Air carrier flight crew reported an autopilot programming malfunction resulting in loss of lateral and vertical guidance on an approach in mountainous terrain at night. The crew performed a missed approach then returned for another approach; and landed.
Synopsis
Air carrier flight crew reported an autopilot programming malfunction resulting in loss of lateral and vertical guidance on an approach in mountainous terrain at night. The crew performed a missed approach then returned for another approach; and landed.
Narrative
While on RNP M 15 into ASE prior to TRNGL; the RNAV E was activated prematurely causing a loss of lateral and vertical navigation while descending into terrain. This was unanticipated and my first thought was to execute a discontinue procedure; so I reached up to disarm the approach - which was already not active anymore. There was a moment where I struggled to decide what to do; as every discontinue procedure I had briefed had lateral guidance still existing in the FMS. I spent some time processing the situation; then executed a missed approach by pressing the Take-Off/Go Around button; calling flaps 2 and gear up. Since we were prior to the FAF we then set a higher altitude and used Heading mode to roughly follow the runway track while climbing at Vac; utilized Enhanced Ground Proximity Warning System on Primary Flight Display to avoid terrain; and then we began a right turn out to the missed approach holding point.We tried to reload the approach for lateral and vertical guidance; but due to time constraints were unable to do so safely. Our lowest altitude was above the DA; and we were not aligned with the runway to safely begin the balked landing procedure. We returned to center and received vectors to the IAF and repeated the approach with no further issues.Cause: Late night; long duty day; closed tower; and a complicated approach procedure. Suggestions: While it is probably unlikely to avoid this situation in the future; reinforcing the importance of briefing when the RNAV E is supposed to be activated would help to mitigate this in the future.Also; training reloading of the approach and sequencing the next point could be useful to allowing for a smoother go around/missed approach. Finally; briefing discontinue procedures with no lateral guidance would help if there isn't enough time to reload the approach safely to have a plan in place in the event of loss of lateral navigational guidance.
Second reporter narrative
During the approach phase at night with the approach/ tower closed; the RNAV-E (balked procedure) was inadvertently selected clearing the approach from the FMS along with lateral and vertical navigation. An attempt was made to reload the approach but due to the time constraint; was unsuccessful. A missed approach was initiated and the terrain mode on the Multi-Function Flight Display was used to assist to turn away from terrain while climbing over the airport. ATC was promptly notified and assisted with vectors once reaching ATC's area of responsibility back to the initial approach fix.Cause: Due to the uniqueness of the approach; duty time; ATC tower and approach being closed; and time of day the activation of the RNAV-E was made at the incorrect point of the approach.Suggestions: Prior to beginning this unique approach extra care in briefing the threat of the proper point to activate the RNAV-E at the correct time and noting crew awareness in respect to long duty days and higher workloads with the absence of ATC at night.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.