Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; General Declared Emergency
Aircraft
On climbout passing about FL 180 we received an aural warning and a boxed 'Cargo Fire Lower'. It lasted about two cycles and stopped. We did not see a flashing discharge switch when we looked up as the warning was gone.  This repeated about three additional times with the same result. By the time we would look up the discharge switch was no longer flashing.  We declared an emergency and [began a return to the departure airport] for a visual approach. No smoke or other indications of a fire noted. The aural warnings ceased once we began our [return]. Fire crews saw nothing obvious on the aircraft after landing. Fire trucks escorted us back to the gate and inspected the bellies and found no signs of a fire. We released the aircraft back to Maintenance.
A DC-10 CARGO FIRE LOWER alerted three times with the TRI tone but no flashing discharge switch so an emergency was declared and the flight returned to the departure airport but no sign of fire was seen.