Air carrier flight crew reported receiving two terrain proximity alert warnings while on approach to ROA Runway 24 even though they were reportedly 'well clear of terrain.'
Synopsis
Air carrier flight crew reported receiving two terrain proximity alert warnings while on approach to ROA Runway 24 even though they were reportedly 'well clear of terrain.'
Narrative
On approach to ROA we were cleared for the visual 24. We approached from the south side of the field and backed up the approach using the RNAV Y 24. Upon being cleared; the Captain decided to descend 3700 feet to match the final approach fix; giving us terrain clearance of 1;000 ft. We turned base between HIBAN and PROSE from the south and had another section of terrain to cross. It was while clearing this section that the terrain proximity alert occurred; stating 'Too low; terrain'. Upon hearing this; the Captain disconnected the autopilot and climbed to 4;000 ft; clearing the conflict. As the PM; I followed prompts from the Captain to set headings and descent rates to capture the final approach course while the Captain stabilized us. We then triggered the terrain proximity warning once more while intercepting the final approach course at 4;000 ft momentarily before being clear of all conflicts and joining the final approach course. The rest of the approach finished without incident; was stable; and we landed on Runway 24.Cause: Visual clearance on a terrain rich approach.Suggestion: Require instrument approach only acceptance on Runway 24 day and night instead of only at night.
Second reporter narrative
We were flying the visual to 24 in ROA. We were flying to intercept the inbound course between PROSE and HIBAN at 3;700. Approaching the ridgeline we received the GPWS. We were visual and well clear of terrain but climbed to 4;000 and the GPWS cleared. Approaching the top of the ridgeline; at 4;000; we received another GPWS and climbed until clear; and descended on the far side to re-enter the approach.Cause: The visual into ROA 24 while trying to prevent flying an excessive distance from the runway; given the approach altitudes; brought us close enough to the rapidly rising terrain to trigger the GPWS.Suggestion: Intercept further out on the approach; at a higher altitude.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.