History of Flight
On January 8, 2013, about 1225 Pacific standard time, a Bell OH-58C helicopter (N911PT) collided with terrain near Riverdale, California. The commercial pilot was the sole occupant and sustained serious injuries. The helicopter sustained substantial damage to the forward fuselage, tail boom, and rotor assembly. The helicopter was registered to Blair Helicopter Services, Inc., and operated under 14 Code of Federal Regulations Part 137 for agricultural aerial application. Visual meteorological conditions prevailed, and a company flight plan had been filed.
The pilot was conducting spray operations when he experienced a flight control system anomaly described as a lateral rolling tendency to the right. After finishing an application run, the pilot ascended in an effort to return to the operator's base for repairs. The helicopter progressively became more difficult to control. The pilot diverted to a nearby company loader to land, but the helicopter continued to roll right and did not fully respond to left cyclic control inputs. The right rolling tendency persisted, and the helicopter collided with terrain.
The operator reported that the helicopter impacted terrain in a right-side low attitude and bounced before coming to rest about 10 feet beyond the first identified point of contact.
The pilot was transported to a nearby hospital.
Personnel Information
The pilot, age 61, held a commercial pilot certificate with a helicopter rating and a second-class airman medical certificate issued December 28, 2012. The operator reported 30,000 total flight hours, including 20,000 hours in helicopters and 3,000 hours in the accident make and model. The most recent flight review was completed December 10, 2012.
The pilot obtained most of his aerial application knowledge through on-the-job training. He attended the Professional Aerial Applicators' Support System (PAASS) training in 2013 and held a California chemical applicators license.
Aircraft Information
The helicopter (serial number 66-20356) was manufactured by Bell Helicopter in 1971 and delivered to the U.S. Army on December 27, 1971. It was retired from military service and issued an FAA restricted category airworthiness certificate on November 24, 2008. At conversion, airframe total time was approximately 3,553 hours. The helicopter accrued about 1,894 hours from civilian certification to the accident.
Maintenance records showed an annual inspection completed November 20, 2012, at 5,426.1 airframe hours and 5,059.7 engine hours. Airframe total time at accident was 5,443.8 hours.
The helicopter was equipped with an IsoLair agricultural spray system, including a 130-gallon belly-mounted fiberglass tank and a symmetrical spray boom spanning about 29 feet.
Examination Findings
Representatives from the NTSB, FAA, Arrow Falcon, and the operator examined the recovered airframe, flight controls, and hydraulic systems at the operator's hangar in Lemoore, California.
The flight control assembly examination revealed that the gas producer throttle control cable was entwined with adjacent flight control push-pull tubes. A section of the cable appeared pinched between the lower mixing lever unit and tunnel partition wall. Multiple nylon loop cable clamps securing the throttle cable to the vertical tunnel partition were broken and separated. The cable's plastic outer sleeve showed signs of chafing, exfoliation, dimpling, distortion, bunching, crushing, gouge marks with black discoloration, and splits exposing the internal stainless cable.
It was not determined whether this damage resulted from wreckage recovery efforts or was a preexisting condition.
Hydraulic actuators were examined at Woodward HRT facilities. The left and right cyclic actuators functioned normally with no excessive external fluid leakage. The collective actuator sustained impact damage and could not be functionally tested.
Additional Information
Maintenance records indicated an annual inspection completed November 20, 2012. The manufacturer's Inspection Guide established inspection requirements for continued airworthiness. Relevant excerpts include inspection of cyclic control freedom and condition of boots and grips (2.13) and inspection of throttle control cable assembly for condition and security (2.14.F).