
Radar in air traffic control applications
The radar system uses an antenna to send and receive signals when it hits a target. It is
used in air traffic control applications to detect and distinguish an aircraft approaching the airport
or flying over a certain region of interest.
Question 4
Functional components of an aircraft weather radar system
(i) Onboard radar system used in identifying and displaying the weather activity and
condition.
(ii) Lighting detector used to observe lightning trends before and when they occur.
(iii) Satellite connection. It is used when the aircraft wishes to get information on weather
in regions to be approached as well as information uploaded by other aircrafts in the
region about the weather conditions.
3

Question 5
Closed loop feedback in automatic flight control systems
(i) It provides closed-loop system stability. It could, to some extent, provide some degree
of robustness that would be of practical advantage. The feedback loop makes the
system resilient towards external influences.
(ii) It provides fitting flying qualities obtained from low-level mathematical models that
are aligned to certain modes of flight. The feedback loop creates linearity in a system
that has a lot of non-linearities.
4

Question 6
Main features and characteristics of radio wave propagation at HF, VHF, and UHF.
Frequency band Frequency range Application
High Frequency (HF) 3-30 MHz Used in the long-distance
communication in aircraft and airships
Very High Frequency
(VHF)
30-300 MHz FM, television broadcasts, and aircraft
communications.
Ultra-High Frequency
(UHF)
300MHz-3GHz Navigation using GPS.
Broadcasting for television and
microwave links.
Wireless communication for ZigBee,
Bluetooth, cellphones, and wireless
LAN.
The HF, VHF, and UHF are terrestrial radio communication frequencies. The VHF and
UHF propagate based on the line of sight. Buildings and other terrestrial features block such
signals, but the reflections are useful in overcoming the obstructions. The signals may fade when
they are transmitted in multipath, and the condition is referred to as picket fencing. The
atmospheric inversions can cause VHF and UHF signals to travel long distances in the
tropospheric ducting mode. The UHF is more effective inside the building as compared to the
VHF as it has a shorter wavelength which allows easier penetration of the structure of the
buildings.
Question 7
(a) DSB AM and SSB
The double sideband transmits frequencies developed during the amplitude
modulation in a symmetrical and well-spaced format in the upper and lower regions of
the carrier frequency forming an envelope that carries the message signal on the carrier
signal. The BPSK mode is implemented in digital telemetry.
5

The single sideband modulation performs an amplitude modulation signal with
elements set up or removed. It can be implemented as the single sideband suppressed
carrier, the single sideband reduced carrier or the independent sideband. The SSB signal
is composed of the single sideband without a carrier signal.
(b) VOR and DME based navigation aids
The VHF omnidirectional range and the distance measuring equipment, make up
the radio triangulation station for the airplane that consist of two radio ideals. VOR
generates an viewpoint between the station and the receiver in the aircraft while the DME
produces the angle for the array.
(c) Gyroscope-based navigation
The navigation or orientation of the aircraft or airship concerning the earth is
determined by a gyroscope system that uses the earth’s gravity as the determining factor.
The gyroscope is composed of a rotor, a freely-rotating disk, that is mounted onto a
spindle in the middle of a greater and more stable wheel.
Question 8
The relationship between the peak power, mean power and duty cycle of a primary radar system
6

Duty cycle determines the percentage of time that a signal stays at a high level. Peak power
refers to the maximum power supplied by the system for transmission and reception. Mean
power or the average power is given as a ratio of the pulse width to the pulse repetition time.
P
Pi
= τ
T =duty cycle
P−average power∨mean power
τ − pulse width
T − pulse repetitiontime
Pi− pulse power
Question 9
3-axis control of aircraft attitude?
The roll, pitch, and yaw comprise the three-axis rotations that affect the stability of an
aircraft while in motion. It is important to find a way to control all the three. The rotation axis
that runs through the plane from front to back is the roll, the rotation axis that runs side-to-side is
the pitch while the yaw is the rotation axis line that runs on the vertical axis. This is carried out
such that,
Controller Control parameter
Rudder Yaw
Ailerons Roll
Elevators pitch
The function of the Yaw damper?
The yaw damper is implemented in aircraft to reduce the rolling and yawing fluctuations
in the Dutch-roll mode. It is made up of the yaw-rate sensors and a processor that delivers a
signal to the actuator that connects to a rudder.
7

8