Beech A36 N902AT accident near Arundel, Maine

Probable cause

The pilot’s loss of situational awareness, which resulted in an unstabilized approach, descent below published minimum altitudes, and collision with terrain.

NTSB analysis

The pilot and passenger departed on an instrument flight rules (IFR) cross-country flight to the pilot’s home airport at the conclusion of a business trip. Weather radar imagery superimposed over the airplane’s flight track indicated that the airplane was flying toward an area of light intensity echoes associated with light rain to drizzle and instrument meteorological conditions as it approached the area of the destination airport. An AIRMET advisory for these conditions, as well as low-level turbulence, was valid for the accident time.

The pilot confirmed to the controller that he had obtained the most recent weather information at the destination and requested the RNAV (GPS) instrument approach procedure. The nearest airport with recorded weather observations, about 11 nautical miles west of the destination airport, reported 2.5 miles visibility, a broken cloud ceiling at 700 ft above ground level (agl), and an overcast ceiling at 1,000 ft agl about the time of the accident.

When provided vectors to the final approach course, and when issued his approach clearance, the pilot’s acknowledgements and read-backs of controller instructions were delayed by several seconds and incomplete. Automatic dependent surveillance – broadcast (ADS-B) track data indicated that the airplane flew through, then turned left toward, the final approach course. About 30 seconds after crossing the initial approach fix, about 200 ft below the minimum altitude, the controller issued the pilot a frequency change and provided a phone number through which to cancel his IFR clearance once on the ground. As the airplane proceeded parallel to and east of the final approach course, it continued to descend, and remained consistently hundreds of feet below the minimum published altitude for each respective segment of the approach. The airplane passed the final approach fix 750 ft below the minimum altitude at 58 knots groundspeed. The airplane continued to descend over the next .75 miles at a ground speed about 60 kts before the data ended in the vicinity of the accident site.

Several witnesses below the airplane’s flight path reported hearing the airplane, but stated that they could not see the airplane due to the low clouds, rain, and fog at the time of the accident. Their descriptions of the engine sound varied from “not normal” to “didn’t sound healthy” to sounding “…usual, just lower and louder.”

Examination of the accident site revealed severed tree trunks with clean, angular cuts, consistent with the engine producing power at the time of impact. Examination of the wreckage, as well as an engine test run, revealed no pre-impact mechanical anomalies that would have precluded normal operation.

About 8 months before the accident, the airplane was equipped with dual electronic flight instruments that functioned as the primary attitude indicator and directional gyro. These instruments were integrated with the airplane’s existing autopilot system. Review of the pilot’s logbook indicated that, after receiving about 2 hours of dual instruction, he had flown the airplane about 34 hours since the installation of the avionics, of which 7 hours was recorded as actual IFR.

The instrument meteorological conditions the pilot encountered during the approach to the destination airport would have resulted in a loss of outside visual references, requiring the pilot to rely on the flight instruments to maintain his intended course, altitude, and airspeed. The instrument conditions, likely turbulence, and increased workload imposed by beginning the approach phase of the flight presented a situation that was conducive to the development of spatial disorientation and a loss of situational awareness. Given that the pilot maintained a position east of the final approach course for most of the approach and far below the minimum published altitude throughout the approach, it is likely that he had lost situational awareness of the airplane’s position. No information was available to determine the modes or settings of the avionics and/or autopilot during the approach. Whether the pilot’s familiarity with the relatively new avionics and their interface with the autopilot contributed to the accident could not be determined based on the available information.

Text from the NTSB. Open the NTSB docket for ERA23FA006 for the full record.