Accident Briefs: December 2017

Mackay, Idaho

The pilot reported that, while flying in mountainous terrain around 9,500 feet mean sea level (700 to 1,200 feet above the ground), the airplane encountered a downdraft. He added that he immediately turned away from the mountainside in a right turn, added full power, selected 10º of flaps, and pitched the nose up to maintain the airplane's maximum angle-of-climb airspeed (V_X). Subsequently, the airplane was unable to climb, and it then impacted wooded, snow-covered terrain along the mountainside.

The fuselage and both wings sustained substantial damage.

The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. The calculated density altitude near the flightpath was about 10,339 feet. According to the Federal Aviation Administration Koch Chart, the airplane would have experienced a 50% decrease to the normal climb rate. The high-density altitude conditions likely contributed to the airplane's inability to establish a climb.

Probable Cause: The pilot's decision to maneuver the airplane over mountainous terrain in high-density altitude conditions, which resulted in the airplane's inability to maintain altitude or establish a climb.

2 Fatal

Springfield, Ohio

Before takeoff on a personal cross-country flight, the private pilot received two official weather briefings of all the forecast and observed weather conditions along the flight route, which included thunderstorms and convective SIGMETs. A review of air traffic control (ATC) information revealed that, while en route to the destination airport, the pilot was in contact with ATC and attempting to circumnavigate oncoming weather and precipitation. The pilot requested ATC assistance and stated that he could avoid the clouds if ATC could help him avoid the precipitation, indicating that he was aware of the weather conditions but that he likely did not have onboard weather information. The Middletown sector approach controller provided two route options: one of the options would have allowed the pilot to completely avoid the precipitation and taken him farther away from his destination, and the other option would have allowed the pilot to proceed between two areas of precipitation and stay closer to his intended route. The controller obtained PIREPs from two pilots who had previously transitioned through the two areas of precipitation, and they reported that they "didn't really have any problems" flying through the area. The controller also provided the pilot the intensity of the two cells and the estimated distance between the two areas of precipitation. After the controller relayed this information to the pilot, he chose to fly between the two areas of heavy precipitation. The controller then transferred communication to the Urbana sector approach controller.

After the pilot checked in with the Urbana approach controller, the controller issued the pilot several heading suggestions to the northwest to avoid the precipitation, but the pilot responded that he wanted to continue on his present heading and then continued flying east toward the severe weather. Despite several subsequent suggestions by the controller to the pilot to change course to avoid the weather, according to radar data, the airplane continued flying east toward the severe weather. In the final 3.5 minutes of the flight, while flying east, the airplane made a left 360° turn while descending about 2,900 feet per minute (fpm), then resumed a climb while heading east. Less than 1 minute later, the airplane made a right 310° turn while descending about 1,200 fpm. The airplane then flew northeast and descended about 4,600 fpm to 3,440 feet above ground level. Subsequently, the descent rate increased to about 6,450 fpm, at which point radar contact was lost. The airplane entered an area of an outflow boundary and thunderstorms and likely encountered heavy precipitation, severe-to-extreme turbulence, updrafts and downdrafts, and wind shear.

A witness saw the airplane in a steep descent and heard the engine operating; the airplane then disappeared behind a tree line, at which point she heard the sound of an impact. The airplane impacted a corn field heading north. The vertical stabilizer and rudder were found 0.61 to 0.63 nautical miles southwest of the main wreckage, respectively, and exhibited overload signatures consistent with an in-flight breakup. A postaccident examination of the airframe and engine did not reveal any anomalies, other than the separated components, that would have precluded normal operation.

Although the Middletown sector controller provided general information about the observed weather, she did not provide specific information, such as the direction relative to the airplane and distance to the bands of weather and the widths of the weather bands, as required by Federal Aviation Administration Order 7110.65. The controller's workload did not prevent her from providing general weather information and suggesting headings to the pilot, which indicates that the controller could have provided more specific adverse weather information without detriment to other duties, as required. However, it is unlikely that this affected the pilot's decision about the route he flew. The pilot's continued flight into known thunderstorms resulted in the in-flight breakup of the airplane.

Although toxicology testing detected ethanol in the pilot's muscle and liver, the ratio of the detected ethanol suggested that some or all the ethanol was from sources other than ingestion.

Probable Cause: The pilot's decision to fly into known thunderstorms, which resulted in an in-flight breakup.