Avionics & Instruments


  • Aircraft became a practical means of transportation when accurate flight instruments freed the pilot from the necessity of maintaining visual contact with the ground
  • Flight instruments are crucial to conducting safe flight operations and it is important that the pilot have a basic understanding of their operation
  • Various types of air navigation aids are in use today, each serving a special purpose
    • These aids have varied owners and operators, namely: the Federal Aviation Administration (FAA), the military services, private organizations, individual states and foreign governments
    • The FAA has the statutory authority to establish, operate, maintain air navigation facilities and to prescribe standards for the operation of any of these aids which are used for instrument flight in federally controlled airspace as tabulated in the Airport/Facility Directory (A/FD)

User Reports Requested on NAVAID or Global Navigation Satellite System (GNSS) Performance or Interference:

  • Users of the National Airspace System (NAS) can render valuable assistance in the early correction of NAVAID malfunctions or GNSS problems and are encouraged to report their observations of undesirable performance
    • Although NAVAIDs are monitored by electronic detectors, adverse effects of electronic interference, new obstructions or changes in terrain near the NAVAID can exist without detection by the ground monitors
    • Some of the characteristics of malfunction or deteriorating performance which should be reported are: erratic course or bearing indications; intermittent, or full, flag alarm; garbled, missing or obviously improper coded identification; poor quality communications reception; or, in the case of frequency interference, an audible hum or tone accompanying radio communications or NAVAID identification
    • GNSS problems are often characterized by navigation degradation or service loss indications
  • Reporters should identify the NAVAID (for example, VOR) malfunction or GNSS problem, location of the aircraft (i.e., latitude, longitude or bearing/distance from a NAVAID), magnetic heading, altitude, date and time of the observation, type of aircraft (make/model/call sign), and description of the condition observed, and the type of receivers in use (i.e., make/model/software revision)
  • GNSS problems are often characterized by navigation degradation or service loss indications
  • Reports can be made in any of the following ways:
    1. Immediately, by radio communication to the controlling Air Route Traffic Control Center (ARTCC), Control Tower, or FSS
    2. By telephone to the nearest FAA facility
    3. For GNSS problems, by internet via the GPS Anomaly Reporting Form at
  • In aircraft that have more than one receiver, there are many combinations of possible interference between units
    • This can cause either erroneous navigation indications or, complete or partial blanking out of the communications
    • Pilots should be familiar enough with the radio installation of the particular airplanes they fly to recognize this type of interference

Airspeed Indicator

Basic Six Pack: