Application Briefs

The Air Force has announced that the MLB V-Bat Vertical Take-Off and Landing (VTOL) UAV from the MLB Company (Sunnyvale, CA) has been selected for a Phase II SBIR award. The military branch seeks a vehicle that has an 8-ft wingspan, 10-hour endurance, 55-lb gross take-off weight, and 70-mph cruise speed. The V-Bat’s combination of VTOL operational convenience with the safety of a shrouded fan and fixed-wing duration in a small UAV system will enable local situational awareness for UAV operations in confined areas. Last year, under a DARPA contract, MLB demonstrated precise emplacement of small payloads from the V-Bat, operating in hover mode under a vision-based control system.

The MLB V-Bat in flight.
With the Phase II SBIR award, MLB will build vehicles and conduct a comprehensive flight test program for the V-Bat through all phases, culminating in fully autonomous operational demonstrations. Brigham Young University will develop control algorithms and support flight tests. AAI Unmanned Aircraft Systems (Hunt Valley, MD) will prepare the system design for low-rate initial production and refine requirements through customer engagement.

A strong mission pull exists for Tier-II sized long endurance VTOL vehicles. The V-Bat design was originally solicited by a commercial customer for aerial mapping. MLB Company has been approached by potential customers in several government agencies and by commercial groups seeking an anti-piracy solution.

The V-Bat incorporates a ducted fan lift system instead of conventional tail surfaces on a streamlined airframe, enabling vertical take-off, landing, and aerodynamic efficiency at high cruise speeds. The design concept merges the platform of sailplane-like wings and slender fuselage with the mechanically simple, ducted-fan lift system that provides control and lift for vertical flight, while simultaneously replacing the aircraft’s tail surfaces. The configuration, specifically the dual-use of the ductedfan lift system as the empennage of the aircraft, represents a minimal deviation from proven fixed-wing aircraft designs.

A key problem with many previous tail-sitter designs has been the high probability of tip-over at touchdown, which may damage the aircraft especially if it uses exposed rotor blades. The prototypes have demonstrated the ability to tip-over on landing and not sustain damage. A shock absorbing noseskid system keeps the loads from tipping over, and the duct shields the rotor and vanes from any damage when contacting the ground.

The system has been extensively field tested. A typical rotorcraft achieves an effective lift-to-drag (L/D) ratio of 6:1 in level flight. The V-Bat has a ratio of nearly 15:1 L/D.

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