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Compound Helicopter

By Graham Warwick

 

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SpeedHawk has wings and tail-mounted variable-thrust ducted propeller

Trials to start using Piasecki-modified Sikorsky H-60 helicopter planned to achieve speeds of up to 200kt.

Piasecki Aircraft is preparing its X-49 experimental compound helicopter for a first flight before the end of June.

The modified Sikorsky H-60, with wings and tail-mounted variable-thrust ducted propeller (VTDP), has been moved to Boeing's Wilmington, Delaware facility for ground and flight testing.

Dubbed the SpeedHawk by Piasecki, the X-49 is being developed with incremental funding from the US Army's Aviation Applied Technology Division to demonstrate the ability to increase the speed of existing helicopters to 200kt (360km/h).

The VTDP replaces the tail rotor and provides thrust for forward flight, while the wing unloads the rotor and allows the helicopter to fly faster.

Initially the aircraft will be flown within the SH-60's existing flight envelope, but the company then plans to install a third engine and push the helicopter to 200kt, says vice-president John Piasecki.

In forward flight most of the more than 2,100shp (1,560kW) from the two main engines will go to the VTDP, says Piasecki.

The third engine, called a secondary power unit, will replace the existing auxiliary power unit and provide another 600-700shp to the ducted propeller to push the compound helicopter to higher speed.

"This technology gives the helicopter the ability to productively use the extra power in forward flight," says Piasecki.

"Traditionally we add power to lift more, but we are at the outer edge of the envelope on the H-60, where a marginal increase in weight brings a significant reduction in forward speed."

This is because the heavily loaded rotor stalls at higher speeds.

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"The UH-60 is a 90kt helicopter in Afghanistan," claims Piasecki. "The power that goes into the high/hot hover cannot be used in forward flight."

While the SpeedHawk wing and tail add weight and download, "the aircraft has adequate margin in the hover to carry the payload, then can harness the power to fly at 200kt", he says.

Funding permitting, Piasecki plans about 100h of flight testing in the X-49 programme's first phase.

Funding to install the SPU and perform a nine-month drag clean-up for high-speed flight testing, which includes fitting retractable gear and a rotor-hub fairing, has yet to be secured.
 

Global Flight

 

 

Sikorsky Piasecki X-49 “Speedhawk”

- First Flight in June

 June 3rd, 2007 in Aviation News, Military and Helicopter.

 

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Piasecki Aircraft is preparing its X-49 experimental compound helicopter for a first flight before the end of June.

The modified Sikorsky H-60, with wings and tail-mounted variable-thrust ducted propeller (VTDP), has been moved to Boeing’s Wilmington, Delaware facility for ground and flight testing.

The X-49A “Speedhawk” is an experimental helicopter currently under development. It is the subject of a $US 26.1-million U.S. Navy-sponsored project that consists of a Sikorsky YSH-60F helicopter modified by Piasecki as a testbed to test the “Vectored Thrust Ducted Propeller” (VTDP) system. One YSH-60F will be converted to test the feasibility of VTDP under an advanced technology demonstration program. The YSH-60F is powered by two General Electric T700-GE-401C engines.

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The demonstration contract was awarded in October 2000 by the Naval Air Systems Command to Piasecki Aircraft. Piasecki will install a lifting wing with flaperons and a vectored-thrust ducted propeller (VTDP), or “ring tail,” to a U.S. Navy Sikorsky YSH-60F.

The compound helicopter technology that will be added to the YSH-60F was first demonstrated in trials of the Piasecki 16H-1 and 16H-1A in the early 1960’s, when the helicopters were flown at speeds up to 225 mph (360 km/h).

The X-49A YSH-60F flight demonstrator will be updated with a lifting wing taken from an Aerostar FJ-100 business jet. A ring tail will also be added and the helicopter drive train will be modified to accommodate VTDP. Piasecki will conduct integrated tests of the modified drive train at the Navy’s helicopter transmission test facility.

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The cockpit controls will be modified with the addition of a manual prop pitch override on the collective for the ring tail. This will be 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 will be integrated into the aircraft’s existing mechanical controls to reduce pilot workload. Weight added to the X-49A YSH-60F will be about 1,600 lb (725 kg). It will have an unrefuelled combat radius of 1,411km following a rolling take-off, and 963km after a vertical take-off, representing a three-fold increase over the standard H-60.

As of 2004 the X-49A YSH-60F/VTDP demonstration program was being transitioned from the U.S. Navy to the U.S. Army.

 

 

The X-49

 

The X-49 is an experimental compound helicopter developed to demonstrate the ability to increase the speed of existing helicopters to 200kt (360km/h).

In October 2000, a demonstration contract was awarded by the US Naval Air Systems Command to Piasecki Aircraft. A Sikorsky YSH-60F was modified as a testbed for the Vectored Thrust Ducted Propeller (VTDP) system.

During 2004 the VTDP program (now X-49A) was transitioned from the US Navy to the US Army's Aviation Applied Technology Division.

The X-49A made its first flight on June 29, 2007.

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