Module 4
4.1 Flight instruments
4.2 Working Principle
4.3 Quiz
4.1 Flight instruments
Primary flight instruments provide essential information about an aircraft’s motion, orientation, altitude, speed, and climb/descent. They are fundamental to flight mechanics, pilot decision-making, and aircraft control.
Primary Flight Instruments
Instrument systems
The primary flight instruments are classified based on their operating systems: the Pitot–Static system, which includes the Airspeed Indicator (ASI), Altimeter, and Vertical Speed Indicator (VSI) and works by measuring air pressure, and the Gyroscopic system, which includes the Attitude Indicator (AI), Heading Indicator (HI), and Turn Coordinator (TC) and operates on the principles of gyroscopic rigidity and precession to indicate aircraft orientation and motion.
Airspeed Indicator (ASI)
Function: Measures aircraft speed relative to surrounding air. Principle: Difference between Pitot pressure (total pressure) and static pressure. Flight Mechanics Link: Directly related to dynamic pressure: q=0.5*ρ*V2. Errors: Position error, density error, compressibility (high speed).
Altimeter
Function: Indicates height above mean sea level (MSL). Principle: Static pressure decreases with altitude. Flight Mechanics Link: Determines potential energy of aircraft. Crucial for climb performance and airspace separation. Types of Altitude: Indicated, True, Pressure, Density altitude.
Vertical Speed Indicator (VSI)
Function: Shows rate of climb or descent. Principle: Rate of change of static pressure. Flight Mechanics Link: Related to vertical velocity component. Indicates energy exchange between kinetic and potential energy. Limitation: Lag due to calibrated leak.
Attitude Indicator (Artificial Horizon)
Function: Displays pitch and roll relative to Earth. Principle: Gyroscopic rigidity in space. Flight Mechanics Link: Shows orientation of body axes. Essential for maintaining stable equilibrium. Critical for: Instrument Flight Rules (IFR).
Heading Indicator (Directional Gyro)
Function: Shows aircraft heading. Principle: Gyroscopic stability with magnetic alignment. Flight Mechanics Link: Used in navigation and trajectory control. Helps maintain yaw stability. Note: Must be periodically aligned with magnetic compass.
Turn Coordinator
Function: Indicates rate of turn and coordination. Principle: Gyroscope + inclinometer (slip/skid ball). Flight Mechanics Link: Relates to angular velocity in yaw. Shows balance of centripetal force vs gravity in turns
Location of Primary Flight Instruments in the Cockpit
Primary flight instruments are arranged in a standard "T-configuration" to ensure quick scanning, reduced pilot workload, and safe flight operations.
| Instrument | Cockpit Position | Relative Location | Reason / Flight Mechanics Logic |
|---|---|---|---|
| Attitude Indicator (AI) | Center of panel | Top-center | Primary reference for pitch & roll; core of instrument scan |
| Airspeed Indicator (ASI) | Left of AI | Top-left | Critical for takeoff, climb, approach and stall prevention |
| Altimeter | Right of AI | Top-right | Indicates altitude and energy state of aircraft |
| Vertical Speed Indicator (VSI) | Left of TC | Bottom-left | Shows rate of climb or descent (trend information) |
| Turn Coordinator (TC) | Below AI | Bottom-center | Indicates rate of turn and slip/skid condition |
| Heading Indicator (HI / DG) | Right of TC | Bottom-right | Directional control and navigation reference |
4.2 Working Principle
- AIRCRAFT
- LIGHTER-THAN-AIR
- Airships
- Free balloons
- Captive balloons
- HEAVIER-THAN-AIR
- MAN-POWER-DRIVEN
- NON-POWER-DRIVEN
- Gliders
- Sailplanes
- Kites
- POWER-DRIVEN
- AEROPLANE
- Land plane
- Seaplane (Float/Flying boat)
- Amphibian
- ROTORCRAFT
- Helicopter
- Gyroplane
- Cyclogyro
- ORNITHOPTER
4.3 Quiz
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