Date: 201510
Local time of day: 0601-1200
Location: JFK.Airport, NY
Flight conditions: Marginal
Weather elements / visibility: Cloudy
Light: Daylight
Aircraft: Large Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class B JFK
ATC / advisory: Tower JFK
Aircraft component: Elevator Trim System
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Human factors: Training / Qualification; Situational Awareness; Confusion; Distraction
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Person Air Traffic Control
When detected: In-flight
Result: Flight Crew Returned To Clearance; Flight Crew FLC Overrode Automation; Flight Crew Became Reoriented; Flight Crew Took Evasive Action
Contributing factors: Aircraft; Human Factors; Procedure
Primary problem: Procedure

Narrative: The 'MDA' was set in the altitude preselect instead of the 'stepdown altitude'.  We were flying as Co-Captains. My role was PIC and the other pilot's role was SIC. On this leg; I was the nonflying pilot and the SIC was the the flying pilot.  The weather at JFK was marginal VFR. ATC was using the ILS 4R and the RNAV GPS Y 4L approach. We were assigned the RNAV GPS Y 4L approach. Throughout our flight; I was privately admiring the proficiency; professionalism and airmanship of my Co-captain. He was doing an excellent job in the performance of his duties and his conduct of CRM. We conducted the CANPA procedure. As we approached the REPRE stepdown fix; the SIC called for the MDA altitude instead of the stepdown altitude. Since we were in VMC conditions; I set the MDA in the altitude preselect without verbal question. I do remember thinking; for just a flash of a second; 'Oh; he's having me set MDA; and he's going to mentally adjust the descent rate for KRSTL (the final approach fix)'. I then proceeded to observe the VMC conditions outside the airplane; especially noting the surface winds and the whitecaps on the ocean surface; and updated the SIC of my observations.During our descent; we received the 1000 foot call out from the radar altimeter and then the gear warning horn. We noted that as being out of the ordinary and lowered the gear. Shortly thereafter;  we received the low altitude alert from JFK tower. I advised the SIC that we were too low; at MDA and just approaching KRSTL (the final approach fix). About the same time; there was an autopilot trim caution message which the SIC corrected by disengaging the autopilot and retrimming the airplane. Being in VMC we remained at that altitude and continued for an otherwise uneventful landing. Even though both pilots were completely engaged in the approach and procedure; the assumption was; by both pilots; that the descent would be adjusted for the proper altitude at KRSTL (the final approach fix). Both pilots missed it. If the flying pilot would have called for the stepdown altitude instead of the MDA; 'AND'; if the monitoring pilot would have insisted on; or corrected; the altitude selection for the stepdown altitude; the whole altitude deviation situation would have been avoided.


Second narrative: Distraction caused by the PITCH TRIM caution message on approach.While Descending on the RNAV GPS Y to 4L; we began our descent from REPRE at 2000 thousand feet. And outside of the final approach fix KRSTL we descended below the clouds and proceeded visually to 4L. Shortly after breaking out of the clouds we received a PITCH TRIM Caution message; and with the caution message I noticed the aircraft begin to pitch up. I turned off the autopilot and got the trim under control. The aircraft was always stable. However due to the distraction we noticed that we had descended below 1500 before KRSTL. We were on the visual approach; so we corrected for the descent using the PAPI. We didn't descend below our minimums at anytime until we established the aircraft on the PAPI. We landed without incident and proceeded to the gate.


Synopsis: A air carrier crew flying a CANPA profile descent on the to JFK set the RNAV GPS 4L MDA. The crew; distracted by a PITCH TRIM caution; returned to the profile after ATC called a low altitude alert at less than 1;000 feet before KRSTL.