Air carrier flight crew reported they were using the wrong altimeter setting while descending on approach which resulted in being below glidepath and a Caution Obstacle alert.
Synopsis
Air carrier flight crew reported they were using the wrong altimeter setting while descending on approach which resulted in being below glidepath and a Caution Obstacle alert.
Narrative
I was pilot monitoring. We were cleared for visual approach to runway XX to ZZZ. Backed up by the RNAV Z XX approach. Wx conditions: sky clear; XX nm vis; winds XXX XX gust XX. Wind shear advisory's in affect and reported within last 10 minutes. On approximately a 3 mile final we received a Caution Obstacle" annunciation. The captain who was flying immediately disconnected the auto pilot and momentarily leveled. Upon looking outside and verifying we were slightly below glide path per the PAPI we immediately corrected to on glide path via the PAPI and continued the arrival to an uneventful landing. Suggestions: The two main factors that played a role here were expectation bias as well as over focusing on wind/windshear allowing for a slightly low approach. The bigger issue was that upon correcting our descent to align exclusively with the PAPI and disregarding in aircraft glide path indicators we realized we had never been given and had therefore never updated the on field altimeter setting. We had been given an altimeter of 29.89 on initial contact with approach; but never had received an updated setting for the field which was reporting an altimeter of 29.77. This caused our low glide path into the airport and we should have caught it. I believe we missed it because we were over fixated on airspeed and expecting wind shear rather than looking at the approach as a whole. In summary I would say my biggest takeaways would be: 1. always double check altimeter setting on the field regardless of conditions and don't expect ATC to give it to you. 2. Don't let one adverse condition (in this case windshear potential) allow you to miss other equally important parts of safe operation"
Second reporter narrative
Very windy conditions with some sinking and climbing on final. We received an altimeter setting of 29.89 on the arrival but noticed the local altimeter setting on the ATIS was 29.77. I set 29.77 on the standby attitude indicator as a reminder but forgot about it. We never received a reminder for an altimeter setting by approach ever. We were in visual conditions with the airport in sight from about 10 miles and in. On final we were receiving gain and loss of 5-10 knots with the windy conditions. While we were on the approach on about a 3 mile final we received caution obstacle". While we had expectation bias to receive a windshear caution the obstacle caution was startling. I immediately disconnected the autopilot and went visual on the PAPI and only had to make a slight adjustment to get established on the PAPI the rest of the way in. After we landed we noticed our error with the altimeter setting and realized what happened."
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.