N2356MRobinson Helicopter R22 BETA · 1993

On August 31, 2023, about 1525 eastern daylight time, a Robinson Helicopter R22 Beta, N2356M, was substantially damaged when it was involved in an accident near Kingston, New Jersey. The private pilot was fatally injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight.

The pilot was receiving flight training in the helicopter to upgrade his certificate level, and the pilot’s flight instructor stated that he had flown with the pilot for about 18 hours. The accident flight was the pilot’s second solo flight of their training, and the purpose was for the pilot to practice regular pattern work that did not include autorotations, only steep and shallow landing approaches.

The pilot took off from Princeton Airport (39N), Princeton/Rocky Hill, New Jersey, about 1520 according to witnesses and ADS-B data provided by the FAA. He departed the airport traffic pattern, even though the pilot’s flight instructor stated he was supposed to remain in the pattern. The flight instructor further stated that after reviewing the flight track, he thought it was odd, that the ground track looked “weird,” and that it was not consistent with what they briefed.

Shortly after departing the airport traffic pattern to the east, the helicopter climbed to 1,375 mean sea level (msl) then turned left on a north-northwest track of about 325°. The helicopter continued for about 1/2 mile before making a right 180° turn to the south on a track of about 185° for several miles before making a shallow right turn towards the Millstone River. An eyewitness who was located on the dam of the river was photographing wildlife. She observed the helicopter flying toward her and described that the helicopter was flying erratically as it approached her location; the helicopter was in a steep nose-down attitude about 1,000 ft above ground level. Seeing this, she held her finger down on the shutter release of her camera, which was equipped with a high magnification telephoto lens, and took 17 sequential photographs of the helicopter.

A review of the photographs confirmed the helicopter was spinning in a counterclockwise motion for several full rotations. While rotating, the helicopter made a series of aggressive pitch changes and rolls before the main rotor blades contacted the tail boom, severing the tail rotor assembly into three distinct pieces: the tail rotor blades and gearbox, the stabilizer, and the tail rotor drive shaft.

Selected photos are shown in figure 1, and are numbered in sequence as they were captured. Photo No. 1, showed the helicopter in a steep nose-low attitude. Photo No. 12 captured the helicopter leveling off and showed the pilot in the right seat. His left arm was visible, and his left hand appeared to be on the collective, albeit at an extremely high (increased pitch) position. The pilot was wearing a hard over-ear headset, but the left earpiece was down resting on his neck. Photo No. 13 showed the helicopter as it was in a right bank and rotating counterclockwise. At this point, the pilot was hunched forward at his waist and his right arm was clearly visible, but it is unknown if his hand was on the cyclic. His right earpiece was off. Subsequent photographs in the sequence showed the pilot bent almost fully forward at the waist, with his head on the forward windscreen and both sides of his headset around his neck; his sunglasses were off. His right elbow was resting on his right thigh, which was pulled back and bent at the knee. His hands and any associated control inputs to the cyclic or collective could not be observed. Photo No. 15 showed the severing of the tail boom and tail rotor assembly. During this sequence, the pilot continued to lean fully forward and both arms were pulled up; the photos do not indicate if he was holding onto the collective or cyclic.

Figure 1 – Select sequential photographs captured by the witness. The red and yellow oval annotations were added to obscure the pilot’s face.

The helicopter continued to descend, coming to rest inverted in about 3 ft of water on the shoreline of a tributary.

The pilot was an Israeli citizen and held and airline transport pilot certificate and airplane single- and multi-engine land ratings. He held a private pilot certificate with a rotorcraft-helicopter rating and had traveled to the United States to obtain a commercial pilot certificate in helicopters.

A review of maintenance records indicated that the last annual inspection of the airframe and engine was completed on January 13, 2023, at a helicopter total time of 7,033.7 and an engine total time of 4,831.30 hours; this simultaneously incorporated 50-hour, 100- hour, 300-hour, and 500-hour routine maintenance inspections and servicing. There was no documentation of any irregularity that would constitute a possible issue on the accident flight. Subsequent 50-hour and 100-hour maintenance was accomplished on May 8, 2023, June 11, 2023, July 14, 2023, and August 23, 2023, with no irregularities noted. The helicopter was returned to service as airworthy.

