Cessna Citation Sovereign (C680)
Flight Crew Air Transport Pilot (ATP)
Training / Qualification; Workload
Aircraft Equipment Problem Critical
Flight Crew Landed in Emergency Condition; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Returned To Departure Airport; General Declared Emergency
Aircraft
Shortly after takeoff; after retracting gear and flaps; we received an amber CAS message 'HYD VOL LOW'.  I immediately directed the SIC/Pilot Monitoring to put the gear down. We told Departure we had to return to the airport; and declared an emergency. The Pilot Monitoring ran the checklist; and we finished the checklist.  We landed uneventfully; but had to use the emergency (pneumatic) braking system since we lost all hydraulic functions including brakes; anti-skid; thrust reversers; and spoilers/spoilerons.  We had enough emergency nose wheel steering to exit the runway and stopped on a taxiway; where two fire trucks met us.  We were then towed to the FBO. There was a large amount of hydraulic fluid dripping from the aircraft; and there appeared to have been a leak from the nose gear compartment.
A CE-680 CAS alerted HYD VOL LOW after retracting the gear and flaps so the gear were lowered immediately; an emergency declared and the flight returned to the departure airport with the loss of all hydraulic fluid.