N31VA

HISTORY OF FLIGHTOn August 12, 2017, about 1649 eastern daylight time, a Bell 407 helicopter, N31VA, was destroyed when it was involved in an accident in Charlottesville, Virginia. The pilot and the observer were fatally injured. The helicopter was operated as a public aerial observation flight.

According to the Virginia State Police (VSP), the purpose of the flight was to provide the VSP command center with a continuous video downlink of the public demonstrations that were occurring in Charlottesville. The helicopter departed Charlottesville Albemarle Airport (CHO) about 1600. The helicopter arrived over the area of the demonstrations at 1604 and remained there until 1642 when the flight crew was tasked to provide overwatch for the Governor of Virginia's motorcade. At 1643, the flight crew advised the VSP command center that the helicopter was heading directly to the motorcade and was about 30 seconds away.

Radar data provided by the Federal Aviation Administration (FAA) indicated that, at 1648, the helicopter was flying at an altitude of about 2,200 ft mean sea level (msl) in the area of the motorcade. At that time, the helicopter was traveling north-northwest before it began to turn to the right and descend rapidly. Radar data indicated that, at 1648:30, the helicopter was descending at a rate of 6,800ft/min through 1,450 ft msl at a groundspeed of 30 knots. The helicopter then descended below the area of radar coverage, and radar contact was lost.

About 1649, a crewmember aboard a Fairfax County Police Department (FCPD) helicopter observed the accident helicopter descending upright into trees at a high rate of descent and then observed a "stirring" of debris. The crewmember advised the pilot, who immediately contacted the VSP command center to report that a helicopter had crashed. The pilot of the FCPD helicopter attempted to contact the accident helicopter but was unable to make contact with the flight crew. The FCPD helicopter pilot then landed near the accident site to render aid. The other two crewmembers exited the helicopter and proceeded to the accident site. Upon reaching the accident site, the crewmembers encountered heavy black smoke and fire.

The VSP interviewed 47 witnesses to the accident. Although their descriptions of the helicopter's altitude, direction of flight, and velocity varied, most witnesses reported that the helicopter, after initially hovering, entered a rolling oscillation, began to spin about its vertical axis, and descended in a 45° nose-down attitude while continuing to spin. Witnesses reported that they lost sight of the helicopter below the tops of the surrounding trees and then observed a plume of smoke rising from the area.

Video from a security camera located about 1.2 miles from the accident site captured images of the helicopter in a vertical descent with increasing vertical speed as the helicopter continued to descend toward the ground. Still photographs taken by a witness showed that the helicopter was spinning in a clockwise direction (when viewed from above the helicopter). PERSONNEL INFORMATIONThe pilot had been employed with the VSP aviation unit since 1999 and became the unit commander in December 2012. The observer had been employed with the VSP aviation unit since July 2017. AIRCRAFT INFORMATIONDuring this mission, the accident helicopter was configured with single main controls at the pilot's station and locked out pedals at the copilot (observer) station.

The accident helicopter's turbine engine had a full authority digital engine control (FADEC) system. The engine control unit (ECU) would continuously monitor the FADEC system for faults and would alert the pilot of any faults that could significantly impact engine performance.

The accident helicopter was also equipped with an airspeed-actuated pedal restrictor control system (PRCS), which reduces total left pedal travel at higher airspeeds by automatically adjusting the left pedal's forward stop. When the helicopter accelerates above 55 knots indicated airspeed (KIAS), the PRCS solenoid energizes, engaging a cam that limits forward travel of the left pedal by 25%, which reduces tail rotor blade angle from 25° to 17° When the helicopter decelerates below 50 KIAS, the PRCS solenoid de-energizes, which disengages the cam and enables full forward travel of the left pedal. METEOROLOGICAL INFORMATIONA sounding (a high-resolution rapid refresh model) for the accident site and time depicted a light and variable wind of 3 knots with clear skies over the accident site. No significant turbulence or wind shear was detected. AIRPORT INFORMATIONDuring this mission, the accident helicopter was configured with single main controls at the pilot's station and locked out pedals at the copilot (observer) station.

The accident helicopter's turbine engine had a full authority digital engine control (FADEC) system. The engine control unit (ECU) would continuously monitor the FADEC system for faults and would alert the pilot of any faults that could significantly impact engine performance.

