Fatal Epic E1000 Crash Highlights Risks of Flying Advisory Glide Slopes Below MDA

A recent fatal accident involving a 2024 Epic E1000 turboprop at Steamboat Springs, Colorado, has brought renewed attention to the dangers of descending below the minimum descent altitude (MDA) while flying RNAV (GPS) approaches equipped with advisory glide slopes. The National Transportation Safety Board (NTSB) investigation is ongoing, but preliminary flight data reveals that the pilot descended below the published MDA while following an advisory glide slope, ultimately resulting in controlled flight into terrain near Emerald Mountain.

The aircraft departed Kansas City Downtown Airport late at night and was en route to Steamboat Springs Airport, a high-elevation mountain airport known for challenging approaches. The flight lasted roughly 2 hours and 20 minutes, arriving near midnight mountain time. The pilot elected to conduct the RNAV (GPS) Z RWY 32 approach—a non-precision approach featuring LNAV minimums—with an advisory vertical guidance glide slope depicted on the Garmin G1000 NXi glass cockpit.

Unlike precision approaches like LPV or LNAV/VNAV approaches, which provide obstacle protection down to decision altitude, advisory glide slopes on RNAV approaches only ensure obstacle clearance down to the MDA. Descending below MDA on such an approach exposes the aircraft to unprotected terrain, as was tragically demonstrated in this case. Although the primary flight display (PFD) presents the advisory glide slope in the same magenta-depicted format as precision glide slopes, the difference in protection is critical.

ADS-B data indicates the autopilot was engaged and coupled to the glide slope as the aircraft descended steadily along the approach course. Critically, the aircraft did not level off at the published MDA of 9,100 feet mean sea level (MSL), which was about 2,219 feet above ground level. Instead, it continued descending below MDA without the required visual cues of the runway environment, violating FAR 91.175(c) regulations. The last recorded altitude was 8,240 feet MSL, some 860 feet below the MDA and perilously close to the 8,250-foot elevation of Emerald Mountain, more than signifying a collision with terrain was imminent.

Two common pilot misconceptions contributed: first, that autopilots coupled to advisory glide slopes will automatically level off at MDA, which they do not; and second, that continuing descent below MDA on an advisory glide slope is safe if the aircraft remains on path. In reality, pilots must actively disengage glide-slope coupling or manually level off at MDA unless visual references for the runway environment are clearly established.

The chart for the RNAV (GPS) 32 approach includes cryptic notes regarding obstacles in the visual segment below the MDA and absence of the shaded clearance zone in the profile view, indications that terrain does penetrate the approach path below MDA. These subtle cues are critical for pilot situational awareness but often go unnoticed. FAA guidance advises pilots that while stabilized continuous descent on non-precision approaches is preferred, descent below MDA without clear runway visual references is prohibited.

This accident emphasizes the importance of understanding the fundamental differences between advisory glide slopes on non-precision RNAV arrivals and precision approach glide paths. The tragedy also illustrates how integration of flight automation without full comprehension of its limitations can lead to loss of terrain clearance. Until cockpit systems provide explicit alerts about obstacle exposure below MDA on advisory glide slopes, strict adherence to instrument procedures and visual minimums remains the sole safeguard.