Air carrier captain reported tower issued a low altitude alert on approach to jfk.

Attributes
ACN	1520489
Time
Date	201802
Local Time Of Day	0001-0600
Place
Locale Reference	JFK.Airport
State Reference	NY
Environment
Flight Conditions	Mixed
Aircraft 1
Make Model Name	Widebody Transport
Operating Under FAR Part	Part 121
Flight Phase	Landing
Route In Use	Direct
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Flight Instructor Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 110 Flight Crew Total 15770 Flight Crew Type 1475
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Inflight Event / Encounter CFTT / CFIT

Narrative:

While [being] vectored and set up for the ILS runway 04L at jfk; we were advised by approach that tower said we needed to land on the right side. I was then given direct to ebbee (FAF for runway 04R) and my first officer (first officer) had just completed entering the information and intercept in the FMC. The autopilot was engaged and approach was armed. The GS captured before intercepting the localizer inside FAF and the aircraft started to descend greater than normal. After passing through approximately 1000' I noticed I didn't have a GS indication and the first officer (first officer) asked tower if the GS had failed. By the time they responded we were too low (approximately 400'). I disengaged the autopilot and as I was initiating the go-around; tower was advising us to climb straight ahead to 3000' as were too low. After returning for another approach and landing without further incident; we noticed approximately 30 vehicles that were doing snow removal and had wondered if they had caused any interference with the navaids causing our aircraft to make a steep dive in order to capture the GS.

Original NASA ASRS Text

Title: Air Carrier Captain reported Tower issued a low altitude alert on approach to JFK.

Narrative: While [being] vectored and set up for the ILS Runway 04L at JFK; we were advised by Approach that Tower said we needed to land on the right side. I was then given direct to EBBEE (FAF for Runway 04R) and my First Officer (FO) had just completed entering the information and intercept in the FMC. The autopilot was engaged and approach was armed. The GS captured before intercepting the LOC inside FAF and the aircraft started to descend greater than normal. After passing through approximately 1000' I noticed I didn't have a GS indication and the First Officer (FO) asked Tower if the GS had failed. By the time they responded we were too low (approximately 400'). I disengaged the autopilot and as I was initiating the go-around; Tower was advising us to climb straight ahead to 3000' as were too low. After returning for another approach and landing without further incident; we noticed approximately 30 vehicles that were doing snow removal and had wondered if they had caused any interference with the navaids causing our aircraft to make a steep dive in order to capture the GS.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.