Aircraft Instruments Quiz

Aircraft Instruments

• Aircraft instruments aid pilots in operating the aircraft more precisely, which leads to enhanced safety and optimal performance.
• Aircraft instruments rely on air pressure differences, gyroscopes, or magnetic fields to operate.

Pressure Instruments (Pitot-Static System)

• Pitot-static instruments utilize air pressure differences to measure speed and altitude.
• The Pitot tube measures impact/ram air pressure, which is affected by the aircraft's speed.
• The static port captures static pressure, providing a reference point for the Pitot-static system.

Airspeed Indicator (ASI)

• The ASI measures the aircraft's speed relative to the air.
• It compares ram air pressure (Pitot tube) with static pressure (static port) to derive airspeed.
• Different colored arcs on the ASI indicate speed ranges:
  • Green: Normal operating range
  • White: Flap-operating range
  • Yellow: Caution range (only in smooth air)
  • Red: Never-exceed speed

Altimeter

• The altimeter measures the aircraft's vertical elevation above a reference point.
• It senses pressure changes and displays altitude in feet.
• It has three pointers to indicate altitude: hundreds, thousands, and tens of thousands of feet.
• The altimeter contains aneroid wafers, which expand and contract with atmospheric pressure.

Vertical Speed Indicator (VSI)

• The VSI indicates the rate at which the aircraft is climbing or descending, measured in feet per minute (fpm).
• The VSI can be inaccurate in turbulent conditions due to a lag of 6-9 seconds.

Gyroscopic Instruments

• Gyroscopic instruments rely on the properties of a gyroscope, a rapidly spinning wheel.
• Gyroscopes exhibit rigidity in space, meaning they remain in a fixed plane of rotation.
• Gyroscopes exhibit precession, a tilting or turning motion in response to pressure.
• A vacuum system powers gyroscopic instruments, supplying vacuum to maintain the rotation of the gyroscopes.

Attitude Indicator (AI)

• The AI displays the aircraft's orientation relative to the earth's horizon.
• It is often referred to as the "master instrument".

Turn Coordinator (TC)

• The TC displays the rate and quality of the aircraft's turn.
• It is a combination of a miniature aircraft indicator and an inclinometer (ball).
• The TC helps pilots establish and maintain constant rate turns.

Heading Indicator (HI)

• The HI displays the aircraft's heading on a 360 degrees azimuth scale.
• It is set by the pilot and provides primary heading information.
• It does not automatically seek true north.
• The HI must be aligned with a magnetic compass every 15 minutes to correct for precession.

Magnetic Instruments

• Magnetic instruments are used primarily for navigation and rely on the Earth's magnetic field.

Magnetic Compass

• The magnetic compass is the only instrument that seeks true north.
• It is used to set the Heading Indicator and verify its accuracy during flight.
• The compass needle aligns with the Earth's magnetic fields.

Magnetic Compass Errors

• Variation: The angular difference between true north and magnetic north.
• Deviation: Differences between indicated magnetic heading and actual heading due to magnetic fields within the aircraft.
• Magnetic Dip: The tendency of the compass needle to point downwards, influenced by the Earth's magnetic field.
  • Accelerating in the northern hemisphere causes the compass to indicate a turn towards north, while decelerating causes a turn towards south.
• Turning Errors: During turns, the compass may lag or lead the actual heading.
  • In the northern hemisphere, the compass indicates a turn to the west when a right turn is entered from a northerly heading.
• Compass Card Oscillation: Erratic movement of the compass card, caused by turbulence or control input.

Engine Instruments

• Engine instruments are used to monitor various engine parameters.
  • Tachometer: Measures engine RPM (revolutions per minute).
  • Oil Temperature Gauge: Measures the temperature of the engine oil.
  • Oil Pressure Gauge: Measures the pressure of the engine oil.
  • Fuel Quantity Gauge: Shows the remaining fuel quantity.
  • Fuel Flow Indicator: Indicates the rate at which fuel is consumed.
  • Exhaust Gas Temperature Gauge: Measures the temperature of exhaust gases.
  • Manifold Pressure Gauge: Measures the pressure in the intake manifold.
  • Cylinder Head Temperature Gauge: Indicates the temperature of the cylinder heads.