Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 75; Flight Crew Total 2180; Flight Crew Type 1396
Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Unstabilized Approach
Flight Crew Took Evasive Action
Procedure
On approach into Boston; at night with visibility unlimited. We were initially cleared direct to RIPIT; the outer marker; and to descend to 2000 ft; on approach over the water to Runway 27. The altitude at RIPIT is charted at 1700 ft.With no traffic between us and the airport; we were then cleared direct RIPIT and cleared for the visual approach. My plan was to keep the speed up as long as I was comfortable and then slow a few miles outside of the outer marker but I did not want to be high and fast; thus causing an unstabilized approach. I turned off the auto pilot and auto throttles and was hand flying the airplane in a gradual descent of maybe 200-300 ft./min with approach mode armed and still in open descent however; almost all of my visual reference was outside and not referencing instruments or flight director. I had the runway in sight during the entirety of the approach however at some point; I completely lost situation awareness and ended up down between 900 to 1000 ft. AGL with the gear still up and 210 kts. My relationship to the outer marker when I 'captured this error' is unclear; as I stated my having lost situational awareness. I immediately leveled the aircraft at 1000 ft.; lowered the gear and slowed to flap speed and had an otherwise stabilized approach and landing on Runway 27 at Boston.Contributing factors to this incident would be flying into a 'black hole' and the visual references associated with that as well as fatigue. I did not feel fatigued at the time however; in recounting this incident and thinking about other small errors; such as missed radio calls; I do not think I was 'on the top of my game'. I did not realize this at the time otherwise I would have flown more conservatively. I had normal rest having been awake 12 hours and a duty start time of XA:00 with an event at XG:20.
A320 Captain reported descending out of assigned altitude during final approach; requiring evasive action.