I’ve been asked before what we do with the second radio on airliners, so I’m here to tell you (this assumes an aircraft with two required radios and a backup). Are you ready? It depends….
If the airplane is equipped with ACARS (Aircraft Crew Alerting and Reporting System, sort of an in-flight email/fax system), most of the time you will monitor 121.5. If the airplane is not ACARS equipped, or if the ACARS is out of service, the procedures will vary a bit from company to company, but most of the time, you will monitor a designated company radio frequency.
Since my airline flies for Delta, we monitor the Atlanta Radio network. That way Delta can spy on us, plus it saves having to build our own network nationwide, which would make it harder for Delta to spy on us. We have available to us a map that shows what frequency we are supposed to use in a given area. There are approximately eight or nine airborne sections of the United States, plus a few each in Canada, Mexico, the Bahamas, et cetera. Because the FARs require that an airline be capable of contacting any airplane at any time, crews must monitor a designated company frequency or have functional alternative, such as ACARS.
There are also a number of locations where dial-up ground frequencies are available.
Our network is guaranteed to work above a certain altitude, again, per the FARs.
As for when the number two radio is used, well, this is the “it depends” area. We can use the company frequency for a number of things: calling for weather updates, advising the company of a hold or delay or a diversion, discussing maintenance issues with the dispatcher or mechanic, passenger service issues, or any number of emergencies or critical events. It can be a little disconcerting to hear a full-blown emergency in progress, especially if you happen to be on the same ATC frequency as the crew that is in distress. But it’s also good to see how others handle certain situations to compare to your own methodology.
Company radio is only supposed to be used for company, flight-specific information, but it isn’t unusual for someone to request football scores or election results. Occasionally, a pair of pilots will recognize each others’ voice on the ATC frequency, and they will switch an air-to-air frequency on the number two radio to chat for a couple of minutes. Not exactly what’s supposed to be done, but it is never for very long, and for the most part it’s no-harm, no-foul.
Closer to the airport, each station has its own frequency, similar to an FBO. Crews will call “in range” anywhere from 10 to 20 minutes out, workload permitting. This is an opportunity to verify the gate and relay any specific needs, which might be mundane (bags of ice) to the more important customer needs (wheelchairs). It’s also a chance to give a station a heads up on any potential delays or issues for the outbound flight.
In short, the number two radio is often used exactly as you use it today in general aviation. With two pilots–especially when something is going wrong–it can be your most valuable asset. In fact, the FARs require at least two functioning primary radios, so if one of them fails, you aren’t going anywhere. It’s that important.–Chip Wright