Frequent question: Why is the aircraft emergency called guard?

What does it mean when an air traffic controller says on guard?

RE: ATC Term “On Guard”

Guard is another term for 121.5 (and other prescibed frequencies), the international distress frequency. As many aircraft monitor this frequeny it is sometimes used as a backup to contact an aircraft that has not responded on the ATC frequency.

What does 121.5 mean in aviation?

121.5 MHz is generally reserved for civilian distress or emergency use, with 243MHz used for military operations (although you do hear military aircraft also on 121.5 MHz). If ATC (Air Traffic Control) are unable to reach aircraft on their assigned frequency they will try to call them on guard frequency.

What does radio Guard mean?

A ship, aircraft, or radio station designated to listen for and record transmissions and to handle traffic on a designated frequency for a certain unit or units. Dictionary of Military and Associated Terms.

What is military guard frequency?

121.5 MHz is a guarded frequency, hence the “Guard” comment you constantly hear. 121.5 MHz, and UHF 243.0 MHz for military operations, are monitored by ATC and others, including maritime agencies.

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Why is 121.5 called guard?

It is called guard because everybody is supposed to listen/guard the frequency just in case someone has a problem. Guard definitions: a state of caution, vigilance, or preparedness against adverse circumstances. watch over in order to protect or control.

What is the UHF emergency frequency?

Channel 5 and 35: are the designated emergency channels, and are not to be used except in an emergency. To make an emergency call, switch your radio to Channel 5 with duplex on, if there is no response, try again with duplex off.

Who controls communications when you are in distress?

6.6 Control of Distress Traffic

The control of distress traffic is the responsibility of the aircraft in distress or of the station which relays the distress message.

What is the purpose of guard bands?

In radio, a guard band is an unused part of the radio spectrum between radio bands, for the purpose of preventing interference. It is a narrow frequency range used to separate two wider frequency ranges to ensure that both can transmit simultaneously without interfering with each other.

What frequency does an ELT transmit on?

ELTs of various types were developed as a means of locating downed aircraft. These electronic, battery operated transmitters operate on one of three frequencies. These operating frequencies are 121.5 MHz, 243.0 MHz, and the newer 406 MHz. ELTs operating on 121.5 MHz and 243.0 MHz are analog devices.

Why is a guard band allowed at the higher end of channel width spectrum?

A guard band is a narrow frequency range that separates two ranges of wider frequency. This ensures that simultaneously used communication channels do not experience interference, which would result in decreased quality for both transmissions.

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