NTSB Factual Report

On September 25, 2017, about 1740 eastern daylight time, an experimental amateur-built, Mosquito XE 285 helicopter, N926KB, was substantially damaged when it impacted a residence in Odessa, Florida, during an autorotation. The private pilot sustained minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the local personal flight conducted under the provisions of 14 Code of Federal Regulations Part 91.

According to the pilot, he had departed from his residence in Odessa, Florida about 1645 for a local flight. He flew around the local area at an altitude of 800 to 1,000 ft above mean sea level, for about 45 minutes. During this time, there was no indication of any type of mechanical problem with the helicopter or engine. The pilot was returning to where he had departed from, and the helicopter was in a slow descent, when he noticed a substantial loss of engine and rotor rpm. He then tried to increase power with no response, so he immediately entered an autorotation and started looking for a place to land. He aimed for an open area, but "fell short" and the helicopter impacted the roof of a residence.

Examination of the accident site and wreckage by a Federal Aviation Administration (FAA) inspector revealed that the helicopter struck the back side of the roof perpendicular to the roof's peak. It came to rest on its left side with the cockpit on the forward side of the roof's peak, and the tailboom (still attached, but bent) on the back side of the roof's peak. The left landing gear skid had penetrated the roof into the attic and two other holes were also present in the roof, which corresponded to the location of the tips of both main rotor blades.

Both main rotor blades remained attached to the rotor head, and the tail rotor remained attached to the tail boom. The drivetrain and flight controls were intact; however, there was no indication of main rotor rotation at impact either on the main rotor blades or the roof surface.

According to FAA airman records and pilot records, the pilot held a private pilot certificate with a rating for helicopters. His most recent FAA third-class medical certificate was issued on January 28, 2016. He reported that he had accrued 79.8 total hours of flight experience, 18.1 of which was in the accident helicopter make and model.

According to FAA airworthiness and helicopter maintenance records, the helicopter's special airworthiness certificate was issued on April 20, 2017. Its most recent condition inspection was completed on that same date. At the time of the accident, the helicopter and engine had accrued about 20 total hours of operation.

The wreckage was retained for further examination.