Perseverance pays off, and Piasecki Aircraft appears to be having some success with its X-49A “Speedhawk” – a Sikorsky H-60 modified with Piasecki’s vectored-thrust ducted propeller (VTDP). The attached video shows the helicopter has exceeded 170kt in flight testing.
The X-49A is flying at Boeing’s test centre in Delaware, and Dave Harvey on rotorhub.com, says the US giant is interested in combining the VTDP with the optimum-speed rotor technology from its A160T Hummingbird unmanned helicopter. That would make an interesting combination.Piasecki is a famous name in rotary-wing aviation, and has been working on compound helicopters for more than 40 years. The VTDP is a descendant of the “Ring-Tail” ducted propeller used on the Piasecki 16H-1 Pathfinder, which first flew in 1962. The Pathfinder utlimately achieved a speed of 225mph – almost 196kt for you fixed-wing folks.
After studying compounded versions of the AH-64 Apache and AH-1W SuperCobra, Piasecki persuaded first the Navy, then the Army to fund the conversion of an H-60 into a VTDP technology demonstrator (the X-49A is a Navy Seahawk painted to look like an Army Black Hawk). It took a while, but the “Speedhawk” finally flew in June 2007.
Replacing the tailrotor, the VTDP provides propulsion, anti-torque and flight control by vectoring the ducted propeller’s thrust. Piasecki believes compounding can overcome the limitations on helicopters, particularly when operating hot and high. Offloading the rotor with lifting wing and thrusting propeller allows the helicopter to fly faster and carry more.
The first phase of Speedhawk flights is limited to the existing Seahawk flight envelope, but after a drag clean-up (including rotorhub fairing and retracting gear) and installation of the third engine to help drive the VTDP, Piasecki plans to push the X-49A up to 200kt. That’s pretty good for a helicopter.