3. Text Books:
• 1. Aircraft Instruments and Integrated Systems- EHJ Pallet,
Longman Scientific & Technical, 1992.
Reference Books:
• 1. Aircraft Instrumentation and Systems -S. Nagabhushana & L.K.
Sudha, IK International
• 2. Aircraft Systems: Mechanical, electrical, and avionics subsystems
integration - Ian Moir and Alla Seabridge, Third Edition, John Wiley &
Sons, Ltd., 2008.
3
5. INTRODUCTION
Aircraft Instrumentation-
• A coordinated group of instruments that provide the flight
crew with information about the aircraft and its
subsystems.
• What is Crew?
• A group of 6 to 8 people working in an aircraft
• These instruments provide :
-Flight Situation of that aircraft
-Direction
-Attitude
-Altitude
-Airspeed 5
7. Flight dynamics
Flight steering
The word turbulence can be
used to refer to atmospheric
instability, such as sudden,
unpredictable air movements
resulting from a storm.
7
8. What is the function of the crew?
• To control and monitor instruments during the
flight of an aircraft- thus called controller.
• If aircraft is flying manually, then the adjustments
of systems are initiated manually.
• But if flight of an aircraft and system’s adjustments
are automatic in operation then controller’s
function is monitoring.
8
10. But under failure of systems? ??
controller’s should be able to operate manually.
• Instruments are the means of communication. So the
display system is utmost important.
• Some of the most important requirements of the
display system are:
1. They must be easy to interpret.
2. Reliability should be very high.
3. Pilot effort should be minimum to read and observe data
content.
4. Accuracy of indication should be high.
5. Adequate sensitivity is required to sense small deviations.
6. Repeatability should be high to reduce repeated calibration
efforts. 10
11. The most common forms of data display are:
a) Quantitative display: Variable quantity which is
measured is presented in terms of a numerical value
by moving the pointer or index over a graduated
scale.
• Example- airspeed
b) Qualitative display: Data (changes in parameters
measured) is presented in symbolic or pictorial
format.
Example- flight situation
11
13. The factors that govern the choice of scale length for
a particular range are:
Size of the instrument
Accuracy with which it need to be read
Conditions under which it is to be observed
13
14. Quantitative displays:
There are three principal methods by which data may
be displayed:
i) Circular Scale – clock type of scale
ii) Straight Scale
iii) Digital, or Counter
14
15. i) Circular scale:
Classical method of displaying data in quantitative
form.
A simple indicator showing the change of value of the
parameter to be measured over a range of 0 to 30.
15
16. • In circular displays, again there are two types:
-Linear displays
-Non linear displays:
Square-law : Airspeed
Logarithmic: Rate of altitude change
Square law
16
17. High Range long-scale displays
a) Concentric Scales
b) Fixed and Rotating Scales
c) Common Scale and triple pointers
• Example : Engine speed indicator
17
18. b) Fixed and Rotating Scales
• Used in pneumatic airspeed indicator
• single pointer rotates against a circular scale and
drives a second scale plate instead of a pointer.
• This rotating plate records hundreds of knots as the
pointer rotates through complete revolutions.
19. c) Common scale and triple pointers
• Used in altimeters
• Large pointer indicates hundreds
• Intermediate pointer indicates thousands
• Small pointer indicates tens of thousands of feet
19
20. ii) Straight scale:
• The advantages of using straight scale; saving of
panel space and improved observational accuracy.
• EGT- Exhaust Gas Temperature
20
21. • Each display unit contains a servo-driven white
tape in place of a pointer, which moves in a vertical
plane and registers against a scale in similar manner
to the mercury column of a thermometer.
• There is one display unit for each parameter, the
scales being common to each engine in the
particular type of aircraft.
21
22. • iii) Digital display:
• A digital, or counter, type of display is one that is
generally to be found operating in conjunction with
the circular type of display;
• The presentation of altitude data by means of a
scale and counter is another method of solving the
long-scale problem.
22
23. Dual-indicator display
• These displays are designed for conserving panel
space, particularly where the measurement of
various quantities related to engines is concerned.
23
25. Operational range Markings (Coloured Displays)
• These markings take the form of coloured arcs,
radial lines and sectors applied to the scales of
instruments;
• Their purpose is to highlight specific limits of
operation of the systems with which the
instruments are associated.
25
26. • The definitions of these marks are as follows:
RED radial line: Maximum and Minimum limits
YELLOW arc: Take off and precautionary ranges
GREEN arc: Normal operating range
RED arc: Range in which operation is prohibited
26
27. Qualitative displays:
• These are special type of displays in which
information is presented in a symbolic or
pictorial form to show the condition of a
system.
• It shows whether the value of an output is
increasing or decreasing, or it shows the
movement of flight control surfaces.
