Does anyone know what an "alert 2" refers to? I think it has something to do with the airport because CFD dispatched units there after a distressed plane was reported to be landing, but what specifically does it mean, and are there other alerts?
Alert 2 is a response level used at the airport by ARFF (Airport Rescue and Fire Fighting).
Alert 1 - Ramp standby (not used too often)
Alert 2 - ARFF units set up at pre-position locations
Alert 3 - Actual or impending crash
Alert 2 is the most common and is called by the tower over the crash loop (dedicated PA line to the airport communications center and fire station) when an inbound aircraft has a problem. ARFF units will respond and take up pre-established positions along adjacent taxiways which are determined by a variety of factors, including whether the incoming aircraft is heavy and how much runway it is expected to need.
Columbus FD is a mutual aid department to the Airport Fire Department, which has primary responder duties and the appropriate training. Often, an alert will be resolved and cleared before CFD even gets the run dispatched, so CMH ARFF (or LCK ARFF) are good talkgroups to monitor if you're interested in hearing the activity.
One other thing... you'll virtually
never hear an aircraft actually declare an emergency. The only thing you're likely to hear is "we seem to have a problem here" or something equally low-key, so you'll probably miss it if you're monitoring aviation channels.