Regional Jet 200 ER/LR (CRJ200)
Flight Crew Air Transport Pilot (ATP)
Confusion; Distraction; Situational Awareness; Workload
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Executed Go Around / Missed Approach; Flight Crew Took Evasive Action
Aircraft; Company Policy; Procedure; Environment - Non Weather Related
While on the Expressway visual to Runway 31 at LGA we received what we believed to be an erroneous 'Obstacle' GPWS warning. We received this warning when on short final at approximately 200-300 FT above the water to the southeast of Runway 31. We were on the extended centerline and  approximately a 1/2 dot low on the electronic glideslope from the FMS as well as we momentarily had 3 red lights and one white light on the VASI. The First Officer (pilot flying) started to fly up and we got the GPWS warning. At that point the First Officer initiated the go-around. We complied with ATC's instructions and returned and shot the same approach without incident as well as without any GPWS warnings. It is worthy of noting that we were stabilized out of 1;000 FT. The biggest threat I see here from a flight crew and operational perspective is that there should be a charted RNAV visual approach in the FMS and on paper to fly for Runway 31 using the autopilot and constant angle (CANPA) procedures. While in our case; we were stabilized and on the glideslope; I have no doubt that if we had a charted and FMS based procedure that the margin of safety could be increased ten fold. Having to hand fly a dynamic charted visual approach procedure at night to an airport such as LGA is very workload intensive and requires expert airmanship. I believe that we could level the playing field by having an established and charted procedure.
A CRJ-200 crew executed a go-around from about 300 FT on final to LGA Runway 31 after the GPWS alerted an OBSTACLE warning.