Flight Instruments

  • Pitot tube measures both static pressure (ambient pressure / barometric pressure) and dynamic pressure
  • Airspeed Indicator (ASI) uses both static and dynamic pressure
  • Vertical Speed Indicator (VSI) and Altimeter use only static pressure
  • 1 inch of pressure is equal to approximately 1,000 feet of altitude. E.g. if altimeter is not adjusted from 29.94 to 29.69, 29.94-29.69=0.25, 0.25 × 1,000 feet = 250 feet. the aircraft would be approximately 250 feet below the proper traffic pattern altitude. When the actual pressure is lower than what is set in the altimeter window, the actual altitude of the aircraft is lower than what is indicated on the altimeter


The six primary instruments (the “six-pack”) are the Attitude Indicator (AI), Heading Indicator (HI), Turn Coordinator, Airspeed Indicator, Altimeter, and the Vertical Speed Indicator (VSI).

  • pilot-static system: air speed indicator, vertical speed indicator (VSI), altimeter
  • The gyroscopic instruments include the Attitude Indicator (AI), Heading Indicator (HI), and Turn Coordinator.
    • use a mechanical gyroscope that is either pneumatically (vacuum) or electrically driven. The gyroscope consists of a spinning disc that rotates freely around specific axes, depending on the instrument.

Pitot-Static Instruments

  • pitot tube clogged: altimeter inoperative.
  • static vents clogged: airspeed, altimeter, vertical speed inoperative.


3 speed: indicated, calibrated, true

  • indicated (IAS): what you read
  • calibrated (CAS): corrects based on the aircraft?
  • true (TAS): corrects calibrated airspeed for variations in air density (affected by altitude and temp); A very simple rule of thumb is to add 2% to the calibrated airspeed for every 1000 ft of altitude.


  • white arc: the flap operating range.
    • lower: V_s0 power-off stalling speed, full flaps, max weight
  • green arc: the normal operating range.
    • lower: V_s1, power-off stalling speed, flaps up, max weight.
  • yellow arc: the caution range; should only be flown in smooth air.
    • lower: V_NO, max structural cruising speed.
    • upper (red line): V_NE, never exceed speed

Other speed:

  • V_A: maneuvering speed. VA changes depending on the weight of the airplane, is not marked
    • No full or abrupt control movements allowed above this airspeed.
  • V_Y: the best rate-of-climb speed (the most altitude in a given period of time)
  • V_X: the best angle-of-climb speed (the most altitude in a given distance)

Stall speed: Turns, turbulence, and extra weight increases stall speed.

Glass Cockpit

  • AHRS: attitude and heading reference system
  • ADC: air data computer, for airspeed, altitude.