Date: 201512
Local time of day: 1201-1800
Location: HDN.Airport, CO
Flight conditions: VMC
Light: Daylight
Aircraft: Medium Large Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class E ZDV
ATC / advisory: Center ZDV
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Second reporter function: Captain; Pilot Flying
Anomaly: Aircraft Equipment Problem Less Severe
Detector: Automation Aircraft Terrain Warning; Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action; Flight Crew Became Reoriented
Contributing factors: Aircraft; Environment - Non Weather Related; Human Factors
Primary problem: Aircraft

Narrative: It was the first flight of our trip and we were making our way into HDN. The first half of the flight went well and there wasn't any issues. As we were about to begin our descent into HDN we began to hear multiple aircraft setting up for visual approaches into HDN and ones on the ground attempting to depart. This is normal for this time of the year due to the heavy ski traffic in the mountains. On our approach into HDN we were cleared direct the field; which set us up pretty much on a straight in final for Runway 28; and left us a little higher until Center could get confirmation the [aircraft] ahead of us was on the ground. Once he cancelled we were given our visual approach clearance about 9-10 miles out at 11;000 feet and we set up for the straight in for Runway 28. During the Captain's approach briefing we did discuss the terrain that lies about 5 miles to the east of the runway and discussed clearing it at an appropriate altitude before descending towards the runway. Captain had the autopilot off and was visually flying the aircraft to the runway. During the descent over the terrain we received a 'Whoop; Whoop; Terrain; Terrain; Pull Up' call out that continued for approximately 10 seconds. The last time I remember looking at the PFD it showed us 1;300 feet on the radar altimeter and we were above 9;200 feet (1;000 feet above the higher of the two peaks). We both had visual contact with the terrain and when we received the alert we were already on the backside of the terrain that slopes down towards the runway and were in a position for a continued descent. Either way we proceeded to add power and began to climb away to ensure adequate separation with the terrain. Once the alerts had ceased the Captain lowered the nose and continued the descent into KHDN.I believe the reason for the alert was due to our rate of descent in close proximity to terrain. And if this was the case a more gradual descent with a maneuver or two towards the runway would have prevented this alert.


Second narrative: Flying a visual approach to Runway 28; we could see the airport from 40+ miles away; and our course was perfectly aligned with the runway. I input a 1;800 FPM descent to a point 3 miles from the runway and followed the VNAV down. This path CLEARLY kept us well above the ridge to the east of the field; visually it was quite clear that we would be well above it.As we passed over the ridge; we got a Terrain; Pull up warning; and I applied power and pitched the nose up to arrest the descent/climb. The warnings did not end until the airplane was leveled off; despite being well clear of the terrain visually. Both my FO and I remarked that there was no way we should have received any warning; let alone a 'pull up' warning.Once the warning ended; we gave it a couple seconds to ensure that we weren't crazy; and that we were clearly clear of the terrain; and began to descend again. The 'terrain; terrain' caution immediately began again; so I leveled the airplane off a little again; at this time we were passing over the ridge east of the airport; with nothing but a flat plain of ground ahead of us to the runway.Conferring with the FO that the warning was erroneous I continued and we landed uneventfully.The 10-7 pages include many notes about GPWS warnings for flights that fly a path north of the RNAV 28 course (which we did). But includes no guidance as to what to do with those warnings. Believing the warnings/cautions to be clearly erroneous; we did not fully execute an escape from terrain. I believe that the terrain model that the EGPWS is using is wrong; as being such a clear day both my FO and I were entirely confident that we were well above any terrain issues.If it had been remotely hazy; or nighttime not only would we not have accepted the visual approach; but we would have applied go around power and climbed back to MSA to ensure that we weren't wrong in our terrain clearance. The 10-7 pages definitely give the impression that GPWS warnings (including 'pull up') are expected on such a flight path; and thus permissible. The warnings that we received were as unexpected as a 'pull up' warning received at 24;000 feet.


Synopsis: Flight crew experienced a GPWS terrain warning at 9;200 feet during a day visual approach to Runway 28 at HDN. The crew leveled off momentarily and believe the descent rate caused the erroneous warning due to the 8;200 foot hill 5 NM to the east.