Airworthiness testing of new light aircraft is returning to the UK, thanks to a pioneering partnership involving a championship-winning aerobatic pilot and aircraft builder, and the University of Sheffield Advanced Manufacturing Research Centre with Boeing (AMRC).
Lincolnshire-based Game Composites was founded with the aim of creating an easy handling two seater aircraft that would be recognised as the most fun to fly aircraft in the world. It says the GB1 prototype weighs only 575 kg can cruise at more than 200 knots and has a range of 1,000 Nautical Miles on 320 litres of fuel or can carry 95 litres for aerobatics.
Although the GB1 has been designed and built in the UK, Game’s initial plan for fatigue testing involved shipping the aircraft to the Czech Republic for full airworthiness certification, until Phil Spiers, Head of the AMRC’s Advanced Structural Testing Centre (ASTC) became aware of the project.
“When I heard about the plans to design and build an aerobatics aircraft within 60 miles of the AMRC, I was determined that we should keep the whole production process, including testing, inside Britain,” says Phil.
The ASTC believes this will be the first time in more than 30 years that a plane has been designed, built and tested in the UK.
“We hadn’t done it before but we have the skills and experience in abundance to help this manufacturer get its planes into the sky as quickly as possible,” adds Phil.
Engineers at the ASTC designed a bespoke test rig to apply forces up to 10 times those exerted by gravity, simulating the forces the aircraft will have to cope with as it carries out high speed manoeuvres. ASTC made some of the parts of the rig, while other components were made elsewhere within the University of Sheffield Advanced Manufacturing Research Centre (AMRC) with Boeing.
The ASTC called on the skills of welding specialists from the Nuclear AMRC and the abilities of the AMRC’s own apprentices to construct a complete “whiffletree,” which distributes test forces over the aircraft’s fuselage and wings, causing them to twist and flex as they are designed to do in flight.
Mounting the plane on the whiffletree was a big challenge in itself. The fuselage, with wings fitted, had to be lifted four metres into the air and then flipped upside down. “It was the first ever barrel roll inside the ASTC!” says Phil.
Engineers had to position mounting points on the ASTC’s 10 metre square ‘Strong Floor’ to within 1 millimetre, manufacture complicated loading brackets to similar accuracy and attach strain gauges precisely at 17 locations on the plane’s surface.
“It was important for us to get things as close to the customer’s drawings as possible as they have calculated the loads and made their designs according to how they will be distributed within the aircraft’s structure,” says Phil. “If we were a few millimetres out, it would make a big difference to where the loads go, which is why we have had to create quite a complicated load fixture.”
The challenges didn’t end there. The ASTC also had to devise a way of heating the whole of the aircraft to 70°C while some of the tests were carried out.
Insulating the rig required the help of SIG Technical Insulation and MacGregor & Moir, subsidiaries of Sheffield-based leading European supplier of specialist building products SIG.
SIG’s technical specialists suggested using an in-house laminate insulation board, more normally used to prevent heat escaping from metal ducts that are at the heart of heating and ventilation systems in commercial buildings.
“We always try to use local suppliers, wherever possible and SIG’s response more than justified our choice,” says Phil. “The laminate insulation board was the perfect solution and the level of service SIG provided was among the best I have ever seen.”
Centre staff used the panels to create a box around the aircraft’s body which maintained the temperature, while remaining cool to the touch outside.
Around a third of the testing has been completed and the aircraft’s structure is performing so well that the programme could be extended to increase the plane’s approved in service lifespan.
Phil and his colleagues believe that the successful completion of airworthiness tests at the ASTC will open the way for the testing of light aircraft to return to the UK and further contracts.