Date: 202006
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class D ZZZ
ATC / advisory: TRACON ZZZ
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Training / Qualification; Distraction; Situational Awareness; Confusion
Anomaly: Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed As Precaution
Contributing factors: Procedure; Environment - Non Weather Related; Human Factors; Airspace Structure
Primary problem: Human Factors

Narrative: The Captain was making his visual approach to the runway; which ATC assigned as the one coming over mountainous terrain. The Captain asked for flaps and gear early to aid the descent and slow our ground-speed. All but flaps 45 had been input. I noted the radar altimeter was 1;500 or 1;600 feet; at which time I notified the Captain we needed to get flaps 45 in before 1;000 HAT. He made the standard callout shortly thereafter; as I once again inquired whether we were okay to do so. He said we were. As we arrived at short final the glideslope alert sounded; followed by a brief 'pull up' alert. The Captain flared and landed; to my memory; between the 1;000 and 1;500 foot markers. We stopped well short of the end of the runway; taxied clear; and proceeded to the gate.Ultimately; I am uncertain on two fronts: 1) whether I input flaps 45 too late; and; 2) the significance of the 'pull up' call given I remember getting it once in the sim and was told; as I recall; it happens at some airports.This was my first time into this airport. The Captain has been there numerous times and was very familiar. Additionally; this was my first flight leg after almost three months of being off. Despite my studying to refresh myself prior to reengaging flight duties; I noted some rustiness was present. While the approach seemed high; I noted I was deferring quite substantially to the Captain's judgment with the surrounding terrain given his ongoing familiarity of the mountains and issues common to this airport. That combined with my regaining of my flight deck duty pace; my awareness and confidence being back in the airplane were surely suffering. Additionally; the runway had a significantly displaced threshold; adding to what I'm surmising might be some perception issues given the captain landed the aircraft near the thousand foot markers.As I've had time the rest of today to contemplate the events; I've realized one bad habit I've made during my time in this job. When I noted the radar altimeter and thought we were too late for flaps 45 and the Captain remarked we were not late; I never actually noted our barometric altitude. And we were descending overhead mountainous terrain as I recall. So; the RA may very well have been misleading me and ultimately unnecessarily adding to my confusion and lack of confidence. Moving forward; I want to teach myself to have a barometric altitude number in mind prior to arrivals and not hone in on the RA to feed my awareness of the 1;000 HAT flaps in; stabilized threshold. For instance; at a given airport 1;800 feet MSL might be the 1;000 HAT number to be watching for on the barometric altimeter. Yet; if approaching over terrain; the barometric altimeter may be reading 2;500 feet MSL while the radar altimeter could be reading 1;000 feet. That was a big lesson learned for me today. Then; I do also wish I would have suggested to the Captain to take the reverse runway given the light winds. I'm still at a loss as to why ATC assigned a terrain-tight runway when winds favored the runway with greater terrain separation.




Synopsis: Air carrier First Officer reported a CFTT incident citing unfamiliarity with the airport and issues relating to the surrounding terrain.