Accident Details
On February 6, 2023, at approximately 2140 mountain standard time, a Bell OH-58A helicopter (registration N36FA) was substantially damaged during a 14 CFR Part 137 aerial application flight near Yuma, Arizona. The commercial pilot sustained minor injuries.
Flight Sequence
The pilot reported landing on a load truck at night to have the chemical hopper filled with 50 gallons of water for rinsing the applicator system. After departing from the load truck toward an open field about 200 yards away, while maneuvering at about 40 feet above ground level (AGL) with a speed near effective translational lift and about 80% transmission torque, the helicopter suddenly began to bounce and yaw. The pilot stated that when the spray tank was almost empty, the helicopter started to “bounce and tilt in all directions,” then “fish-tailed” before the engine lost total power.
Pilot Actions and Impact
The pilot arrested forward movement by pulling back on the control stick, leveled the helicopter, and lowered the collective. Unable to judge height above the ground, the pilot alternately raised and lowered the collective to control the descent. The helicopter landed hard in a dirt field. During the impact, a main rotor blade struck and severed the tail rotor driveshaft. The main rotor assembly, including the yoke and blades, separated from the mast and came to rest approximately 100 feet from the upright helicopter.
Aircraft Examination
The airframe had accumulated 9,629.8 hours at the time of the accident. Its most recent annual inspection was completed 8 months prior. Flight control continuity was confirmed from the cyclic and collective controls to the hydraulic servos and non-rotating swashplate, and from the anti-torque pedals to the tail rotor pitch control rods. Continuity was also established from the throttle twist grip to the fuel control and from the collective to the fuel governor. The master fuel valve lever was found in the ON position. Fuel was present from the airframe filter to the fuel spray nozzle.
A visual assessment indicated approximately 5 gallons of clean fuel remained in the fuel tank. The fuel quantity gauge, when energized, registered near zero and did not accurately reflect the actual fuel quantity. The fuel supply hose from the airframe filter canister to the engine fuel pump inlet was removed, and fuel dripped from the engine fuel pump after removal. The fuel pump operated normally when powered. A general inspection of the engine’s fuel, oil, air, and electrical connections, including B-nuts, showed they were tight and painted with torque stripe.
Engine Information
The helicopter was powered by an Allison M250-C20C (T-63-A720) turbo-shaft, gas-coupled free-power turbine engine. The most recent engine replacement was recorded in the logbook on October 18, 2022, about 4 months before the accident. The most recent 100-hour inspection was completed on December 27, 2022, at an aircraft total time of 9,573.8 hours. In a postaccident test run, the engine produced sufficient power and exhibited no evidence of mechanical malfunctions or failures that would have precluded normal operation.