Commercial Fixed Wing
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Situational Awareness
Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Unstabilized Approach
Flight Crew Became Reoriented; Flight Crew Executed Go Around / Missed Approach
Human Factors
We chose to fly the RNAV X 28R into Boise. We briefed the approach in cruise including the 180 speed restriction at CUBAR. We flew the plane through CUBAR at 210 by mistake. Shortly afterward we heard the audible alert 'TOO LOW TERRAIN.' We briefly discussed and concluded the alert was a result of our high speed; and we could see there was no terrain in or near our flight path. Our discussion set us behind the airplane. We promptly slowed and put the gear down to configure to land. The gear came down and we continued to configure to flaps 10. Once we were on final we made the decision to go missed because we were not in a normal position to land (not configured by 1;000 ft).As the flaps retracted through 10 degrees and the gear was raising we received another audible: 'TOO LOW GEAR.' Our missed was successful and our second approach on the RNAV X 28R was flown well within the speed restrictions to a safe landing.The VFR weather in Boise distracted me from monitoring the speed restrictions along the approach. It is a requirement to follow speed restrictions on approaches that one is cleared to fly. I knew that then and I know it now. This situation is a great example of the exact reason to follow those restrictions. It is easy on VFR days to neglect the requirements set on an approach.Our responsibility to go missed when not in a normal position to land is an example of the value of following our procedures.
Air carrier First Officer reported receiving a GPWS terrain alert on arrival into BOI; followed by recognition of an unstabilized approach that resulted in a go-around.