Denel Saab Aerostructures on cusp of Airbus success

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Denel Saab Aerostructures (DSA), the 80:20 joint venture between SA’s state arsenal and the Swedish defence giant, is in negotiations to finalise a contract to produce the A, B, C and D ribs of the Airbus Military A400M Loadmaster tactical airlifter.
DSA recently machined an example of Rib D to Airbus specifications and the company hopes to capitalise to this to capture a production contract.
The Loadmaster is currently in prototype phase, with the first aircraft rolled out in June. It still has to make its first flight. The wikipedia notes that some 180 aircraft are order, which means a significant multiyear income flow for DSA, should it be successful.
        
Executive manager business development Grant Sampson says winning the bid “would be of great benefit to the industry.
“We have all the machinery, we`re just waiting for the contract,” he adds, saying this included the acquisition of a high-speed five-axis Zimmermann CNC machine as part of a “tremendous facility upgrade” that reportedly cost the state R660 million.          
DSA is part of the Loadmaster programme as a result of SA`s planned acquisition of eight of the airlifters. “DSA had the opportunity to develop and manufacture selected work packages on the A400M, the largest being the wing-fuselage fairing,” says Sampson.
“Arguably one of the most complex components manufactured by DSA is … centre wing box (CWB) … Rib D. The CWB is perhaps one of the most critical structural components on the A400M and connects the wing onto the fuselage and endures immense forces during flight.
The CWB comprises eight ribs spaced about 420mm apart. The middle two are Ribs A with the outer ribs being D.
Rib D is “one of the most highly loaded components on the entire A400M as it supports the fuselage attachment lugs. These lugs support the weight of the aircraft during flight.
Sampson says the rib is a complete machining with integral stiffeners. Any loading is transferred to the rib via shear into the solid web. The stiffeners prevent the solid web from buckling and carry the load out through the rib caps. The rib has cutaways for the passage of control rods and fuel as well as hydraulic lines.
The executive adds that Rib D is machined from a solid 3000kg aluminium billet. “A special vacuum fixture supports the billet during the machining process.”
The milling machine starts the process by finding the billet`s edges and calibrating itself. “The spindle speed on the Zimmermann is an impressive 40 000rpm,” Sampson adds.
Rough machining whittles down the billet one side at a time and after some hours it begins to take on the shape of the final rib. Once all excess material is removed, fine machining takes place. Sampson says the final rib weighs 100kg and takes about 80 hours to manufacture.