Accident Sequence
On January 8, 2019, about 1000 central standard time, a Robinson R44 II helicopter, registration N484AB, experienced a hard landing during an autorotation shortly after takeoff from Garner Field Airport in Uvalde, Texas. The helicopter was engaged in a local instructional flight under Title 14 Code of Federal Regulations Part 91, operated by a private individual. Visual meteorological conditions prevailed, and no flight plan was filed.
According to the flight instructor, all pre-takeoff checks were normal. After the helicopter passed through effective translational lift and reached about 40 knots airspeed, the collective was raised to increase power to the takeoff setting. Shortly after, a loud pop or bang was heard, followed by an uncommanded right yaw and severe vibrations. Due to the low altitude and airspeed, the instructor immediately initiated an autorotation. During touchdown, the helicopter tilted forward, bringing the main rotor blades about 6 inches from the ground. The instructor applied aft cyclic to correct, causing the main rotor blades to contact the tailboom.
Damage and Examination
The helicopter sustained substantial damage. Postaccident examination revealed the tailboom was partially separated and the tail rotor driveshaft system was damaged. The clutch assembly lubricant was drained, revealing an unusual amount of metallic debris in the strainer. The clutch assembly was removed and sent to Robinson Helicopter Company for further examination.
Disassembly of the clutch assembly showed galling of the sprags and the corresponding sprag contact surfaces on the shaft and hub. According to the Robinson R44 maintenance manual, clutch assemblies require inspection for metallic flakes every 500 hours. The most recent inspection of the clutch assembly had been completed on April 18, 2018, approximately 245 flight hours before the accident.