Helicopter The Piasecki X-49 is a four-bladed, twin-engined, experimental compound helicopter under development by Piasecki Aircraft. The X-49A is based on the airframe of a Sikorsky YSH-60F Seahawk, but utilizes Piasecki's proprietary vectored thrust ducted propeller (VTDP) design and includes the addition of lifting wings. The concept of the experimental program is to apply the VTDP technology to a production military helicopter to determine any benefit gained through increases in performance or useful load. "SpeedHawk" is a concept aircraft[1] based on applying X-49A compounding concepts to a production UH-60 Black Hawk offering better performance, range, and increases in useful load. The "SpeedHawk" aircraft includes an SPU (third engine), high forward-swept wing concept, a 45 inch cabin extending fuselage "plug", and several other drag reducing and performance-oriented improvements, including a rotorhead fairing, landing gear streamlining, and a fly-by-wire flight control system. The U.S. Navy-sponsored project worth US$26.1 million consists of a Sikorsky YSH-60F helicopter modified by Piasecki as a testbed to validate the "Vectored Thrust Ducted Propeller" (VTDP) system. One YSH-60F was converted to test the feasibility of VTDP under an advanced technology demonstration program. The YSH-60F is powered by two General Electric T700-GE-701C engines. The demonstration contract was awarded on by the Naval Air Systems Command to Piasecki Aircraft. Piasecki installed a lifting wing with flaperons and a vectored-thrust ducted propeller (VTDP) to a U.S. Navy Sikorsky YSH-60F.[2] The compound helicopter technology added to the YSH-60F was first demonstrated in trials of the Piasecki 16H-1 and 16H-1A in the early 1960s, when the helicopters were flown at speeds up to 225 mph (360 km/h). The success of the Pathfinder inspired others to experiment with compounding, resulting in programs such as the AH-56 Cheyenne. In May 2003, the YSH-60F/VTDP demonstrator was redesignated the X-49A'.[3] During 2004, the X-49A VTDP program was transitioned from the US Navy to the US Army.[4] Piasecki planned to use the vectored-thrust ducted propeller design of the X-49 for their entry in the Future Vertical Lift program,[5] but were not chosen to take part in the Joint Multi-Role Technology Demonstrator (JMR-TD) phase.[6] The X-49A flight demonstrator is being developed with funding from the US Army's Aviation Applied Technology Directorate to demonstrate the ability to increase the speed of existing helicopters to 200 kt (360 km/h) or more.[7] The flight demonstrator has been updated with a lifting wing taken from an Aerostar FJ-100 business jet. A ring tail has been added and the helicopter drive train modified to accommodate VTDP. Piasecki conducted integrated tests of the modified drive train at the Navy's helicopter transmission test facility. The wings are intended to produce lift to offload the rotor so the rotor can be slowed down and produce less drag, allowing for higher speed.[8] The cockpit controls are modified with the addition of a manual prop pitch override on the collective for the ring tail. This is the only visible change to the aircraft's existing mechanical controls in the cockpit. The other controls needed to operate the compound helicopter's systems are integrated into the aircraft's existing mechanical controls to reduce pilot workload. The weight added to the X-49A demonstrator aircraft is estimated at about 1,600 lb (725 kg) due to the requirement[citation needed] to not modify the existing mechanical control system. The X-49A made its first flight on June 29, 2007[9] for 15 minutes at Boeing's New Castle County (KILG) flight test center.[10] This flight included hovering, pedal turns, and slow forwards and sideways flight using the VTDP for anti-torque, directional and trim control. The X-49A has completed its initial testing phase, and is continuing with further testing of the technology.[citation needed] Since then, it has flown over 80 flight events with more than 80 total hours logged.[citation needed] A helicopter is a type of rotorcraft in which lift and thrust are supplied by rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward, and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft would usually not be able to take off or land. The capability to hover efficiently for extended periods of time allows a helicopter to accomplish tasks that fixed-wing aircraft and other forms of vertical takeoff and landing aircraft cannot perform. The word helicopter is adapted from the French language hélicoptère, coined by Gustave Ponton d'Amécourt in 1861, which originates from the Greek helix/helik- (ἕλιξ) "twisted, curved"[1] and pteron (πτερόν) "wing".[2][3][4] English-language nicknames for helicopter include "chopper", "helo", "heli" and "whirlybird".

• published: 05 Feb 2014
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