CEN17FA248

A loss of control and subsequent in-flight breakup for reasons that could not be determined based on the available information.

The commercial pilot of the multi-engine airplane was conducting an instrument flight rules cross-country flight at night. The pilot checked in with air traffic control at a cruise altitude about 10,000 ft mean sea level (msl). About 31 minutes later, the pilot reported that he saw lightning off the airplane's left wing. The controller advised the pilot that the weather appeared to be about 35 to 40 miles away and that the airplane should be well clear of it. The pilot responded to the controller that he had onboard weather radar and agreed that they would fly clear of the weather. There were no further communications from the pilot. About 4 minutes later, radar information showed the airplane at 10,400 ft msl. About 1 minute later, radar showed the airplane in a descending right turn at 9,400 ft. Radar contact was lost shortly thereafter. The distribution of the wreckage, which was scattered in an area with about a 1/4-mile radius, was consistent with an in-flight breakup. The left horizontal stabilizer and significant portions of both left and right elevators and their respective trim tabs were not found. Of the available components for examination, no pre-impact airframe structural anomalies were found. Examination of the engines and turbochargers did not reveal any pre-impact anomalies. Examination of the propellers showed evidence of rotation at impact and no pre-impact anomalies. Review of weather information indicated that no convection or thunderstorms were coincident with or near the airplane's route of flight, and the nearest convective activity was located about 25 miles west of the accident site. Autopsy and toxicology testing revealed no evidence of pilot impairment or incapacitation. Given the lack of radar information after the airplane passed through 9,400 ft, it is likely that it entered a rapid descent during which it exceeded its design stress limitations, which resulted in the in-flight breakup; however, based on the available information, the event that precipitated the descent and loss of control could not be determined.

