Narrative:

Flying to ttpp in intermediate IMC conditions. Ca acting as PF and first officer as pm. Airport conditions indicated a landing to west on runway 28 with an RNAV approach. There was discussion as to whether they were actually using the west runway as it was rarely used. Ca believed they would be landing runway 10 with a slight tailwind so we calculated the landing distance with tailwinds to verify distance was adequate for conditions. PF briefed approach landing runway 10 with the addendum that we would switch to runway 28 if ATIS stated runway 28.upon contacting piarco approach verified runway 28 as landing runway and rebriefed the approach as they initially cleared us to bosot. We requested position VOR as a fix instead of bosot as to remain on the other side of the terrain. There was some confusion as to where center was clearing us to from our position as there were no feeder fixes to reach bosot from our position. At this point we accepted sebas instead of bosot as a fix and entered sebas as a waypoint to link to bosot. PF rebriefed that we were going to cross over terrain to sebas which was 2500 and we had already briefed 4100 ft as MSA. Approximately 25-30 miles from airport at 5000 ft we were cleared direct bosot and cleared for the approach. PF selected appr mode and we verified final app and V/deviation presentation while descending to 4100 ft to cross terrain and begin approach. Ca had weather display up and first officer had terrain up on screens.somewhere before bosot; ca set 2500 ft as his next step down altitude for bosot. As not to have too steep of a descent angle toward terrain ca used vertical speed to shallow his descent and inadvertently descended below the correct altitude. I was communicating with piarco center and tower controllers and was unaware that he had switched to vertical speed mode. I realized we were too low and stated that we needed to return to MSA of 4100 ft. During this time there was some confusion as to which altitude should have been set; why we lost the protection of 4100 ft as a floor and why we continued descent to 2500 ft pushing us below where we should have been. As ca was starting to correct his descent and climb the terrain warning was activated. Ca immediately performed the escape maneuver climbing away from the terrain. At this point we were in VMC conditions with the runway in sight. Ca disconnected automation and performed a stabilized VMC approach to land.flying around terrain is a normal hazard of our operations. While many rules and procedures have been developed to mitigate dangers situational awareness is paramount. As pm I should have been more proactive in monitoring our position; where we were asking the FMS to take us and communicating and verifying what was actually happening. Confusion as how to set up the FMS was allowed to override the attention to critical altitudes and verifying ATC clearance and altitude restrictions. Adherence to strict monitoring of altitudes and our position should have prevented us from ever descending below a safe altitude. Reintegrating where we were in position to the terrain we were crossing and our next safe altitude should have been our most important and clear concern. Clear communication should have been better on my part to prevent this situation.

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Original NASA ASRS Text

Title: Air carrier flight crew reported that while flying the TTPP RNAV (GPS) Runway 28 Approach they descended below the 4;100 feet MEA enroute to SEBAS which activated the EGPWS at about 3;750 feet. The Captain executed the escape maneuver to VMC conditions then continued the approach.

Narrative: Flying to TTPP in intermediate IMC conditions. CA acting as PF and FO as PM. Airport conditions indicated a landing to west on RWY 28 with an RNAV approach. There was discussion as to whether they were actually using the west RWY as it was rarely used. CA believed they would be landing RWY 10 with a slight tailwind so we calculated the landing distance with tailwinds to verify distance was adequate for conditions. PF briefed approach landing RWY 10 with the addendum that we would switch to RWY 28 if ATIS stated RWY 28.Upon contacting Piarco Approach verified RWY 28 as landing RWY and rebriefed the approach as they initially cleared us to BOSOT. We requested POS VOR as a fix instead of BOSOT as to remain on the other side of the terrain. There was some confusion as to where center was clearing us to from our position as there were no feeder fixes to reach BOSOT from our position. At this point we accepted SEBAS instead of BOSOT as a fix and entered SEBAS as a waypoint to link to BOSOT. PF rebriefed that we were going to cross over terrain to SEBAS which was 2500 and we had already briefed 4100 ft as MSA. Approximately 25-30 miles from airport at 5000 ft we were cleared direct BOSOT and cleared for the approach. PF selected APPR mode and we verified FINAL APP and V/DEV presentation while descending to 4100 ft to cross terrain and begin approach. CA had weather display up and FO had terrain up on screens.Somewhere before BOSOT; CA set 2500 ft as his next step down altitude for BOSOT. As not to have too steep of a descent angle toward terrain CA used Vertical speed to shallow his descent and inadvertently descended below the correct altitude. I was communicating with Piarco center and tower controllers and was unaware that he had switched to vertical speed mode. I realized we were too low and stated that we needed to return to MSA of 4100 ft. During this time there was some confusion as to which altitude should have been set; why we lost the protection of 4100 ft as a floor and why we continued descent to 2500 ft pushing us below where we should have been. As CA was starting to correct his descent and climb the terrain warning was activated. CA immediately performed the escape maneuver climbing away from the terrain. At this point we were in VMC conditions with the runway in sight. CA disconnected automation and performed a stabilized VMC approach to land.Flying around terrain is a normal hazard of our operations. While many rules and procedures have been developed to mitigate dangers situational awareness is paramount. As PM I should have been more proactive in monitoring our position; where we were asking the FMS to take us and communicating and verifying what was actually happening. Confusion as how to set up the FMS was allowed to override the attention to critical altitudes and verifying ATC clearance and altitude restrictions. Adherence to strict monitoring of altitudes and our position should have prevented us from ever descending below a safe altitude. Reintegrating where we were in position to the terrain we were crossing and our next safe altitude should have been our most important and clear concern. Clear communication should have been better on my part to prevent this situation.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.