The Piasecki X-49

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 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) .

General characteristics

• Crew: 3
• Capacity: 8 passengers or slung load of 6,000 lb or internal load of 4,100 lb for -B, -F and -H models and 11 passengers or slung load of 9,000 lb for -S
• Length: 64 ft 10 in (19.76 m)
• Rotor diameter: 53 ft 8 in (16.36 m)
• Height: 17 ft 2 in (5.23 m)
• Disc area: 2,262 ft² (210 m²)
• Empty weight: 13,648 lb (6,190 kg)
• Loaded weight: 20,110 lb (9,575 kg) (ASW mission)
• Max. takeoff weight: 21,884 lb (9,927 kg)
• Powerplant: 2 × General Electric T700-GE-401C turboshaft, 1,620 hp (1,208 kW) continuous each

Performance

• Maximum speed: 145 knots (167 mph, 268 km/h)
• Range: 380 nmi (437 mi, 704 km)
• Service ceiling: 19,000 ft (5,790 m)
• Rate of climb: 700 ft/min (3.6 m/s)
• Disc loading: lb/ft² (kg/m²)