Military and civil cargo transport roles planned for tail-sitting, winged, VTOL UAV

Tethered hover tests of the SkyTote vertical take-off and landing (VTOL) unmanned air vehicle are expected to start at Mojave, California, in September, pending the completion of static tests now taking place.

The US Air Force Research Laboratory (AFRL) vehicle is being developed by AeroVironment under a four-year small business initiative research programme. The tail-sitting, winged UAV is designed to provide a simple, reliable and low-cost cargo transport method for military users initially, although civil versions are planned in the longer term. Potential operators include the US Special Forces Command, says AFRL.

The UAV takes off, hovers and lands like a helicopter using a pair of counter-rotating prop-rotors powered by a 38kW (52hp) UEL AR801 Wankel engine. After take-off, the UAV is designed to transition to wing-borne flight supported by a 2.4m (8ft) span wing and a 2.3m span cruciform tail, which doubles as landing legs.

The concept demonstrator is expected to develop into a family of scalable SkyTotes ranging from backpack versions with a 4.5kg (10lb) payload, to larger variants capable of carrying more than 180kg. The demonstrator, which has a 23kg payload, will be tested initially in a whirl pit at Mojave. The SkyTote will then be tested at the US Army's Yuma Proving Grounds in Arizona, where it will demonstrate free-air hovering, transitional flight and recovery.

"The transition to aircraft mode should be fairly simple, but the interesting part will be the transition to helicopter mode," says AFRL Air Vehicles Directorate team leader Thomas Cord.

Several horizontal to VTOL transition manoeuvres are being considered, including a simple pop-up involving a fly-up, power back and hold with power, a 1g stall followed by a full-power recovery, or a knife-edge sideslip transition from horizontal to vertical flight. "That should be the best to automate," says Cord. Testing is due to end in December.

Source: Flight International