How should IFR departures from an airport without a control tower be conducted?

• A. File a flight plan 60 minutes before departure by phone; controller issues a clearance that lasts indefinitely.
• B. File a flight plan 30 minutes before departure by phone; controller issues a clearance that lasts indefinitely.
• C. File a flight plan 30 minutes before over the phone; controller will give a clearance that expires if not flown within a certain time
• D. No filing is needed; depart when ready

Answer: (C)

Departing IFR from a field without a control tower requires coordination with ATC before takeoff. You file an IFR flight plan and obtain an ATC clearance so the controller can sequence you with other traffic and provide a departure authorization since there’s no tower to issue it locally.

The standard approach is to file the flight plan about 30 minutes before departure, typically by telephone through Flight Service, so ATC can prepare and issue a clearance. That clearance will come with a time constraint—an expected time of departure or an expiration time. If you don’t depart within that designated window, the clearance can expire and you’d need to reestablish clearance before attempting to depart.

Why the other options don’t fit: there is a requirement to file and obtain a clearance for an IFR departure from a non-towered field, not none at all. And the clearance is not issued to last indefinitely; it carries a time limit to maintain orderly traffic flow.