Civil Tiltrotor (CTR) aircraft have the unique operating ability to take off and land like rotorcraft and cruise like conventional fixed-wing aircraft. CTRs are capable of performing both vertical takeoff and landing (VTOL) and short takeoff and landing (STOL) operations. These unique capabilities give CTRs the flexibility to operate under a different concept of operations including runway-independent operations (RIO) using VTOL and STOL, or STOL at stub runways, to bring the traveling public to their destinations in a timely manner.

The assumption is that CTR fleet operations under RIO or using underutilized runways can directly increase the capacity to the National Airspace System (NAS) if major issues such as cost of new investment to the infrastructure and safety, and environmental issues such as noise and emission are justified by the value of such operations. Past studies have found there is potential for a CTR fleet to improve NAS capacity based on unique CTR unique attributes. Other studies investigating STOL operations have reviewed runway requirements, availability, and cost factors for operations in the NAS and in the New York and Washington Terminal areas, finding that a fleet of 40-passenger CTRs could reduce delay times in the NAS by replacing turboprop traffic with CTRs, providing CTR-specific runways can be developed.

From these studies, it is clear that for the CTR to realize its advantage over fixed-wing aircraft and rotorcraft, and to increase the NAS capacity and reduce delays, a noninterfering flight operation with CTR-specific stub runways, helipads, or vertiports is essential.

NASA Subsonic Rotary Wing researchers and several industry partners recently released a technical paper detailing a new study that focuses on the impact of CTRs on the NAS under the Next Generation Air Transportation System (NextGen). To develop a better understanding of this impact, the study took a high-fidelity approach to analyzing the flight performance of a CTR fleet in evaluating NAS performance. Three difference sizes of CTRs with seat configurations of 10, 30, and 120 passengers were developed using major Original Equipment Manufacturer design practices to assess the case for CTR operations in the NAS based on performance, market demand, and NAS capacity.

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