Robinson R-44 Raven II | N323TT

The DTSB determines the Probable Cause of this accident to be Pilot Error, in that the pilot did not ensure proper safe maneuvering flight during the flight from Ellensburg Washington to Coeur d’Alene upon approaching the face of upsloping rising terrain at approximately 3000 feet MSL. The aircraft descended and turned, likely to observe something of interest on the ground. In the process of suspected aggressive maneuvering, the tail boom was struck by the blades. The debris field was 340 feet long and and began with tail rotor debris located at 2182 feet MSL. A fire or explosion was associated with the impact. The mast bump phenomena is highly likely due to previous mast bump losses in this similar type aircraft, and as aggressive maneuvering below sufficient rotor RPM can cause main blade flapping and a catastrophic intersection of the rotating blades with the tail boom.

The DTSB recommends that all pilots of all rotorcraft become familiar with the concept of mast bumping, and condition themselves to avoid the conditions and aggressive maneuvering that can allow it to occur.