NTSB Factual Report

On June 27, 2002, approximately 1554 Pacific daylight time, a Seattle Aerotech Helipower 2500 experimental helicopter, N13RM, was substantially damaged during an emergency run-on landing and subsequently destroyed by fire following the rollover, which occurred during a 14 CFR 91 developmental test flight at Arlington, Washington. The commercial pilot, who was the helicopter's sole occupant, escaped the helicopter prior to the fire encroaching on the cockpit area and was not injured in the accident. Visual meteorological conditions were reported at Arlington at 1555, and no flight plan had been filed.

According to the FAA registry, the accident helicopter had received its initial airworthiness certification on May 2, 2002. In an initial telephone interview with the pilot, the pilot stated that the helicopter design, for which the accident helicopter was the sole prototype, is being developed by Seattle Aerotech for marketing as a kit. He reported that at the time of the accident, the helicopter had accumulated approximately 6 hours of hovering flight time and 28 hours of engine run time. The pilot reported that the flight test work being conducted at the time of the accident was focused on the helicopter's transition between hovering and forward flight. He stated that the helicopter had been experiencing significant vertical vibration when entering translational lift, and that in response to this problem, tracking equipment had been installed on the accident helicopter and the "B" blade of the helicopter's 2-blade main rotor had been adjusted upward 1/4 inch.

The pilot reported that on the accident flight, he initially performed a hover and 360-degree pedal turn without problems. He stated that he then entered forward flight at 10 MPH, and then transitioned back to a hover at 3 feet above ground level (AGL), again without problems. He reported that he then turned around and entered forward flight in the opposite direction at 6 feet AGL and 20 MPH, again without problems. He stated that he then turned around again and entered forward flight at 30 MPH. He reported that as he decelerated from 30 MPH back toward a hover, the helicopter experienced a violent vibration of sufficient severity that he felt an immediate run-on landing was necessary. During the run-on landing, the helicopter nosed down, the forward blade struck the ground and the aft blade severed the helicopter's tail boom. The pilot reported that he then saw a flash in the helicopter's engine compartment in his peripheral vision, and thus decided to egress the helicopter immediately. After the pilot egressed, the helicopter's fuel tank caught fire and the helicopter burned.

Post accident examination of the helicopter by personnel from the National Transportation Safety Board and Federal Aviation Administration disclosed no evidence as to the cause of the vibration or its origin.

NTSB Probable Cause

Aircraft control not maintained during a run-on landing. A vibration of unknown origin was a factor in the accident.