N911RW

On October 3, 2019, about 1503 eastern daylight time, a Bell OH-58A helicopter, N911RW, sustained substantial damage when it was involved in an accident near Fort Meade, Florida. The commercial pilot and the individual being rescued were not injured. The helicopter was registered to and operated by the Polk County, Florida, sheriff's office as a Title 14 Code of Federal Regulations Part 91 public-use flight.

The pilot was dispatched from Bartow Executive Airport (BOW), Bartow, Florida, about 1412 to provide aerial support for the pilot of a gyroplane who had made a forced landing in a phosphate pit and gypsum pond. The foliage in the gypsum pond was about 6 to 9 ft tall. The helicopter pilot stated that the gyroplane pilot was standing on his seat while holding onto the rotor blades. The helicopter pilot was concerned that the gyroplane pilot would sink into the gypsum, so he attempted to rescue the gyroplane pilot by having him grab the helicopter's right skid and then lifting him to safety.

The helicopter pilot anticipated that he would have to compensate for the change in the helicopter's center of gravity (CG) when the gyroplane pilot grabbed the skid. During the first two attempts, the gyroplane pilot was unable to hold on to the skid because his hands were covered in gypsum. During the third attempt, the gyroplane pilot had repositioned himself closer to the helicopter's right skid, and the helicopter pilot reported that, "without hesitation and without warning, [the gyroplane pilot] jumped up in the air towards my skid, grabbing the skid in the air, causing his entire weight to be forced onto my skid.” The helicopter pilot further reported that the helicopter’s CG had “immediately changed,” which caused the helicopter to descend and make “an abrupt and violent roll” toward the right.

The helicopter pilot immediately increased collective to prevent striking the gyroplane with the helicopter's skid but reported that the "roll was tremendous and without warning." The pilot tried to push the cyclic forward to increase speed and lift, but the helicopter continued to roll to the right and then impacted the gypsum pond, which resulted in substantial damage to the helicopter’s main rotor blades, tail rotor, and tailboom. The pilot reported no mechanical malfunctions at the time of the accident.

The Federal Aviation Administration's Rotorcraft Flying Handbook (FAA-H-8083-21) states the following about a helicopter’s lateral roll tendency, referred to as a “dynamic rollover”:

For dynamic rollover to occur, some factor has to first cause the helicopter to roll or pivot around a skid, or landing gear wheel, until its critical rollover angle is reached. Then, beyond this point, main rotor thrust continues the roll and recovery is impossible. If the critical rollover angle is exceeded, the helicopter rolls on its side regardless of the cyclic corrections made.

Dynamic rollover begins when the helicopter starts to pivot around its skid or wheel. This can occur for a variety of reasons, including the failure to remove a tiedown or skid securing device, or if the skid or wheel contacts a fixed object while hovering sideward, or if the gear is stuck in ice, soft asphalt, or mud. Dynamic rollover may also occur if you do not use the proper landing or takeoff technique or while performing slope operations. Whatever the cause, if the gear or skid becomes a pivot point, dynamic rollover is possible if you do not use the proper corrective technique.