Date: 201910
Local time of day: 0601-1200
Location: LGA.Airport, NY
Flight conditions: IMC
Weather elements / visibility: 8
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Final Approach
Airspace: Class B N90
ATC / advisory: Tower LGA
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Anomaly: ATC Issue All Types; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem
Contributing factors: Procedure
Primary problem: Procedure

Narrative: We were on the ILS approach to Runway 04 at LGA. I was Pilot Flying; the FO (First officer) was Pilot Monitoring. The weather was overcast at about 900 feet; with approximately eight miles visibility. The approach controller had informed us earlier that we would be the last aircraft to land on Runway 04; but had not stated which runway they were switching to. I was hand flying the approach as required per the approach chart. Navigation setup on my side was green needles on the localizer; with the LGA VOR in DME hold; and I was listening to the Morse identifier on NAV 1. The approach was normal; with all checklists complete and the aircraft fully configured and at approach speed by 1500 feet AGL. At about 1200 feet AGL I heard static in my headset; but did not immediately recognize what it was. At about 1100 feet the FO called the runway in sight. I looked up briefly; but did not see it right away and so returned my attention to the instruments; and noticed that the CDI needle on the PFD (Primary Flight Display) had disappeared; and both LOC and GS in the FMA had red lines through them. The tower called us to ask if we had the airport in sight. I looked again; and this time I saw the runway clearly. We informed the tower that we did have the airport in sight; and they cleared us for a visual approach; which we accepted. At this point I realized that the static I had heard was a result of the localizer going offline and the Morse code being removed. The subsequent landing was uneventful. During the taxi-in; I noticed that the FO's PFD was displaying the identifier for the localizer to Runway 22 (mine was still in DME hold; so no identifier would have been displayed). I suspect that someone in ATC; either in the tower or elsewhere; had turned the Runway 04 localizer off in order to turn the Runway 22 localizer on (the two share a common frequency); and had done so before we had completed our approach. It is also possible that the localizer failed; though the appearance of the 22 identifier so soon afterward leads me to believe that this is not the case. Had this happened about 15 seconds earlier; we would have been in IMC with no vertical or lateral guidance; which is not a desirable state. As it was; we had just broken out of the clouds when the failure occurred.It took me a few seconds to associate the static in the headset with a NAVAID going offline; and I will be more alert to this in the future and more promptly execute a go-around. However; assuming that the localizer was turned off by ATC; they should be more mindful of who is on approach; and should not turn off the electronic guidance until the last aircraft for that approach has landed; especially in IMC. The low ceiling would have made going around off of the visual approach difficult to do had it been necessary.




Synopsis: Captain reported losing localizer signal while on final ILS approach to LGA.