TYPE: New-concept rotorcraft.
PROGRAMME: Began with US Army contract to develop a compound helicopter incorporating the Piasecki VTDP concept for the AH-64 Apache and AH-1W SuperCobra. Programme objectives were met or exceeded by both the AH-64 VTCAD (Vectored Thrust Combat Agility Demonstrator) and AH-1W VTCAD configurations, resulting in increased maximum level flight speed; 50% improvement in longitudinal acceleration and deceleration capability in level flight; 50% decrease in turn and pull-up radius at speeds in excess of 176km/h and handling qualities at least as good as those of the baseline AH-64A and AH-1W. In addition, tactical simulations confirmed superiorly of the VTCADs over the standard Apache and AH 1W SuperCobra.
A separate US Navy contract, awarded in 1995 and valued at US$16.1 million, involved investigation into application of VTDP technology to the AH-1W(4BW)/AH-1Z four-blade rotor configuration. The Navy contract, recently completed, included ground testing of the full-scale VTDP and additional flight controls simulation and testing of the 4BW/ATDP configuration.
Piasecki then proposed flight demonstration of this technology to the Navy on an AH-1W(4BW), but instead was awarded a four-year US$26.1 million contract on 28 September 2000 for integration, testing and flight demonstration of VTDP on a modified Sikorsky YSH-60F. This flight test programme, to begin in 2004, will be conducted by Piasecki. The VTDP concept is being investigated by the DoD as an affordable means of upgrading the capabilities extending the service life of existing single main rotor helicopters such as the UH-1, UH/SH-60 and AH-64 until the follow-on Joint Replacement Aircraft is fielded some time after 2030. Most recently, the US Air Force selected the H-60/VTDP concept as one of a number of alternatives being considered as an upgrade or replacement, to be fielded as early as 2007, for its ageing HH-60G combat search and rescue helicopters.
By mid-2000, Piasecki had constructed and completed ground testing of a full-scale 2.44m diameter Model of H-60/VTDP compound helicopter duct and integrated five-blade ducted propeller. In addition to installation of this unit, modifications to the YSH-60F will include addition of lifting wings (from an Aerostar business twin) and integration of VTDP controls into the helicopter's existing mechanical control system, all of which is expected to add some 726kg to the demonstrator's empty weight. The increase in empty weight will be lower in production versions, which will employ a supplementary power unit (SPU) that will provide an increase in hover payload to offset the increased empty weight.
DESIGN FEATURES: The VTDP comprises a ducted propeller with integral vanes and spherical sectors to vector propeller thrust. It provides lateral thrust for anti-torque and lateral control, in lieu of a tail rotor, as well as forward thrust for auxiliary propulsion. Combined with the lifting wing, it provides for increasing speed to more than 370km/h; greater manoeuvrability; reduced vibration and fatigue loads; and consequent improvement in component lives and reduction in maintenance requirements and life cycle costs.
Piasecki estimated that a VTDP-based H-60 compound helicopter would 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.
Jane's All the World's Aircraft, 2004-2005