Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 70; Flight Crew Total 4092; Flight Crew Type 3887
Human-Machine Interface; Situational Awareness
Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Human Factors
Enroute ZZZ-San Salvador at FL390 we were able to ascertain through ATC Control that Runway 25 was in use and that we could expect to proceed via CAT VOR and execute the ILS Y 25. The FO (First Officer) was the Pilot Flying and thoroughly briefed the approach and his expectations for altitudes; automation modes and aircraft configuration throughout the approach. We were turned over to San Salvador Approach approximately 70 miles from the airport descending to FL200. San Salvador Approach cleared us direct CAT VOR; cross VOR above 5;000 [ft.] cleared ILS Y Runway 25. Both pilots confirmed clearance; altitudes and automation as we proceeded. As we neared CAT we were around 8;000 [ft.] at 240 kts.; still on the VNAV path. Although the FMC appeared to like the profile we both agreed it was time to slow down to meet the briefed approach profile. The FO selected vertical speed and dialed the speed back in the MCP window. With the selected vertical speed we weren't slowing down so I recommended Level Change. We slowed; configured and continued the approach passing CAT VOR. I set 2;500 [ft.] in the altitude window to fly outbound from the VOR as we completed the landing checklist. Once crossing the fix at [8.0 nm] we turned inbound via LNAV and set the FAF crossing altitude of 1;600 [ft.]; approach mode selected. We were in VFR conditions with the airport in sight on my side of the aircraft. As we turned towards the airport and descended I noticed we seemed low since we were more than 8 miles away and below the glide path. I looked back at the FMC and noticed fix [7.8 nm] with a crossing altitude of 2;500 [ft]. Shortly afterwards ATC asked what our altitude was and I replied 1;600 [ft.]. At that point both the FO and I realized we had missed [7.8 nm] on the procedure and should have crossed it at 2;500 [ft.]. [7.8 nm] is not clearly depicted on the approach plate with a crossing altitude nor is there an altitude depicted for the turn inbound. Also; we flew the procedure properly if the automation was in VNAV; but it wasn't. Although it was nighttime we were in VFR conditions with the airport in sight throughout the procedure. No GPWS cautions. At no time did I feel the procedure unsafe.
I was the PF.  CENAMER approach cleared us to descend out of FL390 to FL 200.  We were expecting the ILSY Rwy 25.  We briefed the approach thoroughly and I explained I would stay in VNAV until lined up on final approach where I would select APP for the ILS.   Well above FL200; we were handed off to ElSal approach.  They told us to proceed to CAT VOR and cleared us for a full approach ILS Y Rwy 25 approach with procedure turn.  HOWEVER; we were high before arriving at CAT so I selected to use vertical speed and open the speed window to control speed.  The CAPT suggested I use LVL CHG instead since it would do a better job getting down and controlling speed.  I did so; while  flaps and gear helped slow us.  I was still well above 3500'; over the VOR beginning the procedure turn outbound to D8.0.  Still in LVL CHG; We were able to fully configure and be on the VNAV PATH at 2500' at D8.0.  We completed the LANDING CHECKLIST.  At this point we had the airport in sight and never lost contact the whole time.  We were both using TERR MODE for obstacle clearance.  After passing D8.0 I asked the CAPT to select the next lower altitude of 1600' as depicted on the approach chart; and he did so.  In my haste to get at the correct altitude; slow down and  configure for landing; I did not  realize I had not reselected VNAV.  The autopilot descended us to 1600' as we turned toward final.  We crossed D7.8 at 1600' vice 2500'..  There was no GPWS warning and we had the airport in sight the whole time.  On final approach I selected APP and we noticed we looked low and at the same time; the control tower queried us about our altitude.  That was when we noticed our error but were already capturing the glideslope at that time.  We continued the approach; landed safely and taxied to our gate without further incident.
Captain reported a successful recovery of a CIFT event during approach as a result of temporary loss of Situational Awareness.