An Air Carrier Flight Crew got a terrain warning on the Expressway Visual to LGA Runway 31.
Synopsis
An Air Carrier Flight Crew got a terrain warning on the Expressway Visual to LGA Runway 31.
Narrative
We were on the EXPRESSWAY Visual to Rwy 31 at LGA. The arrival and approach were well briefed. We descended out of 2500 ft and proceeded down the EXPRESSWAY. As we approached the expected turn point (the highway configuration); I noticed that we were low for our position. I felt that if we turned at the proper point without further descent; we would be fine. I commented to the Pilot Flying that we were low for our position. I also noted the buildings past the turn point and thought that if there was any delay in the turn; they would be a factor at our altitude. At the turn point the Pilot Flying continued ahead with a slight descent. I immediately called for a turn and climb. The Pilot Flying reacted immediately to my call. During this flight path change we received a 'pull up' warning. I believe there was just one 'pull up' aural warning before it stopped. It was a 'bang bang' type situation; I.E.; 'We need to climb/turn;' power up/turn; 'pull up; pull up' stops. We quickly established a proper flight path and glide path and landed uneventfully. Nothing was said until we were at the gate. We discussed in detail what had happened and why. The Pilot Flying talked about fixation on things other than his altitude. The Progress page vertical speed and height below glidepath page was one of the distractions. We also talked about the requirement to execute the terrain avoidance maneuver. Neither one of us was 100% sure of the mandatory requirement during day VFR until we pulled out the FOM. We both now are very aware of the requirement. We also discussed what it would have been like to do this in New York airspace. I stressed the importance of proper altitude control during our visual approaches and in traffic patterns. We both felt our lack of familiarity with LGA in general and the 31 visual in particular was a factor.
Second reporter narrative
We were cleared the EXPRESSWAY visual RWY 31 at LGA outside of DIALS intersection. As a part of the approach briefing I briefed a visual pattern built into the FMC as a backup to the EXPRESSWAY Visual for vertical guidance using the plan view. (Rwy 31x-2.0nm-DIALS085/4-had previously measured distance to each intersecting point on charted visual.) We crossed DIALS; configured flaps 15 and landing gear down; airspeed 160 kts; v/s mode selected -1200 fpm. The FMC indicated we needed -1200 fpm. At 1300' AGL I called for flaps 30 (landing flaps) with autothrottles and autopilot still on. Reduced speed to 121 kts (Vtarget) and slowed to the v/s required on FMC which was 800 fpm. This is where I started to fixate on the FMC target descent rate of 500 fpm. From what I could see; looking at the Stadium; we didn't look low from my vantage point. A little confusion there. The Pilot Monitoring commented that we looked a little low. I slowed the descent rate to 600 fpm. Then I fixated on the airspeed because the autothrottles were letting the speed get slow; so I bumped it up a bit manually; letting it come back to speed on its own. By that time I missed the visual turn point over the highway configuration. The Captain at that point directed an immediate climbing left turn back to the runway. I initiated that climbing left turn; disengaging the autothrottles and autopilot. I glanced down at the FMC and it was showing us 200 ft low needing a 350 descent rate. At that point we received a 'pull up' warning. We quickly established flight path and glidepath once again. I called for the Before Landing Checklist and we landed uneventfully.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.