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Instruments

AIRCRAFT INSTRUMENTS AND WHAT THEY DO

cockpit

 

Airspeed Indicator (ASI)

Shows speed of airflow in knots kt (nautical miles per hour), kilometers per hour kph, or (statute) miles per hour mph.

Altimeter

Shows altitude, usually with reference to sea level, but can be adjusted to local pressure to give height above the ground.  Above about 3000′ is usually set to 1013 mb or 29.92″, depending on its units.

Attitude Indicator (AI) or Artificial Horizon (AH) 

Displays angle of pitch (nose-up or -down) and angle of bank of aircraft.

Avionics switch 

Allows all the electrical navigation units to be switched on together.

Clock  

Adjust to GMT (Zulu) or zero at start to show total flight time.

Digital Measuring Equipment (DME)

Measures the distance from a beacon and can display the bearing (VOR/DME).

Direction Indicator (DI) or Heading Indicator (HI)  

Shows direction or heading; may need readjustment from time to time as the internal gyroscope gradually moves its axis of rotation.  Responds quickly as the aircraft turns, unlike the magnetic compass.

Exhaust Temp and Fuel flow gauges

Helps monitor the engine and the fuel burn.

Electric Fuel Pump 

Used to ensure a good flow of fuel for take-off, landing and when changing the fuel tank in use.

Flap selector (electric)     

Used to lower or raise the flaps.  Flaps down increases lift so the aircraft can fly slower, and it helps to lower the nose for better forward view when landing.  Flaps also increase the air resistance and slows the aircraft.

Fuel Gauges  

Gives an idea of how much fuel is left in each tank.  Pilots do a calculation on how much fuel they will need for a flight, and allow 45 minutes of reserve.  NEVER assume the gauge is accurate – ALWAYS check the actual tank levels before a flight.

Fuel tap

Used to change fuel tank in use.  Usually with a tank in each wing, the pilot uses part of each tank at a time to help balance.

Magnetic Compass 

Displays direction compared with magnetic north; better placed away from the electrical instruments and well clear of steel items.  Used to check the DI from time to time.  Needs its error checking at the main compass points if you modify the instrument panel, and from one year to the next.

Magneto Switch  

Turns on ignition to one or both magnetos, and on this aircraft makes the starter motor turn.

Manifold Pressure Gauge and Ammeter   

Helps adjust the mixture when at height, and the ammeter allows a check on the rate of battery charging.

Master Switch

Turns on power and alternator (usually after starting).

Mixture Control  

Adjusts the amount of fuel mixed with air – rich means more fuel, lean means less fuel.

Navigation Instruments

A wide variety of instruments to show radio, satellite, or inertial navigation information.

Oil Temperature and Pressure Gauges 

Gives information about the engine state, and a warning if oil is being lost or the engine is overheating.

Radio Selector

Switch array to select which channel of COM1, COM2, NAV1 or NAV2 is being received.

Radio Stack 

Contains communications and navigational radios;

Suction or Vacuum Gauge 

Shows the amount of Suction or Vacuum present for the vacuum-driven instruments

Switches 

Turn on various lights and other devices.

Tachometer 

Indicates engine speed in revolutions per minute (RPM).

Throttle knob

Push in to increase engine speed, and pull out to decrease.

Transponder

Communicates with ground-based radar by sending down information for identification and height.

Electric Pitch Trim

Adjusts the elevator to lift or lower the nose a little, to help the aircraft fly level without constant yoke inputs.

Turn and Slip Indicator   

Shows the way the aeroplane is turning, and if it is out of balance.

Vertical Speed Indicator (VSI)

Indicates rate of climb or descent, usually in feet per minute.

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