Proposal includes catamaran hull linked to large wings that act as sails when folded
The US Naval Research Laboratory is testing scale models of a proposed "Sail-a-Plane" unmanned air-sea vehicle that could be used as the basis for a self-deploying, very-long-endurance sensor system.
The proposed UAV would feature a catamaran hull linked to two large wings that would fold from the horizontal to the vertical plane to act as twin rigid sails when the craft is on the ocean surface. A rear-mounted propeller would provide thrust for flight, with the craft using hydrofoils as landing gear.
A non-flying scale model of the Sail-a-Plane catamaran in sailboat configuration – designated Sail-a-Plane B or Boat – has been tank tested by NRL in the past two months and this month was sailed in a marina in low wind conditions. The catamaran design follows consideration of a monohull design that could land once, but would not be able to return to flight.
A scale model of Sail-a-Plane A – Airplane – is under construction. Composite test results from the two models will be used to support development of the 22.7kg (50lb) Sail-a-Plane C – Converting – possibly this year.
The Sail-a-Plane B model has a 76.2cm (30in) combined hull and fuselage and weighs roughly 1.4kg. The Sail-a-Plane A will have a 145cm wingspan, but will use wheels rather than hydrofoils to allow for ground-based take-off and landing.
Unveiling the concept at Bristol University's UAV Systems conference last week, James Kellog, an NRL research engineer, said studies indicate the electrically powered design is scalable up to platforms weighing 680kg with a 10m wingspan. However, larger craft could be possible using combustion rather than electric engines.
Kellog said the concept has emerged from the ongoing survivable autonomous mobile platform-long endurance (Sample) project aimed at developing better air vehicles and surface craft for electronic intelligence gathering missions. "This is a 21st century version of the old Russian trawler that used to follow everyone around [during the cold war]," he said.
PETER LA FRANCHI/BRISTOL
Source: Flight International
