Date: 201408
Local time of day: 0601-1200
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Oil Line
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Distraction; Situational Awareness; Troubleshooting
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Critical
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Flight Crew Inflight Shutdown; Flight Crew Landed in Emergency Condition; Flight Crew Diverted; General Declared Emergency; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: We were flying back on an AM out and back at FL360 when we noticed that the engine oil in the #1 engine was decreasing. The engine oil indication decreased to zero in about one minute (approximate). We monitored engine oil pressure and temperature and then noticed the engine oil pressure decreasing. Having no other abnormal indication; I directed the First Officer to run the engine shutdown checklist. Concurrently; I advised ATC of our engine problem; declared an emergency and communicated that we would be diverting. ATC provided vectors and descent. I asked for Runway XX but it was closed due to construction. We advised that we preferred Runway XY. During the initial stages of the emergency; I asked that the jumpseating qualified crewmembers come forward to assist. I asked for their assistance in contacting Dispatch via ACARS to advise company of our status and intention to divert.  The First Officer ran the emergency checklists with the jumpseater assisting. I solicited input from all crewmembers. Checklists and briefings were completed and we were then provided vectors to the runway.  I elected to have the aircraft autoland.   We stopped aircraft on the runway so the crash and fire rescue could look at the airplane which they reported that the aircraft had no 'hot spots.'  With the report from the crash and fire rescue; we taxied to our ramp with the crash and fire rescue crew behind us as an additional safety measure. We taxied into our parking spot; shutdown engines; and then debriefed what had just happened.   After shutdown; I made an AML entry for the engine oil leak. I also contacted the Duty Officer after the event before we went to the layover hotel. The First Officer did an excellent job; period. The jumpseaters were also very helpful and did a great job. I'm not certain what caused the oil line to shear. Mechanic said that this was unusual.


Second narrative: Upon further investigation the Mechanic informed us that the oil line that leads to the gear box had sheared completely off.


Synopsis: The number one engine oil quantity decreased to zero followed by an oil pressure drop; so the engine was shutdown; an emergency declared and the flight diverted to a nearby airport for an uneventful emergency landing. A gear box oil line had sheared.