History of Flight
On September 21, 2013, at about 1150 mountain standard time, a Bell UH-1V helicopter, registration N22490, was destroyed when it impacted terrain near Cordes Lakes, Arizona. The in-flight separation of the main rotor hub and blade assembly preceded the impact. The owner/pilot and a non-pilot rated passenger were fatally injured. The personal flight operated under Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed.
The helicopter was based at Scottsdale Airport (SDL), Arizona, and had departed SDL that morning. Witnesses reported it landed at Sedona Airport (SEZ) for a fly-in event. After about two hours, the pilot and passenger re-boarded and departed SEZ. The helicopter air-taxied along runway 3 at about 100 feet above ground level, made a course reversal, and flew along runway 21 before leaving the area. Shortly after, eyewitnesses about 30 miles south-southwest of SEZ observed the helicopter "explode" and called 911.
Partial radar data showed the first target at 1138 at 6,500 feet, about 12 miles from SEZ on a magnetic bearing of 197 degrees. The last radar target at 1150 indicated 5,700 feet, coincident with the wreckage location.
The wreckage was distributed over about half a mile along the flight path. FAA and Honeywell personnel mapped the debris field, and the NTSB later completed the examination and recovered the wreckage for detailed analysis.
Personnel Information
The pilot held a private pilot certificate with airplane single- and multi-engine land ratings and received a rotorcraft helicopter rating in May 2013. He reported 1,856 total flight hours on his most recent medical application. His helicopter training and flight examination were conducted in a Hughes 269.
Recovered flight logs showed the pilot purchased the helicopter in Texas in April 2013 and received 1 to 2 hours of instruction there, though this was unconfirmed. He flew the helicopter to Arizona in seven legs totaling 9.6 hours, accompanied by a rotorcraft instructor with no UH-1 experience. Between the delivery and early May 2013, the pilot flew five flights with instructors totaling 8.3 hours. Subsequently, he completed 12 flights (13.4 hours) without an instructor. The last dated flight entry was August 4, 2013, followed by two undated entries. The pilot's flight examiner estimated he had less than 100 helicopter flight hours at the time of the accident; available records indicated about 33 hours in the accident helicopter make and model.
The Yavapai County Medical Examiner cited multiple blunt force trauma as the cause of death. A toxicology finding for ethanol of 1.470 mg/g was reported, but the laboratory could not determine sample handling conditions, leaving the possibility of putrefaction. FAA CAMI toxicology was negative for carbon monoxide, cyanide, ethanol, and all screened drugs.
Aircraft Information
The helicopter was manufactured in 1974 and equipped with a Lycoming/Honeywell T-53 turboshaft engine. It had a two-blade teetering main rotor (MR) system and a two-blade tail rotor (TR) system. The helicopter was originally US Army UH-1H, later converted to UH-1V medical configuration, then modified back to UH-1H, though civil registry still listed it as UH-1V. In July 2013, the FAA registered it as Experimental/Exhibition.
The most recent annual inspection was completed on April 20, 2013, signed off by the seller, stating the helicopter was in safe operational condition. Total time in service was about 3,664 hours at that inspection, and about 3,693 hours at the accident.
Meteorological Information
The automated weather observation at SEZ at 1135 included winds from 230° at 5 knots, gusting to 17 knots, visibility 10 miles, clear skies. Winds aloft near the accident location were from 210° at 15 knots at 6,000 feet and 220° at 18 knots at 7,000 feet.
Wreckage and Impact Information
The debris trail was oriented along a magnetic track of about 160°, covering about 3,200 feet from the northernmost to southernmost items. The main rotor assembly, including blades and hub, was located about 600 feet east of the debris trail. The main wreckage, including cockpit, engine, transmission, tail boom, and tail rotor, was in an impact crater at the southern end. No evidence of pre-impact failures of the engine, gearbox, transmission, or tail rotor drive was found. No fire or explosion was observed on debris trail components; fire was limited to the main impact crater.
Examination showed the MR hub and blade assembly separated as a unit via rotor mast fracture at the base of the hub. The mast fracture was consistent with overload, with no pre-existing corrosion or fatigue. Above the fracture, the mast exhibited contact with the hub static stops. The hub spring support assembly remained attached, but the hub springs were not installed. The stabilizer bar assembly was separated, with White side support fractures consistent with shear and bending overload.
Five components of the MR White blade control system were missing: pitch horn, pitch change link, stabilizer bar mixing lever, rotary damper assembly, and pitch control tube. Damage patterns indicated these were liberated by overload forces while the MR assembly was rotating.
The tailboom was fracture-separated from the fuselage due to overload. The engine, found separated from mounts, showed damage consistent with rotation under power at impact, with no pre-impact anomalies.
Additional searches failed to locate the missing White MR control system components.
Additional Information
Main Rotor Hub Moment Spring
FAA AD 2002-01-31 required removal of hub spring installations on certain UH-1 models. The accident helicopter had the hub spring support mount installed but the springs removed. The helicopter's AD compliance list indicated compliance, contrary to physical evidence.
Post-Purchase Pilot Maintenance Inquiries
The pilot contacted several knowledgeable persons for maintenance advice. His rotorcraft examiner examined the helicopter on May 6, 2013, and reported it in "fairly decent shape." The president of Helicopter Consulting (HC) briefly examined the helicopter and noted a tail fin spar AD not accomplished and a "bump kit" (hub moment spring assembly) installed. He later told the pilot the helicopter was "unsafe to fly." In August 2013, the pilot reported a "mast bump event" to an Overseas Aircraft Support representative, who cautioned him.
Others' Perceptions of Pilot's Attitude
Interviewees noted the pilot believed that Experimental registration allowed him to avoid maintenance requirements and comply with ADs as he saw fit. This attitude was considered a reduced concern for airworthiness.
Component and Maintenance Activities
The pilot purchased parts from a provider who sold components "as is." Emails indicated the pilot refilled a damper. Lack of detailed records prevented determination of maintenance history or part numbers.
FAA Ground Tracking Radar Information
Radar data from the PHX facility provided 58 returns from 1138:47 to 1150:10. The track was about 17 miles long, overlaid the debris path, and ended about 300 feet south of the main impact. Transponder altitude varied between 6,500 and 7,100 feet. Groundspeed averaged about 90 knots with irregular variations.
Mast Bumping Scenarios
The teetering-rotor design is susceptible to mast bumping, where hub contact with the mast can cause structural failure. The MR mast failure was consistent with a mast-bumping event, but the initiating event could not be determined from available evidence.