Light Transport; Low Wing; 2 Turbojet Eng
Confusion; Situational Awareness; Workload
Inflight Event / Encounter CFTT / CFIT
Flight Crew Became Reoriented
Human Factors; Procedure
While on arrival to CEU we anticipated the RNAV approach to Runway 7. Weather was clear so instead we briefed a visual approach to Runway 7 with a plan to overfly the departure end and enter the right downwind for runway 7. ATC left us high on the arrival so we were expediting down to get to Traffic Pattern Altitude (TPA). I set 1600 in the altitude alerter since I believed that the TPA was 1600. I believed it to be 1600 because I had mistakenly misread the chart and added 1500 to the Threshold Crossing Height (TCH) instead of the TDZ Elevation on the approach chart for RNAV 7. I entered the downwind and arrested my descent rate but was still gradually descending in the traffic pattern when I noticed that we seemed quite low. I verified the altimeter setting and stopped my descent. While beginning to initiate a climb we received a 'Terrain Terrain Pull Up' GPWS warning. I immediately disconnected the autopilot and continued the climb manually. It was at this time the GPWS warning stopped and since the weather was clear VFR; I could see that there was no threat of terrain so I continued my visual approach to the runway and did not fly an escape maneuver. When I briefed the visual approach; we should have read and cross verified the APT ELEV number instead of looking at the number on the approach chart and assuming that was the airport elevation. I will be more vigilant in the future to do so.
Light Jet Captain reported a GPWS Terrain warning after descending to a traffic pattern altitude based upon a mistaken airport elevation.