B757 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 99; Flight Crew Total 16000; Flight Crew Type 3000
Situational Awareness
Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Human Factors
Cleared for approach to [JFK] RWY 4L; maintain 2000 until established. ILS signal was verified. LOC/GS engaged; as LOC began to come in but not yet captured; GS engaged and started down; LOC then captured. At that time we noticed a yellow line thru the GS and PNF queried ATC as to GS function. Aircraft continued to descend on autopilot and ATC informed us GS was functioning normally and minimum altitude was 1500 in this area; we were at 1200. We turned off the autopilot and climbed back to 1500. We were still just outside the final approach fix; reset LOC/GS and reengaged autopilot with good signals. The rest of the approach to landing was uneventful.
Just prior to intercepting the localizer for the ILS 4L into JFK; the crew was cleared for the approach while level at 2000 feet MSL. The PM armed the approach mode for the ILS and the glideslope appeared to be captured. Once on the course; the PM noticed there was no GS information and queried Approach Control as to whether the GS/Localizer was online. Approach Control stated that the crew was below the glideslope. PF immediately disengaged the autopilot/automation and climbed from approximately 1200 feet MSL to 1500 feet MSL; then leveled off prior to the Final Approach Fix. The aircraft captured the glideslope and at this time; Approach Control stated we were on glideslope and to contact Tower. From this point on the approach was executed without any further incident.
B757 flight crew reported descending 300 ft below the glideslope on approach to JFK.