The potential impact of introducing civil tiltrotors into the National Airspace System (NAS) has been the subject of several comprehensive studies dating back to 1987. CTRs are expected to successfully compete with fixed-wing aircraft provided a supporting infrastructure (ground facilities and air traffic control) is in place.
During 2001-2004, NASA sponsored or co-sponsored several studies of the Runway Independent Aircraft or RIA model of operations whereby existing stub runways could be used by VTOL operating in STOL mode in addition to operating in VTOL mode from vertiports. This operational concept has the potential to increase the capacity of the air transportation system. The increased capacity could then be used to increase throughput or reduce delay significantly throughout the system.
Correspondingly, in 2005, the NASA Heavy Lift Rotorcraft Systems Investigation examined in depth several rotorcraft configurations for large civil transport, designed to meet technology goals of the NASA Vehicle Systems Program. The investigation identified the Large Civil Tiltrotor (LCTR) as the configuration with the best potential to meet the technology goals. Additionally, since the studies of the late-1980’s and early 1990’s, recent events demonstrating the critical role of rotorcraft in disaster (man-made and natural) relief provide another compelling need for civil transport rotorcraft to be fully incorporated into the next generation airspace system.
In short, the role of advanced, high-speed rotorcraft designed for civil transportation should be re-visited to account for advances in rotorcraft technology, advances in airspace modeling, and the more prominent role of rotorcraft in public safety. Advanced civil tiltrotors, however, must be considered within the context of the Next Generation Air Transportation System, aka "NextGen".