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How may unreliable airspeed be recognised?

  • A
    The Pilot will receive some kind of vibration through flight controls.
  • B
    Different airspeed indications are shown between ASIs.
  • C
    Unreliable airspeed indications do not affect helicopters.
  • D
    Uncommanded cyclic and yaw control may be experienced.

Unreliable Airspeed describes a situation where the airspeed indicators on an aircraft are providing inaccurate or unreliable readings.

Unreliable airspeeds can be recognised by:

  • different airspeed indications between ASIs by 5 knots or more
  • unexpected aircraft behaviour and attitudes
  • buffeting
  • aircraft system warnings
  • Comparing with GPS speed indications

Ways to prevent such situations include:

  • Inspect all pitot heads and static ports during the pre-flight inspection.
  • Use pitot/static heat.
  • Understand the relationship between the ADC, the autopilot and flight director. Disconnect the latter two, plus the autothrust.
  • Monitor primary flight path parameters (pitch attitude, thrust setting and IAS) during periods of potential icing.
  • Be aware of normal attitudes and power/thrust settings for the various phases of flight.
  • Keep away from the low- and high-speed ends of the flight envelope.
  • Revert to safe default parameters for pitch attitudes and thrust settings.
  • Remain in VMC, if possible.
  • Advice GPS speed indications.

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