Event Overview
On 28 August 2017, at approximately 10:15 a.m., a Schweizer 269 helicopter (registration 4X-BIM) crashed during a hover test at Herzliya Airport, Israel. The helicopter, operated on a private flight, had just completed a two-hour flight and returned to the airport. After landing, the pilot felt vibrations in the cyclic and skid, prompting a brief hover test to assess the issue. During the test, the helicopter began to vibrate intensely, descended, and broke apart upon ground impact.
Flight Sequence
The day began at 07:30 when the pilot and a passenger (the owner) departed for a training flight in the Sharon area. They landed at Ein Vered for breakfast, then returned to Herzliya at 10:14. During the landing, the pilot noticed a slight vibration. After shutting down and inspecting the helicopter visually (including dampers), he restarted the engine and performed a hover at about 20–30 cm (1 foot) above ground. The hover was initially stable, but during descent for landing, vibrations escalated rapidly. The helicopter bounced, yawed left, and became uncontrollable. The pilot shut off the throttle and mixture. Within seconds, the main rotor and mast separated. The pilot and passenger evacuated unaided and were treated at Meir Hospital, released after a few hours.
Witness Observations
Eight witnesses, including pilots and mechanics, reported seeing the helicopter vibrate violently in the air, with forward-aft and lateral oscillations. Several heard an unusual noise, described as a metallic crunch or gear-like sound. The helicopter descended, hit the ground, and disintegrated with parts scattering.
Damage and Injuries
The helicopter was substantially damaged and declared a total loss. The pilot and passenger suffered minor injuries.
Investigation Findings
Detailed metallurgic inspections of the main rotor components, including dampers and mast, were conducted at the NTSB materials lab and the manufacturer's lab. The investigation focused on the lead-lag phenomenon and ground resonance. No explicit probable cause was stated in the report.