Sikorsky S-97 Raider

Its top speed was over 260 knots but its excessive fuel consumption, vibration and complexity requiring the full-time attention of two pilots led to the program's cancellation.

First proposed in response to a Request for Information for the Armed Aerial Scout (AAS) program in March 2010,[6] the S-97 was formally launched on 20 October 2010.

[11] In September 2013, Sikorsky began final assembly of the first S-97 following delivery of the single-piece, all-composite fuselage by Aurora Flight Sciences.

At that point, the mostly-composite airframe was almost assembled, including some of the electrical wiring and avionics, missing elements were the transmission, drive train, engine, coaxial rotor, and pusher propeller.

[14][16][23][24] The S-97 design includes variable speed[2] rigid coaxial main rotors and a variable-pitch pusher propeller,[6][25] making the S-97 a compound helicopter.

The main rotors have hingeless hubs and stiff blades, to improve low-speed handling and efficiency of hover.

[4] Based on the technology from the Sikorsky X2 demonstrator, the prototype S-97s will be powered by a General Electric YT706 turboshaft (the same engine used on the MH-60M Black Hawk).

[28] Compared to the OH-58D Kiowa, the S-97 has significantly increased performance goals,[10] such as cruising speeds upwards of 200 knots while carrying weapons, turning at three times the force of gravity at 220kt, and a high hover efficiency (Figure of merit).

Toward the end of Phase 1 testing, software will be upgraded to Block 2, bringing in the propulsor and articulating tail to increase speed and enable the full flight envelope.

[needs update][33] On 2 August 2017, an S-97 prototype suffered what Sikorsky described as a hard landing at their flight test facility in West Palm Beach, Florida; both airline transport pilots received minor injuries.

[35] The NTSB factual report on the incident stated that the helicopter lifted into a low hover and immediately experienced excessive roll oscillations which lead to intermeshing of the counter-rotating coaxial rotor system, and a hard landing.

Video of the accident sequence showed aircraft roll oscillations exceeding 60–degree angle of bank during the course of 5 seconds, during which the upper and lower rotors collided at the 1 o'clock position.

Mockup in October 2011