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the taxiway on its way to the runway and again for takeoff clearance, the pilot contacts ground control to
get taxi clearances.
Shortly after takeoff, the pilot contacts departure control: “KLM 662, radar contact, climb and maintain
FL320, turn right heading 120, proceed on course.” From then on, the pilot contacts flight controllers upon
reaching predefined altitudes or when entering a different flight-control center's airspace. Approximately
30 minutes before reaching its destination, the aircraft begins its descent, and the pilot contacts approach
control. Just before landing, you hear the final clearance: “KLM 667 heavy, winds 030 at 12, cleared to
land runway 33.”
1
Passive Monitoring
In 1961, the FCC (Federal Communications Commission) prohibited the operation of FM receivers on
board aircraft since they were determined to interfere with the operation of navigation and
communication systems. The FAA (Federal Aviation Administration) subsequently determined that other
personal electronic devices could be potentially hazardous to aircraft systems if operated aboard aircraft
and prohibited their use.
Figure 1 – Standard receiver vs. passive monitor. Standard heterodyne receivers have one or more oscillators that produce radio
signals used for tuning to a desired frequency. Signals from these oscillators that escape the receiver may interfere with
communication and navigation signals. In contrast, a passive monitor does not contain any oscillators or other radio-frequency
sources that may radiate interfering signals.