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30. Basics of Director displays:
• These displays are associated with the monitoring
of flight attitude and navigational data, and
present it to the flight crew such that, they will be
able to control movements and correct any
departure from a desired flight path. The different
director displays are:
• Gyro Horizon (GH)
• Attitude Director Indicator (ADI)-New
• Electronic Attitude Director Indicator (EADI)-Latest
30
33. • 1.3.1 Attitude Director Indicator (ADI)
• ADI is a primary Flight display which displays all
information critical to flight.
• It indicates pitch (nose up/down) and roll (wings
not level) of the aircraft .
• The commands has to be satisfied by pilot.
33
40. Horizontal Situation Indicator (HSI)
• The HSI is primarily a Navigation display (ND).
• It is an aircraft instrument located in main
instrument panel just below ADI (Attitude Director
Indicator) replacing conventional Gyro Horizon.
• HSI provides a basic horizontal view of the aircraft’s
navigation around the earth.
40
41. Electronic displays:
41
Display
Technology
Operating Mode Typical applications
Light-emitting
Diodes
Active
Digital counter displays of engine
performance
Liquid Crystal Passive
Monitoring indicators; radio
frequency selector indicators;
distance measuring indicators;
control display units of inertial
navigation systems.
Electron CRT
beam
Active
Weather RADAR indicators;
display of navigational data;
engine performance data; system
status; check lists.
42. Light Emitting Diodes (LEDs):
• An LED is a solid state device--forward biased p-n
junction transistor formed from a chip of gallium
arsenide phosphide (GaAsP).
• When current flows through the chip it emits light
which is in direct proportion to the current flow.
42
43. • To obtain different colours, varying proportions of
GaP and GaAs comprising the chip has to be used,
and also by a technique of doping with other
elements, e.g., nitrogen, oxygen etc.
• In a typical seven-segment display format, one LED
per segment is employed.
43
44. Liquid Crystal display:
• LCDs make use of light modulating properties of liquid crystals.
• It consists of two glass plates coated on their inner surfaces with a
thin film of transparent conducting material such as indium oxide.
• The space between the plates is filled with a liquid crystal
compound, and the complete assembly is hermetically sealed with
a special thermoplastic material to prevent contamination.
• When a low-voltage, low current signal is applied to the segments,
the polarization of the compound is changed together with a
change in its optical appearance from transparent to reflective.
• The magnitude of the optical change is basically a measure of the
light reflected from, or transmitted through, the segment area to
the light reflected from the background area.
44
45. 45
Florescent or
LED
backlighting is
required.
The light goes through layers of glass,
polarizers, thin film transistors (TFT),
liquid crystals, and colour filters.
The Thin Film
Transistors
adjust the
amount of light
that passes
through the
colour filters by
controlling the
liquid crystals
The colours and
light combine
to produce the
images you see
on your display.
46. Head-up displays:
• When pilot is maintaining a ‘head-up’ position,
HUDs are used to present flight data in line of sight.
• This display technique is used in military aviation.
HUD systems are used in civil aviation for use in
public transport category aircraft during the take off
and landing phase of flight.
• The principle adopted in a HUD system is to display
the required data on the monitor of a CRT.
46
47. • The display is a combined alphanumeric and
symbolic one, since it is focused at infinity it
permits simultaneous scanning of outside world
and the display without refocusing the eyes.
47
48. Instrument grouping- Flight Instruments
1. AirSpeed Indicator (ASI)
2. Altitude Indicator (ALTI)-Altimeter
3. Attitude Indicator—can be one of the following
Gyro Horizon (GH)
Attitude Director Indicator (ADI)-New
Electronic Attitude Director Indicator (EADI)-Latest
4. Direction Indicator (DI)—can be one of the following
Direct Reading Compass (DRC)
Horizontal Situation Indicator (HSI)---New
Electronic Horizontal Situation Indicator (EHSI)—Latest
5. Vertical Speed Indicator (VSI)
6. Turn and Bank Indicator (TBI)
It is most important for these instruments to be properly grouped to maintain
co-ordination and to assist a pilot in observing them with the minimum of
effort.
48
55. Power Plant Instruments
• The specific grouping of instruments required for
the monitoring of power plant operation is
governed primarily by the type of power plant, the
size of the aircraft and space available for location
of instruments.
• Aircraft power-plant instruments include
tachometers, engine thermometers, pressure
gauges, fuel-quantity gauges, fuel flow meters and
indicators, and manifold pressure gauges.
55
58. Flight deck of modern aircraft (glass cockpit).
• In modern aircraft cockpit is called as ‘glass cockpit’
which has electronic instrument displays similar to
PC glass monitor displays (hence the name glass
cockpit).
• They utilize few computer controlled displays that
can be configured and adjusted to display flight
information as required by pilots.
• There are a large number of computers, sensors
and actuators working behind these computer glass
monitors.
• Such avionic systems increase flight safety, improve
efficiency of the aircraft and greatly assist flight
crew by reducing their workload. 58
