Primary Flight Instruments | Flight Mechanics | GATE Aerospace
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The document provides a detailed overview of primary flight instruments including altimeter, airspeed indicator (ASI), vertical speed indicator (VSI), and turn indicators, along with their operational principles and functionalities. It explains the pitot-static system, how each instrument measures and indicates flight conditions such as altitude and speed, and underlying concepts of drag, stability, and dynamics relevant to flight mechanics. Targeted towards aerospace engineering students, it serves as an educational resource to understand aircraft instrumentation and performance essentials.
Primary Flight Instruments | Flight Mechanics | GATE Aerospace
- 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)
- 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)
- 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.