For Video Lecture of this presentation: https://youtu.be/8sMbl6pJpd0 The topics covered in this session are, Primary flight instruments: Altimeter, ASI (Airspeed Indicator ), VSI (vertical speed indicator) , Turn-bank indicator. The session is categorized into two portions namely, pitot-static system based and gyroscopic instrument based. Attention! "Gate Aerospace Engineering aspirants", A virtual guide for gate aerospace engineering is provided in "Age of Aerospace" blog for helping you meticulously prepare for gate examination. Respective notes of individual subjects are provided as 'Embedded Google Docs' which are frequently updated. This comprehensive guide is intended to efficiently serve as an extensive collection of online resources for "GATE Aerospace Engineering" which can be accessed free of cost. Use the following link to access the study material https://ageofaerospace.blogspot.com/p/gate-aerospace.html

1. FLIGHT MECHANICS
PRIMARY FLIGHT INSTRUMENTS:
ALTIMETER, ASI, VSI, TURN-BANK INDICATOR
Presented by
Ganesh Natarajan S
Target Audience: Gate Aerospace, Aeronautical
and Aerospace Engineering Students, etc.

2. CORE TOPICS:
Basics: Atmosphere: Properties, standard atmosphere. Classification of aircraft. Airplane (fixed
wing aircraft) configuration and various parts.
Airplane performance: Pressure altitude; equivalent, calibrated, indicated air speeds; Primary
flight instruments: Altimeter, ASI, VSI, Turn-bank indicator. Drag polar; takeoff and
landing; steady climb & descent; absolute and service ceiling; cruise, cruise climb, endurance or
loiter; load factor, turning flight, V-n diagram; Winds: head, tail & cross winds.
Static stability: Angle of attack, sideslip; roll, pitch & yaw controls; longitudinal stick fixed &
free stability, horizontal tail position and size; directional stability, vertical tail position and size;
dihedral stability. Wing dihedral, sweep & position; hinge moments, stick forces.
SPECIAL TOPICS:
Dynamic stability: Euler angles; Equations of motion; aerodynamic forces and moments,
stability & control derivatives; decoupling of longitudinal and lateral-directional dynamics;
longitudinal modes; lateral-directional modes.
SYLLABUS

3. Outline
Let’s Start
PRIMARY FLIGHT INSTRUMENTS
Previous Lecture Airspeed
PITOT-STATIC SYSTEM AND
INSTRUMENTS
• Altimeter
• ASI - Airspeed Indicator
• VSI - Vertical Speed
Indicator
GYROSCOPIC INSTRUMENTS
• Turn-and-slip Indicators
• Turn coordinators

4. PRIMARY FLIGHT INSTRUMENTS
Flight Instruments:
Flight instruments (cockpit) of an aircraft, provide the pilot with data about the flight
situation, such as altitude, airspeed, vertical speed, heading etc. There are six primary flight
instruments namely,
o Altimeter (Pitot Static)
o ASI - Airspeed Indicator (Pitot Static)
o VSI - Vertical Speed Indicator (Pitot Static)
o Turn Indicator (Gyro)
o Attitude Indicator (Gyro)
o Heading Indicator (Gyro)

5. PITOT-STATIC SYSTEM

6. Pitot-Static Flight Instruments
The pitot-static system is a combined system that utilizes the static air pressure and the
dynamic pressure due to the motion of the aircraft through the air. These combined
pressures are utilized for the operation of the airspeed indicator (ASI), altimeter, and
vertical speed indicator (VSI).
• Static pressure (ambient pressure),
is always present whether an
aircraft is moving or at rest.
• Dynamic pressure is present only
when an aircraft is in motion.
• ASI is the only instrument that
utilizes the pitot tube.
• Altimeter and VSI utilize only the
static pressure that is derived from
the static port.

7. ALTIMETER
The pressure altimeter is an aneroid barometer that
measures the pressure of the atmosphere at the level where
the altimeter is located and presents an altitude indication
in feet.
• A stack of sealed aneroid wafers evacuated to an internal
pressure of 29.92 inches of mercury ("Hg).
• These wafers are free to expand and contract with
changes to the static pressure.
Wafer compression = decrease in altitude
Wafer expansion = increase in altitude
The expansion and contraction of the wafers moves the
mechanical linkage which drives the needles on the face of
the altimeter.

8. ALTIMETER
• The altimeter is an instrument that measures the height of
an aircraft above a given pressure level.
• The altimeter uses static pressure as its source of
operation.
• Air is denser at sea level than aloft - as altitude
increases, atmospheric pressure decreases.
• This difference in pressure at various levels causes the
altimeter to indicate changes in altitude.
• Adjustments for nonstandard pressures are
accomplished by setting the corrected pressure into a
barometric scale located on the face of the altimeter
(Kollsman window).
• Cold air is denser than warm air.

9. Airspeed Indicator (ASI)
• It utilizes both the pitot, as well as the static system.
• ASI introduces the static pressure into the airspeed case
while the pitot pressure (dynamic) is introduced into the
diaphragm.
• The dynamic pressure expands or contracts one side of the
diaphragm, which is attached to an indicating system.
• The system drives the mechanical linkage and the airspeed
needle.
The ASI is a differential pressure gauge that measures and indicates the difference between
pitot (dynamic pressure) and static pressure.

10. Vertical Speed Indicator (VSI)
• VSI operates solely from static pressure. It is a differential
pressure instrument.
• Inside of the diaphragm is connected directly to the static
line of the pitot-static system.
• The area outside the diaphragm is also connected to the
static line but through a restricted orifice (calibrated leak).
• The diaphragm receives unrestricted air, the case
receives the static pressure via the metered leak.
• The differential pressure that is indicated on the instrument
needle as a climb or descent.
 Trend information
 Rate information
The rate of climb or descent is indicated in feet per minute (fpm). A VSI indicates whether
the aircraft is climbing, descending, or in level flight.

11. Turn Indicators
There are two types of turn indicators
• Turn-and-slip Indicators : rate of turn in degrees per second
• Turn coordinators: indicates roll rate, and rate of turn.

12. Turn-and-Slip Indicator
• The gyro in the turn-and-slip indicator rotates in the vertical plane corresponding to the
aircraft’s longitudinal axis.
• Because of precession, a yawing force causes the gyro to tilt left or right, as viewed from
the pilot seat.
• The turn-and-slip indicator uses a pointer, called the turn needle, to show the direction and
rate of turn.

13. Primary Flight Displays (PFD)

14. Multi-function display (MFD)

15. PHYSICAL SIGNIFICANCE
 To reduce the possibility of a mid-air collision.
 Unit Conversion: 1 Foot (feet) = 0.3048 metre.
 Flight instruments, inform us where we are.
 They are termed as “primary” because of their
vital function

16. Book Reference
Pilot's handbook of aeronautical knowledge 2016 - Chapter 8: Flight
Instruments (8-1, 8-17), Pg.No: (205-221/524)5
PRIMARY FLIGHT INSTRUMENTS

17. Summary
Pitot-static
System and
Instruments
Gyroscopic
Instruments
Copyright Notice: Images used in this presentation are
sourced from pixabay.com under “Pixabay License” which
are “Free for commercial use and No attribution
required” category (or) from Pilot's handbook of
aeronautical knowledge 2016. This handbook is available
for download, in PDF format, from www.faa.gov.