Overview
A helicopter engaged in banner towing operations over a bay experienced a loss of control after the banner became detached. According to witness reports, the flight was proceeding normally until the banner fell away from the helicopter. Immediately following the banner's release, the helicopter began rotating to the right and subsequently descended into the water.
Witness Observations
Multiple witnesses observed the helicopter as it towed a banner offshore. They reported that everything appeared routine until the banner separated from the helicopter. At that moment, the helicopter initiated a right-hand rotation and descended into the bay. No further details about the helicopter's flight path or the pilots actions were provided by witnesses.
Investigation Findings
During the on-scene investigation, investigators examined the tail rotor drive system. They found that the retaining nut for the universal joint to yoke assembly on the tail rotor drive was not engaged with the threads, although it was still retained by safety wire. The safety wire was broken on the last twist prior to entering the hole used to affix the universal joint. Additionally, the solid drive pin located in the aft universal joint and passing through the drive shaft was missing.
These findings indicate that critical components of the tail rotor drive system were not properly secured or were absent. The disengaged retaining nut and missing drive pin would have prevented the tail rotor from receiving drive power, which is consistent with the loss of directional control observed after the banner fell free.
No other mechanical anomalies were reported in the investigation. The accident sequence—banner release, uncontrolled right rotation, and descent into the bay—aligns with a loss of tail rotor thrust.