Regional Jet 900 (CRJ900)
Flight Crew Air Transport Pilot (ATP)
ATC Issue All Types; Aircraft Equipment Problem Critical
Flight Crew Diverted; Flight Crew Landed in Emergency Condition
Aircraft
We experienced a DC EMER BUS caution message. We ran the QRH. The first line in the QRH for this event was 'land at nearest suitable airport.' We (the FO and myself) discussed the situation and made a plan. We [advised ATC] diverted to [a nearby airport]. This gave us enough time to prepare the plane for landing. We asked ATC to roll the fire trucks as we no longer had any system fire protection and lost our DC Emergency Bus (electrical). I [briefed] the flight attendants. I made an announcement to the passengers that we were diverting due to mechanical issues. I ACARS texted Dispatch to let them know our plan. We landed and taxied to the gate without further incident. We deplaned the passengers and shutdown the aircraft. I have a concern in this event. The Tower Controller cleared an aircraft to takeoff in front of me when we were at 500 ft. The aircraft was slow to depart. I queried the Tower Controller again if we had been cleared to land. Had that aircraft had any difficulties on the runway; we would have had to go around. No aircraft in an emergency that needs to 'land at nearest suitable airport' would like to accomplish a go around; for any reason. I understand the ATC description of the 'Safe; efficient flow of traffic.' Unfortunately in this event I believe 'efficient' took precedence over 'safe.' During normal traffic flow it would have been good work; but not during an emergency.
CRJ-900 Captain reported diverting to a nearby alternate after experiencing a DC EMER BUS caution message.