NTSB Finds No Aircraft Anomalies in KSBS Accident

On February 13, the pilot and three passengers in an Epic E1000 were killed when their turboprop single hit Emerald Mountain—at about 900 feet below the approach minimum descent altitude (MDA)—near Steamboat Springs, Colorado. The accident happened just after midnight local time while the pilot was flying the RNAV (GPS) Z 32 approach to Steamboat Springs Airport/Bob Adams Field (KSBS), according to the NTSB preliminary report. Six days after the accident, the FAA issued a notam prohibiting pilots from using that approach procedure.

Four minutes before the accident, the metar weather for KSBS was a broken ceiling of 1,600 feet and overcast at 2,400 feet, with 10-mile visibility. The airport elevation is 6,882 feet, so those cloud layers would have been at 8,482 and 9,282 feet msl.

The RNAV (GPS) Z 32 nonprecision approach procedure has an MDA of 9,100 feet msl and prohibits a straight-in landing on Runway 32 at night. After flying that procedure, the only option would be to circle to land on Runway 14, and circling is allowed only on the airport’s northwest side. At the 9,100-foot MDA, the airport may have been obscured by the lower broken layer of clouds, which could have made it difficult to safely fly a circling maneuver, requiring that the pilot remain at the MDA and be able to see the runway and keep it in sight until the airplane is near enough to descend and land.

The NTSB preliminary report noted, “The waypoints in the data [from the aircraft’s Garmin G1000 avionics] were consistent with the RNAV Z RWY 32 approach…The last recorded altitude for the airplane was 8,221 feet msl, and the airplane’s autopilot was engaged.

“The wreckage was located in mountainous terrain about 3 miles south of SBS at an elevation of about 8,200 feet msl. A ground scar was found about 80 feet south of the main wreckage at an elevation of about 8,175 feet msl. The mountain peak is about 8,250 feet msl. The initial impact ground scars were aligned on an estimated 340-degree true heading. An odor consistent with jet fuel was present at the scene. Post-accident examination of the engine and airframe found no pre-impact anomalies that would have precluded normal operation.

“The RNAV Z 32 approach plate lists that the approach, both the circling and straight-in to runway 32, is not authorized at night. Additionally, the approach plate lists ‘Visual Segment – Obstacles.’

“At the time of the accident, there were two [notams] issued for SBS. One listed the runway end identifier lights (REIL) for Runway 32 unusable. The other listed the Precision Approach Path Indicator (PAPI) lights for Runway 32 unusable.”

After leveling off at the 9,100-foot MDA, the pilot would not have had the benefit of the Runway 32 REIL or PAPI, although that runway was not available for landing after flying the RNAV (GPS) Z 32 approach at night. The “Visual Segment – Obstacles” note on the chart was to inform pilots that there are obstructions that penetrate the obstacle identification surface between the MDA and the runway threshold. In other words, while descending from the MDA to the runway threshold, pilots should plan to avoid those obstacles.

Although the NTSB preliminary report does not say whether or not the engaged autopilot was tracking the LNAV+V advisory glidepath for that approach, that glidepath does intersect obstacles at the top of Emerald Mountain.

The FAA did not provide a reason for the notam prohibiting the use of the RNAV (GPS) Z 32 approach, but given the timing of its issuance, it may be a direct result of the accident. According to the agency, “The FAA issued a notice to airmen (notam) that the RNAV (GPS) Z approach procedure to Runway 32 is not authorized at Steamboat Springs Airport/Bob Adams Field (SBS) in Colorado. We are reviewing information shown on charts produced by non-FAA charting providers. This notam will remain in effect until non-FAA charting providers have corrected any potential charting issues. There are two additional public instrument approaches at SBS that pilots can use, so we expect this to have minimal impact to operations.”

As the airplane nears KSBS, according to the NTSB, “The controller cleared the pilot for the RNAV [(GPS)-E] approach to SBS. The pilot acknowledged the clearance but replied, ‘RNAV 32 to Steamboat Springs.’” The RNAV (GPS)-E approach is routed east of Emerald Mountain and has a circling-only MDA of 8,140 feet, with no restriction on which runway can be used.