Date: 202106
Local time of day: 0601-1200
Location: MDST.Airport, FO
Flight conditions: VMC
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Final Approach
ATC / advisory: Tower MDST
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Communication Breakdown
Second reporter function: Pilot Not Flying; Captain
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action
Contributing factors: Airspace Structure; Chart Or Publication; Manuals; Procedure
Primary problem: Procedure

Narrative: The Captain and I were operating a flight to MDST from ZZZ. We thoroughly briefed and read the pertinent information for the arrival into MDST since we had never been to that airport. We briefed and expected to get the SEKAR 2P [Arrival] for Runway 11 at MDST; which we did. Upon descent; we received clearance to 6000 ft to SEKAR. Upon passing SEKAR; we were cleared direct to OMRUP and cleared approach to Runway 11. OMRUP is not on the arrival; but the approach portion going into MDST. In the FMC; we brought OMRUP up and inserted it into the line below SEKAR and verified the route. Aircraft was still in VNAV PATH and because the altitude along the route was a descent from 6000 to 4000; we selected 4000 and continued the descent in VNAV. This is where we realized something wasn't right. There is high terrain surrounding the airport and it is briefed on the briefing pages in the EFB (Electronic Flight Bag). We reached approximately 5000 and decided immediately to climb back to 6000 because the MSA along the arrival track is 5500 from RETAK to OMRUP. We climbed and maintained 6000 until we passed the high terrain. Once we cleared the high terrain; we proceeded to fly the approach without further incident. We never got a terrain alert as we didn't allow ourselves to descend further into high terrain. The Captain and I used excellent CRM to avert a potentially serious situation. The Captain's situational awareness and experience arriving at an unfamiliar airport were a tremendous asset to recognizing and correcting a potential hazard.


Second narrative: The First Officer and I were operating a flight to MDST from ZZZ. We thoroughly briefed and read the pertinent information for the arrival into MDST since we had never been to that airport. We briefed and expected to get the SEKAR 2P [Arrival for Runway 11 at MDST; which we did. Upon descent; we received clearance to 6000 ft to SEKAR. Upon passing SEKAR; we were cleared direct to OMRUP and cleared for the approach to Runway 11. OMRUP is not on the arrival; but the approach portion going into MDST. In the FMC; we brought OMRUP up and inserted it into the line below SEKAR and verified the route. Aircraft was still in VNAV PATH and because the altitude along the route was a descent from 6000 to 4000; we selected 4000 and continued the descent in VNAV. This is where we realized something wasn't right. There is high terrain surrounding the airport and it is briefed on the briefing pages in the EFB. We reached approximately 5000 and decided immediately to climb back to 6000 because the MSA along the arrival track is 5500 from RETAK to OMRUP. We climbed and maintained 6000 until we passed the high terrain. Once we cleared the high terrain; we proceeded to fly the approach without further incident. We never got a terrain alert as we didn't allow ourselves to descend further into high terrain. The First Officer and I used excellent CRM to avert a potentially serious situation. His situational awareness and knowledge was a tremendous asset to recognize a potential hazard.


Synopsis: Air carrier flight crew reported anomaly with approach altitude allowing descent below MSA.