Pilot Debrief

Maule M6 near Moose Pass, AK — 2019-06-29

Final reportANC19FA029
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Date
2019-06-29
Location
Moose Pass, AK, USA
Aircraft
Maule M6
Registration
N56512
Category
Airplane
Highest injury
Fatal
Fatalities
3
Phase of flight
Descent

Probable cause

The pilot's geographic disorientation and his exceedance of the airplane's critical angle of attack while maneuvering to avoid mountainous terrain, resulting in an aerodynamic stall.

NTSB narrative

The pilot was conducting a personal flight with three passengers aboard. The flight encountered an area of deteriorating visibility due to smoke from a wildfire burning in the area, and the pilot was attempting to follow a highway through mountainous terrain. The pilot-rated passenger stated that, as the flight progressed, forward visibility deteriorated and was "not very good at all"; she was able to see outside the cockpit only straight down. Further, a witness near the accident site reported 1/4 miles visibility about the time of the accident. The pilot-rated passenger stated that the pilot seemed stressed due to the deteriorating conditions and that the airplane occupants discussed locating an alternate destination. The airplane then entered an unusual attitude, and one passenger began yelling, "pull-up, pull-up" to which the pilot responded, "I've got this." The pilot-rated passenger's last recollection of the flight was the airplane entering an aerodynamic stall. GPS data from the accident flight revealed that, about 2 minutes before the accident, the airplane made about a 180° right turn and began a descent to a GPS altitude of 1,235 ft, followed by a left turn to a northerly heading and a climb to a GPS altitude of 2,032 ft and a groundspeed of 37 knots. The last recorded in-flight data point showed that the airplane was at a GPS altitude of 1,587 ft and at a 0- knot groundspeed. The on-scene examination revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The observed damage to the airplane indicated that it impacted the ground in a nose-down, near-vertical attitude, consistent with an aerodynamic stall. Given the passenger's account and GPS data, it is likely that, due to the restricted visibility conditions, the pilot became geographically disoriented, which resulted in the airplane's flight path toward rising terrain. It is also likely that the pilot subsequently initiated a sudden climb, during which the airplane's critical angle of attack was exceeded, resulting in an aerodynamic stall and impact with terrain.

Analysis

Primary failure mode
VFR into IMC
First missed decision gate
Pilot could have chosen to divert to an alternate landing spot earlier.

NTSB coding

Evidence available

  • Photos
  • 5 docket documents
View NTSB final reportView NTSB docket

Docket documents5

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