History of Flight
On September 29, 2013, at 1109 eastern daylight time, an unregistered Mosquito XEL Helicopter was substantially damaged during a landing attempt at Lazy Springs Recreation Park in Felda, Florida. The non-certificated pilot, who did not hold a rotorcraft pilot certificate, was seriously injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local personal flight conducted under 14 CFR Part 91.
According to a witness, the pilot had trailered the helicopter to the park. After an uneventful takeoff, the pilot returned approximately 10 minutes later, deviating from his usual 30-to-45-minute flights. As the helicopter descended to about 30 feet, it appeared unstable and began oscillating side to side. The pilot aborted the landing and flew off, returning shortly after. On the second attempt, at about 30 feet, the helicopter began spinning to the left and impacted the ground. A postcrash fire ensued, and the pilot was pulled from the wreckage by the witness and another person before being airlifted to a hospital.
Personnel Information
The pilot did not hold any pilot certificate or rating for rotor-wing aircraft. He had completed a basic helicopter orientation course comprising 24 hours of ground instruction and 10 hours of flight instruction in a Schweizer 300C. Additionally, he had received instruction in a Robinson R22 and completed SFAR 73 ground training covering energy management, low rotor rpm, and mast bumping risks. He had approximately 20 hours of dual instruction and about 40 total flight hours at the time of the accident.
Aircraft Information
The Mosquito XEL Helicopter was of composite and metal construction, with a fiberglass airframe. It was powered by a 60-horsepower, two-cycle, two-cylinder engine with a 180-watt alternator. The drive train included a centrifugal clutch, cogged belt, and sprag clutch for autorotation. Manufactured in 2012, it initially weighed 314 pounds and was equipped with floats, qualifying it under 14 CFR Part 103 ultralight regulations. However, the pilot removed the floats and added an engine governor, placing it in the experimental category, requiring a private pilot certificate, FAA registration, and airworthiness inspection. The helicopter and engine had about 20 total operating hours.
Wreckage and Impact Information
The helicopter came to rest on a 15-degree embankment at the edge of a 27-acre lake, on a magnetic heading of 095 degrees. The cabin, seat, floor panel, and tail boom were largely consumed by fire. The rotor head showed marks consistent with mast bumping. Rotor blade A was delaminated and thermally damaged from the root to 5 feet outboard; its pitch change horn was bent 15 degrees upward. Rotor blade B was consumed by fire and delaminated, separated from the spar 13 inches outboard the root; its pitch horn was bent 45 degrees upward, and the pitch rod connector fractured in tension overload. Control continuity from pedals to tail rotor was verified, but cyclic and collective continuity could not be verified due to fire damage. The tail rotor blades moved freely. The engine was thermally damaged, with three of four motor mounts present; one retaining bolt sheared, and two others bent. The left landing skid showed thermal damage on the rear left side; the rear cross bow was fractured from bending overload.
Survival Factors
The occupant restraint system consisted only of a lap belt, which was latched. No shoulder harness or anti-dive strap was installed. The seat was not of an energy-absorbing design.
Tests and Research
A friend of the pilot reported a similar loss of control about two months prior, when the helicopter spun three times to the left during landing. The pilot told him that shutting off the automatic throttle governor allowed recovery. The engine governor and management system were mostly consumed by fire, preventing examination. The system included a servo module, control module, and twist grip throttle module. The governor worked by adjusting the throttle via a Bowden cable, requiring smooth, drag-free operation and proper DIP switch settings for gain, tachometer, and responsiveness.
Review indicated both flights displayed evidence of loss of tail rotor effectiveness (LTE), an aerodynamic phenomenon characterized by uncommanded rapid yaw toward the advancing blade.
Pilot's Statement
The pilot suffered serious injuries and memory loss, and was unable to communicate until June 17, 2015. He recalled sunny conditions and a mild headwind. He remembered lifting off, flying away, and circling back. During approach at about 40 feet, the helicopter suddenly spun twice, nosed over, and struck the ground. He could not remember mechanical issues and stated the previous spin might have been due to high speed and poor governor performance. When asked about cause, he said, "I would like to think it was the helicopter, but it could have been me."