The Hennepin County Medical Examiner's Office, Minneapolis, Minnesota, performed an autopsy of the pilot. The cause of death was blunt trauma. Toxicology testing performed at the FAA Forensic Sciences Laboratory identified no drugs, ethanol, or carbon monoxide. Price County Airport (PBH), Phillips, Wisconsin, was located about 15 miles east of the accident site. The 0135, weather observation included wind from 360° at 3 knots, 10 statute miles visibility, a broken ceiling at 600 ft above ground level, temperature 14°C, dew point 14°C, and an altimeter setting of 29.86 inches of mercury. Regional weather radar did not indicate any convection or thunderstorms near to the airplane's flightpath. The accident site was located about 25 miles east of convective activity with no coincidental lightning. The pilot held a commercial pilot certificate with ratings for airplane single- and multi-engine land and instrument airplane. His most recent FAA second-class medical certificate was issued on August 11, 2016. The pilot's logbook was found in the wreckage. His total flight experience was 2,335 hours, with 463 hours of total night experience. No flight time was logged between October 21, 2016, and May 5, 2017. He had 11.2 hours logged within the last 60 days before the accident, with 1.7 hours of night time, logged on May 7, 2017. His first flight logged in the accident airplane was on September 29, 2015. He logged 70.4 hours total flight experience in the accident airplane, with 7.5 hours of night experience. His most recent flight logged before the accident flight was June 16, 2017, in the accident airplane. His most recent flight review and instrument proficiency check were completed on June 15, 2017. The pilot was the owner of the airplane. Review of the available airframe, propeller, and engine logbooks revealed that the airplane's most recent annual inspection was completed on September 25, 2015. An entry on the annual inspection document stated that, "aircraft checks satisfactory," and was signed by the pilot on October 10, 2016. No maintenance discrepancies were noted in the available maintenance records. The accident site was located within densely vegetated terrain intersected by a road, with debris scattered on either side of and along the road surface in an area with a radius about 1/4 mile. Tree scars and ground impressions indicated that the main section of the fuselage impacted terrain in a nose-low attitude. The fuselage was found upright and oriented northeast. Both wings were found separated outboard of their respective nacelles. The empennage was not attached to the fuselage and was located about 1,200 ft from the main wreckage. The distribution of the wreckage was consistent with an in-flight breakup of the airplane. Due to the dense vegetation, muddy terrain, and limited horizontal visibility of the accident site, a drone was used to locate parts of the wreckage that could not be found on foot. Figure 1. Wreckage Distribution The empennage was separated from the fuselage and located about 1,200 ft from the main wreckage. The rudder was found in three pieces and its trim tab was missing. Most of the vertical stabilizer was missing, except for the top 1.5 ft. The right side of horizontal stabilizer was found largely intact with its leading edge bent downward about 45°. The underside of the horizontal stabilizer exhibited wrinkling. Only a small portion of the right elevator tip was found, and the right elevator trim tab was missing. The entire left side of the horizontal stabilizer, most of the left elevator, and the left elevator trim tab were missing. The outboard portion of the right rear spar was found in the vicinity of the empennage components with no structure attached. The left engine, serial number 825104-R, was found separated from the airframe and completely submerged in a 9-ft deep crater about 75 ft east of the fuselage. A sump pump was used to reduce the water level in the crater so that the engine could be recovered. The propeller assembly for this engine was not visible and could not be examined at the accident site. A large portion of the engine nacelle was found in the same crater. The wreckage was recovered from the accident site for further examination. The left horizontal stabilizer; about 3 ft of the elevator and trim tab, and about 5 ft of the outboard left elevator and trim tab were not located. Cockpit The flap position could not be determined. The flap handle was found in the "UP" position. The gyroscope rotors for the #1 attitude indicator, #1 horizontal situation indicator (HSI), #2 directional gyro, and #1 turn-and-bank indicator were disassembled and examined. All rotors exhibited signs of spindle rotation. The landing gear and flap handles were both found in the retracted position. The left engine fuel selector handle was found in the right main tank position. The right engine fuel selector handle was found in the right main tank position. The right fuel selector valve was in crossfeed position. The left fuel selector valve was not observed due to impact damage. Fuselage The fuselage exhibited severe impact damage and was mostly in one piece with lateral and longitudinal tears in its skin from the forward pressure bulkhead to the end of the fuselage. The fuselage exhibited lateral tears in multiple places and a lateral tear along the right side. Eight seats were found installed in the aircraft. Left Wing The left engine nacelle was separated from the left wing about wing station (WS) 87 and WS 110. The left wing from WS 110 outboard was intact. The left wing's leading edge exhibited downward bending and diagonal creases in the area of WS 110 to WS 119. It exhibited upward bending at the trailing edge in the area of WS 110 to WS 119. About 2 ft of the inboard portion of the left aileron remained attached to the wing, and the outboard section of the aileron was missing. The left flap was connected to the nacelle via the push/pull rods, but the flap structure was missing. The outboard left flap track remained attached to the wing. The left speed brake was attached to its wing panel. The wing panel was attached to the wing. The left wing's nacelle was found with the left engine in a crater. Right Wing The right engine nacelle remained attached to the fuselage via control cables and wiring. Both wing spars were separated between the fuselage and the nacelle. The outboard portion of the right wing was separated about WS 110 and was intact. The right wing's leading edge exhibited downward bending and diagonal creases in the area of WS 110 to WS 119. It exhibited upward bending at the trailing edge in the area of WS 110 to WS 119. The right aileron separated from the wing in one piece. The right flap was separated from the wing and was not present. Both flap tracks were separated from the wing. The right speed brake was attached to its wing panel. Empennage The elevator trim tab actuator extension measured 1.8 inches, consistent with an approximate 10° tab up position. The right horizontal stabilizer was bent down parallel to the chord line about butt line (BL) 20. The right horizontal stabilizer exhibited diagonal creasing from the leading edge to trailing edge, inboard to outboard. The left horizontal stabilizer rear spar was attached from BL 0.0 outboard to BL 49; however, the left horizontal stabilizer structure from approximately BL 20 outboard was not found. Flight Control Cables Rudder control continuity was confirmed from the aft rudder bellcrank to the cockpit controls. Elevator control continuity was confirmed from the aft elevator bellcrank to the cockpit controls. Aileron control continuity was confirmed from the cockpit controls to the aileron bellcrank in the fuselage and to the cable separations in the wings. Both left and right aileron cables exhibited tension overload separations near their respective wing separations. Right Eng