Date: 201605
Local time of day: 1201-1800
Location: ISP.Airport, NY
Flight conditions: VMC
Light: Daylight
Aircraft: Large Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class C ISP
ATC / advisory: Tower ISP
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Situational Awareness; Distraction
Anomaly: Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Automation Air Traffic Control; Person Flight Crew; Person Air Traffic Control
When detected: In-flight
Result: Flight Crew Took Evasive Action; Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Contributing factors: Environment - Non Weather Related; Procedure; Human Factors
Primary problem: Human Factors

Narrative: We were inbound to RIZER IAF for landing Runway 24 at ISP. Autopilot was engaged; Level Change was selected and Speed was selected at 210 knots. We were in LNAV to RIZER at that time; with about 5 to 6 miles to go. I think; but am not positive; that Approach Control had already handed us off to Tower. F/O called field in sight; and we were cleared for the visual approach to Runway 24 by either Approach or Tower (I don't recall if the handoff had been made at that time). We were in VMC conditions with unlimited visibility; and I had good awareness of the airfield; runway and all the surrounding terrain. Shortly thereafter; Tower told us to widen our turn to accommodate traffic ahead of us on short final. Used heading select to turnout about 40 degrees right; and extend our downwind/base leg. Meanwhile; aircraft was still descending (autopilot engaged still) to 1400 ft; which is the altitude for RIZER. As we were turning to final; FO made a statement that it looked like we were getting low. I was focused outside the aircraft at the time; visually watching terrain; the field; and the runway. On the FO's comment; I disconnected the autopilot and autothrottles; and continued the turn onto final. We were about three miles from RIZER. I noticed that our altitude was about 1200 ft and we simultaneously got a call from Tower to check our altitude; as they said they got a low altitude alert on us. We corrected back and continued visual approach and landing on Runway 24.When dealing with visual approach and possible arrival vectoring; we need to be especially cognizant of MSA's and or MVA's; and what we have set up the automation to do for us; prior to disconnecting the autopilot; and manually flying the aircraft. When things change on an approach (vectoring) we have to realize the automation may need to be changed to compensate for new conditions; or a total shift to manual control may be more appropriate.




Synopsis: Air carrier Captain reported descending to ISP Runway 24. While descending to cross the RIZER IAF at 1;400 feet they became distracted after ATC requested a turn for spacing. The First Officer recognized their low altitude just as ATC called with a low altitude alert.