The NTSB is looking at why the main rotor blades struck both the tailboom and the nose during the July 6 in-flight break-up sequence that destroyed Bell 525 FTV1 (flight test vehicle 1) and killed both test pilots. FTV1 was one of three 525 prototypes in the flight-test program, which has been put on indefinite delay in the wake of the accident. Scott Donnelly, chairman of Bell parent company Textron, said last week that the company remains committed to the program.

FTV1 was believed to be conducting tests at or near Vne speeds when main rotor rpms dropped off and the main rotors significantly "departed their normal plane of rotation," according to an NTSB spokesman. The Board also issued a brief preliminary report this week.

Flightradar24 shows the last data point for FTV1 was at 1,975 feet at a groundspeed of 199 knots. At the time, it was tracking south to north with a 20-knot tailwind, equating to an approximate airspeed of 179 knots. Bell’s projected high-speed cruise for the 525 is 162 knots. Dallas television station KXAS broadcast video from the scene that showed two large sections of the tailboom located 1,500 feet from the main wreckage impact site.

ENG helicopter pilot Ken Pyatt flew over the scene an hour after the accident and remained on site for an hour. He told AIN he saw “dozens of pieces of main rotor blade scattered quite some distance from the main crash site. We saw one entire main rotor blade that had been mangled, but you could see the attaching hardware, and in other places we found two- and three-foot sections of main rotor blades. That [rotor blade] debris field was over a quarter mile [behind] the impact site.” Pyatt said the debris trail was both left and right of the course line and started south of the main impact site.

The accident investigation will include copious data from real-time telemetry associated with the flight-test process, as well as the crew observations and video recordings from the chase helicopter, a Bell 429.