Date: 201506
Local time of day: 0001-0600
Location: EUG.Airport, OR
Flight conditions: VMC
Light: Night
Aircraft: Medium Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class E ZSE
ATC / advisory: Center ZSE
Reporter organization: Air Carrier
Reporter function: Pilot Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Fatigue; Situational Awareness
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Unstabilized Approach
Detector: Automation Aircraft Terrain Warning
When detected: In-flight
Result: Flight Crew Became Reoriented; Flight Crew Took Evasive Action
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: On an approach to EUG at night with runway and airport environment in sight; we were cleared for a visual approach at 10;000 FT; and runway our discretion; as at the time of this approach; EUG tower was closed and the airport was uncontrolled. Upon initiating the descent from 10;000 FT; I as the pilot flying; realized that the aircraft was too high and a straight-in approach to the runway using a normal descent rate would not be possible. (This was the result of me as pilot flying accidentally setting up the FMS such that it was providing me with less than sufficient descent rate for me to descend from the cruise altitude and reach the 30 mile ring from EUG at 10;000 FT. When I set up the FMS to provide the descent guidance; I did ask the Captain to verify the changes I had made before I pressed the execute button; however he did not voice any concerns).I quickly communicated my concern with the Captain who was the pilot monitoring and suggested a go-around. The Captain at this point suggested a descending left 360 degree turn to lose the altitude. He then advised the ATC that we would like to perform a left 360 degree turn to lose altitude. ATC replied 'Maneuver at your discretion; cleared for the visual runway 34L; cancel IFR in the air or on the ground on this frequency'.While performing the 360 degree turn; when we reached the right base for runway 34L; we received a GPWS caution. Upon receiving the caution; I immediately disconnected the auto pilot; applied max thrust; retracted the spoilers; and pitched up. As a result; the alert went away.  We then configured the aircraft for a normal approach into EUG and landed uneventfully.There were three root causes for this event:1. I incorrectly set up the FMS for it to provide me with the descent guidance to 10;000 FT at the 30 mile ring from the airport and as a result; the instrumentation was providing the descent rate that was not sufficient for us to be at 10;000 FT; 30 miles away from EUG.2. The Captain's instructions to make a left 360 turn to lose altitude. The appropriate procedure would have been to make 'S' turns; or fly to the field and then enter left traffic pattern for runway 34L and lose the altitude in a safer manner.3. It was late at night and both [of us] were a bit tired.1. To always verify and re-verify that the FMS has been setup correctly such that the descent rate guidance to 10;000 at 30 mile from the airport is set up properly and for the pilot monitoring to more carefully check the FMS before accepting said changes.2. To avoid performing a descending 360 degree turn. Instead perform 'S' turns or overfly the field; keeping it in sight and enter the appropriate traffic pattern in case the altitude is to be corrected.3. Request for vectors from ATC to more safely lose altitude; execute a published missed approach and perform another approach.




Synopsis: Regional Jet First Officer reported receiving a GPWS terrain warning; while performing a 360 to lose altitude; on a night visual approach to EUG.