Small Aircraft
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human-Machine Interface; Confusion; Situational Awareness
Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Flight Crew Became Reoriented; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action
Human Factors
We were cleared for the visual approach to [Runway] 28R from the arrival. I set the altitude to 6;000 for the FAF of ZIXIP. My original plan was to fly towards the FAF at 6;000 [feet] then turn base leg then final just inside of it to start my descent after being fully configured. I decided to turn earlier and mistakenly followed what I thought to be my glide slope; therefore; I believed myself to be too high and needing to descend for a stabilized approach. Turning base to final; we got an audible alert of 'obstacle' to which I was searching outside but did not see. Then at the Captain's prompt suggestion I tried to level off but was not aggressive enough. The slow descent resulted in a 'pull up' alert and I was able to maintain altitude but the Captain noted the RA of being around 650 AGL. I was able to continue my turn base to final stabilized and had no other incidents with the event. Lack of situational awareness on my part and last-minute decision to keep a tighter traffic pattern which would require compressed time to configure the aircraft. Mainly; my mistake in believing/following a false glide slope which lead to my confusion. Following the ILS profiles even in VMC conditions for terrain/obstacle clearance. Keeping my situational awareness outside of the cockpit more & remaining vigilant especially in VMC conditions.
Air carrier flight crew reported Terrain Alert on approach to BOI airport.