Light Transport
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Inflight Event / Encounter CFTT / CFIT
Flight Crew Became Reoriented; Flight Crew Took Evasive Action
Airport; Environment - Non Weather Related; Human Factors
During our descent to approach at our destination; we made visual contact with the airport environment about 20 miles from the field. We received a clearance for a visual approach to the airport and began our descent to the runway. As we started our descent for the airport we both felt an urgency to increase our descent in order to be on a proper glide path for the runway. We increased our descent rate to order to do this; however we also attempted to match our descent rate in relation to the descending terrain below us as well. Our descent rate began to become greater than the slope; I noticed that we were getting closer to the down sloping terrain and became concerned with the possibility of GPWS issues. I requested that the flying pilot shallow out the descent to alleviate this threat and just as he was doing so; the GPWS gave out a momentary 'terrain/pull up' aural warning with no visual cockpit warnings present. Visual contact was still being maintained with the terrain; however we disconnected the autopilot and arrested the descent. There were no further warnings issued and the visual contact with the ground still showed us to have plenty of clearance and felt that this momentary warning resulted due to the rate of descent. We continued to configure our aircraft for landing and landed at our destination without further incident.We felt that the momentary aural warning was the result of an excessive rate of descent in conjunction with down sloping terrain. The setting sun in conjunction with some light haze may have played a part even though the visibility was reported as ten miles and the airport was in sight at twenty miles.One possible way to avoid such future events could have been to slow and configure the aircraft sooner in the descent and possibly use slight but gentle S-Turn maneuvers during the descent in order to continue to slow and allow time for the aircraft to arrive at a normal glide path without the use of a steeper descent rate that might result in a greater closure rate with the down sloping terrain.
Air Carrier Captain as the PNF; experienced a GPWS terrain warning during a day visual approach over downward sloping terrain. The PF shallows the descent and the warning immediately stops.