The accident helicopter was also equipped with an airspeed-actuated pedal restrictor control system (PRCS), which reduces total left pedal travel at higher airspeeds by automatically adjusting the left pedal's forward stop. When the helicopter accelerates above 55 knots indicated airspeed (KIAS), the PRCS solenoid energizes, engaging a cam that limits forward travel of the left pedal by 25%, which reduces tail rotor blade angle from 25° to 17° When the helicopter decelerates below 50 KIAS, the PRCS solenoid de-energizes, which disengages the cam and enables full forward travel of the left pedal. WRECKAGE AND IMPACT INFORMATIONAccident Site

The main wreckage came to rest in an upright position along a magnetic heading of 333° in heavily wooded terrain that was adjacent to a residence. The main wreckage comprised the main fuselage (cockpit and cabin), aft fuselage, forward section of the tailboom, midsection of the tailboom (including the horizontal stabilizer), main rotor system, and engine. The main wreckage showed damage consistent with impact with trees and the ground. The main fuselage, aft fuselage, main rotor system, and engine were thermally damaged from the postcrash fire. The landing gear exhibited multiple fractures and a flattened appearance.

The aft section of the tailboom, containing the tail rotor gearbox, tail rotor, and vertical stabilizer, was found about 40 ft above the ground in a tree and about 100 to 150 ft south-southwest of the main wreckage. Debris from the fragmented tailboom was found in a debris field that spanned about 300 ft in length west of the main wreckage. Examination of the fragmented tailboom sections revealed multiple angled cuts consistent with main rotor blade contact.

Main Rotor System

The main rotor hub remained attached to the main rotor mast, and the four main rotor blades remained attached to their respective hub locations. For one of the main rotor blades, the pitch horn lug (for the pitch control link upper rod end) was fractured from its pitch horn. The pitch horn lug fracture surface exhibited signatures consistent with overload and thermal damage. Neither the fractured pitch horn lug nor the pitch control link upper rod end were found. The remainder of the major components of the main rotor system were found within or near the main wreckage site and exhibited fragmentation from impact and thermal damage.

The main rotor gearbox remained attached to the airframe. Drive continuity was established within the main rotor gearbox. The engine-to-transmission driveshaft was present, but its aft coupling was fractured.

Tail Rotor and Tail Rotor Drive System

Sections of the tail rotor drive system, from the steel tail rotor drive shaft at the forward end to the tail rotor gearbox input at the aft end, were recovered from the main wreckage, the debris field, and the aft tailboom section. Reconstruction of the tail rotor drive system revealed that most of the components were present except for the No. 3 tail rotor drive shaft, the forward portion of the No. 4 tail rotor drive shaft, and the hanger bearing between the Nos. 3 and 4 tail rotor drive shafts, which were not found. Fractures observed on the Nos. 1, 2, and 4 tail rotor drive shaft tubes were consistent with main rotor blade contact and were co-located with the angled cuts observed on the tailboom.

The tail rotor gearbox remained installed on the tailboom, and drive continuity within the gearbox was established. Residual oil was present within the gearbox, and the magnetic chip detector revealed no evidence of debris. The tail rotor remained installed on the tail rotor gearbox output shaft. Both tail rotor blades remained installed and were intact. One tail rotor blade displayed damage to its tip end, consistent with contacting the left side of the tailboom. The tail rotor blade leading edge also displayed a damaged area about 3 inches wide and about 15.5 inches inboard from the tip. The other tail rotor blade exhibited no anomalous damage.

Engine

The engine was found in the main wreckage lying on its right side near its installed location. All engine mounts had fractured in overload. The engine exhibited impact damage and was bent at an angle of about 30° at the junction of the turbine and gearbox modules. All major components for the engine were found at the main wreckage site.

The oil and pneumatic lines were manually checked and none showed evidence of looseness. The leading edges of the compressor impeller blades exhibited evidence of hard-body foreign object debris ingestion.

The ECU was found in the main wreckage near its installed location with one of its electrical connectors still attached. The ECU exhibited thermal damage due to the postcrash fire.

Flight Controls Systems

The three main rotor actuators were found in the main wreckage near their installed locations and exhibited impact and thermal damage. The main ...