Assignment – 1

Subject – Avionics

Submitted by: Submitted to:

Pramod Kumar Yadav Mr. Anshul Bansal
Roll no – 16/206 Assistant Professor
Batch – A2 Aeronautical Engineering
UTD, RTU KOTA
Q.1 (a) List the components of “Head Up Display” (HUD)?

Ans. - A HUD - Head Up Display - is a means of presenting information to the pilot in the line
of their external forward vision which projects key flight instrument data onto a small ‘see-
through’ screen positioned just in front of the pilot line of sight looking ahead out of the aircraft.

following components of HUD are.

 A computer to receive aircraft data and generate display symbology.

 An overhead unit to mount the cathode ray tube (CRT) which projects the assembled image
onto the transparent display screen in front of the pilot.
 The transparent display screen - called a combiner - which is a ‘holographic optical element’
made of glass or plastic that reflects the projected image towards the pilot’s eyes without
interfering with the passage of ambient light.
 A control panel to allow selection by the pilot of various display options and to enter data
not received and integrated by the computer from aircraft sensors.
 An annunciator panel to provide HUD status and warning information.

Q.1 (b) List the limitations of VHF communications against HF communications system?

Ans. – Limitations of VHF and HF

a. Point-to-point radio communications in the very high frequency (VHF) band (30 to 300
MHz) and UHF band (300 to 3,000 MHz) may be accomplished by two basically different
techniques. The first technique uses numerous repeaters or radio relays spaced at or near
the optical horizon. These systems are referred to as LOS systems. Where VHF is
employed, the relays may be somewhat beyond the optical horizon (that is, "fringe area")
due to refraction of VHF signals in the atmosphere. Because both VHF and UHF are
essentially LOS systems, the transmission path loss is relatively small and low transmission
power provides satisfactory communication.

b. While having many advantages over HF, the LOS systems do have limitations. Neither
LOS nor tropospheric scatter propagation is capable of spanning a large body of water
where lack of islands prohibits the installation of repeater stations, and ionospheric scatter
is too limited in bandwidth to provide more than a fraction of the service needed for the
DCS. HF radio has therefore furnished our major overseas long-distance links for years.

c. Terminal and repeater stations are vulnerable to both attack and sabotage. The
vulnerability of LOS systems is particularly great because of the large number of repeaters

d. Jamming is possible with only moderate effort. Ground-based or airborne jammers can jam
the side lobes of LOS receiving antennas or tropospheric scatter receiving antennas.

Q.2 – Discuss the importance and role of Avionics in modern aircraft?

Ans. – Role of Avionic
  Avionics = Aviation + Electronics
 Used in USA in early 1950s
 Any system in the aircraft, which is dependent on electronics for its operation is known as
avionics. Example
Fly by wire control system- it replaces the conventional manual flight controls of an aircraft with
an electronic interface.

Pilot control stick sensor assembly

Air Data Sensors

Gyroscope- is a device that uses earth’s gravity to help determine orientation, its design consists
of a freely rotating disk called a rotor, mounted onto a spinning axis in the center of a larger and
more stable wheel.

Accelerometer - An Accelerometer is a compact device designed to measure non-gravitational

