Spline
The concept demonstrators for the 280 (XV-15) and the SB1 (XH-59) were created and tested at the same time. Claiming the SB1 is behind because of the lead tilt rotors have in successful application is ignoring the facts. Both concepts were competed and the tiltrotor won. The 97 was suppose to be a risk reduction/confidence builder for SB1, but that proved to be a bust for those objectives.