An aircraft with a wing designed to twist in flight is undergoing final checks prior to its maiden flight scheduled for July.
The technology could give future aircraft greater ranges, payloads and efficiency and change aeronautical design.
The Active Aeroelastic Wing is part of a $41m (£30m) research programme involving NASA, the US Air Force and Boeing’s Phantom Works R&D unit.
Conventional aircraft employ moveable surfaces such as flaps and ailerons on the wing and tailplane, but the AAW can be manoeuvred by warping or twisting the wings by up to five degrees.
The key feature is a split leading edge flap, explained Phantom Works AAW programme manager, Dr Jim Guffey. ‘It is broken into inboard and outboard sections. The outer edge is shorter so we can put plenty of force into the wingtip, to provide the twist effect.
‘We removed the aluminium skin and panels from the wing, replacing them with lighter, thinner aluminium or composite material substitutes, and modified the flight control computers,’ he said.
With NASA considering future aircraft that change their shape completely to suit their speed and altitude, Guffey believes that to build these, you must understand the properties of twisting, undulating and warping surfaces.
The test model includes additional actuators, but a production aeroelastic wing would have less reinforcement and so could be thinner, lighter and more aerodynamically efficient.
The team chose a US Navy F/A-18A Hornet for the test, as its original wing designs had shown unwanted twisting and torquing motions. These were eliminated in production, but made the Hornet ideal for the AAW experiment, which aims to prove safety and feasibility.
Over 200 sensors on the wings and fuselage will provide readings when flights start, allowing engineers to monitor loadings via an instant data-link. ‘In itself, this is a major accomplishment,’ said Guffey. The test flights will tell the team whether the aircraft can fly properly under normal conditions and allow them to develop a ‘map’ of aeroelastic loads. This will help them design new ‘control laws’ for when the experiment begins in earnest next year.
Guffey said the idea was really to save weight and structure. He said: ‘The AAW’s principles would work best on long, slender wings, but has applications ranging from military unmanned aerial vehicles to passenger jets.’
It could also lead to radical departures in aeronautical design. ‘Fighter aircraft don’t roll well at high speeds and altitudes,’ said Guffey. ‘There’s less to bite into, therefore the aircraft uses the tail to roll.
‘With the AAW concept, the entire wing would act as a rolling surface, allowing designs that dispense with the tail.’