A review of maintenance records indicated that the last annual inspection of the airframe and engine was completed on January 13, 2023, at a helicopter total time of 7,033.7 and an engine total time of 4,831.30 hours; this simultaneously incorporated 50-hour, 100- hour, 300-hour, and 500-hour routine maintenance inspections and servicing. There was no documentation of any irregularity that would constitute a possible issue on the accident flight. Subsequent 50-hour and 100-hour maintenance was accomplished on May 8, 2023, June 11, 2023, July 14, 2023, and August 23, 2023, with no irregularities noted. The helicopter was returned to service as airworthy.

The helicopter fuselage containing the cockpit, engine, transmission, and main rotor blade assembly came to rest inverted in a water tributary about 3 ft deep, at an elevation of about 15 ft msl and was oriented on a heading of about 243°. Miscellaneous pieces of plexiglass, placards, a fire extinguisher, a partial tail rotor blade and tail boom fragments were discovered within 300 ft of the main wreckage in multiple locations. The section of the tail boom containing the tail rotor, drive shaft, and tail rotor blade assembly (as shown in Figure 2) was not located after several days of extensive searching. The main wreckage location was located about 200 ft east from the main body of the river and was surrounded by several tributaries with depths between 1 ft and 8 ft deep.

Figure 2 – Witness photograph depicting showing the portions of the tail rotor assembly that were not recovered.

Both main rotor blades remained attached to the main rotor head. Both blades had impact marks and gouges consistent with tail boom contact. The main rotor drive system gear box remained attached to the airframe with both left and right longitudinal pitch restraints separated from their respective stops. One pitch control link (PCL) was separated and had features consistent with overload; the opposing PCL remained attached. The pitch was manually actuated, and it was free of any binding.

The cyclic and collective push-pull tubes were traced to their respective control inputs and actuators. Fractures in the system were consistent with overload. Control continuity was confirmed for both collective and cyclic controls. The tail rotor pedals were impact fractured but manually traced through breaks in the control tubes to where the tail boom was separated.

Engine drivetrain and crankshaft control continuity were confirmed through 720° of manual engine rotation through the accessory section.

Both magnetos remained attached to the accessory housing. The right magneto was undamaged and sparked at all four leads. The left magneto capacitor was impact damaged and did not produce spark when rotated. Except for the No. 2 cylinder, the spark plugs displayed coloration consistent with normal engine operation when compared to the Champion Aviation AV-27 Check-A-Plug chart. The No. 2 cylinder top and bottom spark plugs contained blue staining.

The carburetor bowl was impact separated and severely damaged. The fuel inlet screen was unobstructed. About 3 gallons of aviation fuel with the color and smell of 100LL was drained from the inlet hose to the carburetor. There was no visible water or contamination discovered in the fuel.

The induction pipes were removed, and blue staining was observed in all four induction pipes.

The engine induction tubes contained a blue liquid residue and were sent to the NTSB Materials Laboratory for additional examination. A spectral library search was performed. These materials included anti-static materials, anti-corrosion materials, emulsifiers, gum preventatives, and dyes. These materials were commonly used as additives in aviation gasoline. Based on the spectral search information and the color of the material, the unknown mixture was likely weathered (evaporated) aviation gasoline.

There were no preimpact mechanical anomalies discovered on the recovered portion of the airframe or the engine that would have precluded normal flight or performance; however, the missing tail rotor was a crucial component that could not be examined due to its loss.

Postmortem toxicology testing on specimens from the pilot was performed by the FAA Forensic Sciences Laboratory; screening tests employed were for carboxyhemoglobin, ethanol, and a general drug screen, all of which were negative. An autopsy was not conducted. The pilot’s body was transported back to Israel after the accident.

Although the 44-year-old pilot was an Israeli citizen, he had undergone FAA aviation medical examinations. According to the FAA medical case review, his last FAA aviation medical examination was February 7, 2023. At that time, he reported no active medical conditions or medication use. He was issued a first-class medical certificate without limitation. A medical summary letter from an Israeli Aeromedical Examiner stated that, based on a search of medical documentation (outpatient visits, hospitalizations, laboratory tests and imaging results), nothing in the pilot’s medical history suggested risk of sudden incapacitation.