acceleration. When the object it’s integrated into goes from a standstill to any velocity, the
accelerometer is designed to respond to the vibrations associated with such movement. It uses
microscopic crystals that go under stress when vibrations occur, and from that stress voltage is
generated to create a reading on any acceleration. Accelerometers are important components to
devices that track fitness and other measurements in the quantified self-movement.
Electro-hydraulic actuators - An actuator is a type of motor that is responsible for moving or
controlling a mechanism or system. It is operated by a source of energy, typically electric current,
hydraulic fluid pressure, or pneumatic pressure, and converts that energy into motion.
Importance of Avionics -
As we know that millions of dollar business is done by avionics industries, 30% of total cost of
the aircraft is beard by avionics equipment’s. This data is 40% for maritime, patrol, and anti-
submarine aircraft and 75% for Airborne early warning aircrafts.
The avionics systems are essential to enable the flight crew to carry out the aircraft mission safely
and efficiently.
Mission of aircraft is to carry the passengers to their destination and in case of military fighter
aircraft this can be intercepting a hostile aircraft, attacking a ground target, reconnaissance and
maritime patrol.
In military operations, reconnaissance is the exploration outside an area occupied by friendly
forces to gain information about natural features and enemy presence.
By automation of tasks, the crew (which consists first pilot/captain and second pilot) workload can
be reduced.
The reduction in weight is also significant and can be translated into more passengers or longer
range on less fuel.
The elimination of second crew member (navigator/observer/radar operator) has also significant
benefits in terms of reduction in training costs
Hence goals of avionics systems are
 Increasing safety
 Fulfilling air traffic control requirements
 Enabling all weather operations
 Reduction in fuel consumption
 Improved aircraft performance and control
 Handling and reduction of maintenance cost
Q.3 – Discuss environment and reliability requirements of avionics equipment?
Ans. - Maintenance of environmentally caused avionics equipment failures has been found to be
consuming between 3.4 and 14.1 percent of Air Force maintenance money. It was shown that both
the lower and upper bound estimates for the maintenance cost of environmentally induced avionics
failures are equivalent to the coat of maintaining most other major subsystems in an Air Force
airplane. Specifically, the upper bound estimate is greater than the maintenance cost of any other
major subsystem. Furthermore, it was determined that environmentally induced failures decrease
avionics reliability by a factor of 1.2 to 2.5. Since most avionics equipment items undergo
environmental qualification and reliability demonstration tests prior to service deployment, it must
be concluded that current test methods lack effectiveness in screening out environmentally
sensitive equipment.
The Reliability is an important tool for designing, decision making and estimating future system
success. Design engineers are often required to develop and estimate Reliability before the product
is produced. Inaccurate predictions can lead to over design and excessive spare parts procurement.
This work is based on the study of Reliability Analysis carried out on Electronic Communication
Systems used in the aircraft avionics.
Q.4 – With the help of a neat diagram, explain the principle of radio voice communication?
Also explain the principle of satellite communications.
Ans. - In aviation, communication between the aircraft and the ground (Air Traffic control) have
been by voice communication. After Selecting the appropriate communication channel selector,
pilot transmit a message by pressing the transmit button which connects the microphone to the
appropriate radio. The voice message is used to modulate the carrier frequency and it is composite
signal used to transmitted. The receiver demodulates the incoming signal to recover the original
voice component. High frequency (HF), Very high frequency (VHF) and Ultra High frequency is
the radio communication with different bandwidth region.

Principle of satellite communication:

Satellite communications provide a more reliable method of communications using the
International Maritime Satellite Organization (INMARSAT) satellite constellation which was
originally developed for maritime use. It forms a useful component of aerospace communications.
the aircraft communicates via the satellite constellation and remote ground earth station by means
of C-band uplinks and downlinks to/from the ground stations and L-band links to/from the aircraft.
In this way, communications are routed from the aircraft via the satellite to the ground station and
on to the destination. conversely, communications to the aircrafts are routed in the reverse fashion.
therefore, provided the aircraft is within the area of coverage or footprint of a satellite, then
communication may be established.
The airborne SATCOM terminal transmission frequencies in the range 1626.5-1660.5 MHz and
receives messages on frequencies in the range 1530.0-1559.0 MHz Upon power up, the radio
frequency unit (RFU) scans a stored set of frequencies and locates the transmission of the
appropriate satellites. The aircraft logs onto the ground earth station network so that any ground
stations are able to locate the aircraft. once logged onto the system, communication b/w the aircraft
and any user may begin. the satellite to ground C-band uplink/ downlink is invisible to the aircraft,
as is the remainder of the Earth Support network.

Q.5 – Explain the need of avionics in civil and military aircraft and space system?
Ans. – Avionics are advanced electronics used in aircraft, spacecraft and satellites. These systems
perform various functions including communication, navigation, flight control, display systems,
flight management etc. There is a great need for advanced avionics in civil, military and space
systems.
Need of avionics for civil aircraft:
 For better flight control, performing computations and increased control over flight control
surfaces.
 For navigation, provide information using sensors like Altitude and Head Reference
System (AHRS).
 Provide air data like altitude, atmospheric pressure, temperature, etc.
 Reduce crew workload.
  Increased safety for crew and passengers.
 Reduction in aircraft weight which can be translated into increased number of passengers
or long range.
 All weather operation
 Reduction in aircraft maintenance cost.

Need of avionics for Military aircraft:

 Avionics in fighter aircraft eliminates the need for a second crew member like navigator,
observer etc., which helps in reducing the training costs.
 A single seat fighter is lighter and costs less than an equivalent two seat version.
 Improved aircraft performance, control and better handling.
 Reduction in maintenance costs.
 Secure communication.

Need of avionics for Space systems:

 Fly-by-wire communication system used for space vehicle’s attitude and translation
control.
 Sensors used in the spacecraft for obtaining data.
 Autopilot redundancy system.
 On-board computers used in satellites for processing the data.