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African glider aims to take on the world, but international recognition remains a challenge

UYS JONKER A glider’s performance depends mainly on the aerodynamic design, which, for the JS-1 glider, took five years to perfect

JS-1 GLIDERA glider needs to be able to climb well using updrafts and it must have good cruising performance

24th July 2015

By: Anine Kilian

Contributing Editor Online

  

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In the unlikely location of Potchefstroom, in South Africa’s North West province, high-quality glider aircraft are being manufactured to an indigenous design that is said to be competitive with the best in the world.

The JS-1 glider, manufactured by Jonker Sailplanes, is the only type-certified aircraft designed and manufactured in Africa, with type certification being a requirement for an aircraft to be manufactured and sold commercially.

Jonker Sailplanes cofounder Uys Jonker tells Engineering News that obtaining type certification for the glider has involved a rigorous process to verify and approve not only the design but also the manufacturing processes.

Various airframe parts had to be produced specifically for testing to destruction in structural test rigs that had to be observed and verified by a Civil Aviation Authority (CAA) team.

When the JS-1 underwent flight-test trials, it was accompanied by a chase plane, which filmed the glider as it flew and manoeuvred.

A CAA design engineer flew in the chase plane to verify that all the required procedures were followed. Near the end of the programme, the CAA brought in a highly experienced Class 1 test pilot and flight-test engineers from Denel, as well as veterans of the Cheetah and Gripen programmes, to fly the JS-1 and verify all the flight data accumulated by Jonker Sailplanes earlier in the flight-test programme.

“Being the only type-certified aircraft in the country causes challenges for us and the CAA. Legislation exists that enables South Africa to manufacture aviation products, but we are the first company to test these regulations and have had to face all the obstacles of testing,” Jonker states.

International Recognition

He says the current main challenge is getting the JS-1 type certification recognised internationally. “Before certification is achieved, we can sell this aircraft only to countries where experimental certification is allowed,” he says, describing it as a complicated process that places a lot of pressure on the company to complete certification timeously, which takes three years.

Unfortunately, he explains, South Africa has no history in producing type-certified aircraft, and the European Union (EU) protects its market by disallowing type certificates of nonmember States.

“Because we are not a member State, there is no financial benefit for the EU to approve type certificates from other countries because they could lose sales,” he says.

He adds that the EU does not make it easy for the Department of International Relations and Cooperation (Dirco) to negotiate on equal terms, and there is no bilateral agreement in place to enable South Africa to export its aviation products to the EU.

“The EU has proposed an unfair and biased bilateral agreement to South Africa, which Dirco is uncomfortable to sign because of the existing proposals; therefore, the EU instructs the European Aviation Safety Authority not to accept our certification,” he says.

Jonker explains that progress made in the past five years has been very slow and that local aerospace companies are forced to partner with a European partner if they want to export to the EU.

Integrated Design

Nevertheless, demand for the glider remains robust, which Jonker attributes to the aircraft’s unique design principles. “We have followed an integrated design approach and have incorporated aspects such as aerodynamics, structures and pilot comfort in the design plan,” he says.

He explains that a glider’s performance depends mainly on the aerodynamic design, which, for the JS-1 glider, took five years to perfect.

Jonker notes that his development team used modern computer design programs that simulate airflow instead of relying solely on wind tunnels, which is what most glider manufacturers do.

“We designed the basic air foil using two-dimensional flow-prediction simulation software to develop a superior laminar profile suitable for a high-performance glider. We constructed a wind model of the profile and tested it in a wind tunnel, which confirmed that the results from the wind tunnel were the same as those that we calculated using the software.”

He notes that the team then started with an iteration design approach, made a small modification to the profile and ran the simulation software again.

“It took 24 hours for the first simulation to complete its run. This helped us to steer the profile in a specific direction. The first profile’s name was A1; when we reached T12, we found that we could not make any improvements,” he says.

Jonker notes that a glider needs to be able to climb well using updrafts and must have good cruising performance.

“Gliders have negative flaps – ours are made for climbing and cruising. We also designed winglets to control the airflow around the wind tips to save on drag.”

The company also spent a lot of time designing the fuselage because, Jonker says, there is a lot of interference drag between the fuselage and the wing, which is an area where lift is lost and drag can increase significantly.

Since completing the design and manufacturing of the aircraft, a number of design changes have been made.

“The first change was to make it a multiclass aircraft by extending the wings to 21 m and increasing the weight from 600 kg to 720 kg,” he says.

The second improvement, notes Jonker, was installing a retractable jet turbine engine. The glider can cruise with jet power up to speeds of 220 km/h.

The design of the JS1-C with 21m wingspan started in October 2013, with the outboard wing having been redesigned using the latest Computational Fluid Dynamics design methods.

Jonker Sailplanes also upgraded its 18-m-span configuration, named the JS1C-18 EVO.

“The JS1C-18 EVO redefines handling in the 18 m class, offering an improved roll rate and superb control at slow speeds. “The increased wing loading, combined with new tip aerofoils and third-generation winglets, also gives it the edge at high speeds,” he explains.

He adds that the glider offers the serious competition pilot a performance advantage while remaining suitable for every pilot, owing to its handling qualities.
“We also integrated bug wipers so that pilots can clean the leaning edges of their wings, which is required for laminar airflow over the wings. “Anything that gets stuck on the wings, no matter how small, will reduce the performance of the aircraft,” he says.

Jonker, who outlined the company’s journey at the recent Manufacturing Indaba, says the event was helpful in enabling the industry to voice its concerns and highlight the obstacles preventing improvement and expansion.

He says manufacturing creates wealth and it is, thus, crucially important for South Africa to reindustrialise. “Government fully understands that and has incentives in place to try an integrated approach so that companies can actually work together towards the common goal, which is to create jobs and wealth for South Africa,” he concludes.

Edited by Martin Zhuwakinyu
Creamer Media Senior Deputy Editor

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