Medium Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Training / Qualification; Distraction; Confusion; Situational Awareness
Deviation - Altitude Excursion From Assigned Altitude; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action; General Maintenance Action
Aircraft; Environment - Non Weather Related
We were being vectored for an ILS 13 into LGA. As we were being vectored at 2;000 FT MSL on a left downwind; the Captain's side radar altimeter was fluctuating. We then received the GPWS 'TERRAIN TERRAIN WOOP WOOP PULL UP' we executed the CFIT escape maneuver. We climbed to about 3;500 FT MSL. The warning stopped. I notified ATC of the warning and climb. They then cleared us back down to 2;000 FT MSL. The rest of the flight was uneventful. I am not sure if the radar altimeter was malfunctioning and that can cause that or if we truly were near the buildings over Manhattan. I never saw any red on the Terrain Display. But as we were on final I did notice that the high point was noted at 1;900 FT MSL. I wrote the GPWS up in maintenance book and Maintenance came out and tested it and found no problems. We proceeded on next flight with no warnings.
We were vector for left downwind for the ILS 13; at altitude of 2;000 FT at speed of 180 KTS; IMC conditions when we got the GPWS with the 'TERRAIN TERRAIN PULL UP.' I disengaged the auto pilot and climbed to about 3;500 FT or 3;000 FT. One let the Controller know of what happened. We got back to 2;000 FT and proceed for the approach.
An Air Carrier crew flying IMC at 2;000 FT MSL on a left downwind to a LGA Runway 13 ILS executed the escape maneuver to 3;500 FT MSL after the EGPWS alerted 'TERRAIN PULL UP.'