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Bosch Rexroth helps to give Airbus wings!
Article Type: Aerospace technology From: Aircraft Engineering and Aerospace Technology: An International Journal, Volume 80, Issue 3.
Hydraulic platform lifting systems designed and supplied by Bosch Rexroth are playing a key role in the manufacture of wings for the new Airbus A400M multi-role military transport aircraft (Figure 11).
At 45m long, and with a span of 42m, this versatile and innovative aircraft is by any standards an impressively large machine. Its 23m long by 4m wide wing boxes, each of which weighs 3 tonnes are, in fact, believed to be the largest carbon fibre reinforced plastic composite wings ever made.
Figure 11 The Airbus A400M multi-role military transport aircraft
For jigs to simplify the manufacture of these enormous wings, the Airbus Wing Manufacturing Facility based at Filton near Bristol turned to Electroimpact of Seattle, USA, the company that had previously supplied the jigs used in the production of wings for the Airbus A380, the world's largest passenger aircraft.
After an extensive tendering process that included a thorough technical evaluation of the solutions proposed in the competing bids, Electroimpact awarded Bosch Rexroth a contract for the complete hydraulic systems to operate the total of 16 hydraulic platforms needed for two wing jigs. Bosch Rexroth was also awarded an additional contract by Electroimpact to supply hydraulic systems for use with ancillary equipment on the two jigs.
Following the successful completion of the first two jigs, Electroimpact has now placed an order for a third wing manufacturing jig.
The wing jigs incorporate two elevating platforms on each side of the wing, one platform having a lift of 3.5m, the other with a lift of 2.5m. An essential requirement is that the motion of the cylinders used to lift the platforms should be accurately synchronised, so that the platforms remain absolutely level under all conditions.
A key factor in the success of Bosch Rexroth's tender was that it was able to demonstrate this synchronisation on a simulated assembly. In fact, synchronisation better than ^2mm over the whole of the longer 3.5m stroke was achieved, compared with the specified requirement of ^5mm.
Bosch Rexroth was also able to show that it could produce cylinder and valve block assemblies that were compatible with Electroimpact's existing design for receivers the chambers sunk into the concrete floor below the elevating platforms to accommodate the lifting assemblies, so that the platforms can be lowered to floor level.
Further factors which aided the success of the Bosch Rexroth offer were a power unit design that allows up to three rigs to be operated from a single power pack, and the company's proven capability in the areas of design, site installation and project management.
In the final system, the platforms, that have a worst-case total load of 13 tonnes are each driven by two cylinders. The cylinders used are customised versions of Rexroth CDL products.
Additional guidance and support for the lifting system is provided by linear slides and the cylinders are fitted with linear transducers to provide the accurate positional feedback needed for the control system to maintain synchronism.
All of the cylinders are fitted with safety manifold blocks to prevent the platforms descending unexpectedly should the hydraulic system be damaged or develop a fault.
The cylinders have a maximum working pressure of 210 bar, and are fitted with seals to suit the Castrol Anvol SWX FM hydraulic fluid that was chosen for the project because of its fire-resistant properties. To protect the lifting mechanism from the abrasive effects of the carbon fibre dust and swarf produced during the manufacture of the wings, the lifting assemblies are fitted with flexible gaiters.
Power for the lifting systems is provided by a 2,000l hydraulic power unit which incorporates two 55kW electrically driven pumps, each delivering 220l/m at 135 bar. The pumps are arranged in a duty/standby configuration, so that normal operation can be maintained even if one of the pumps is out of service. To save valuable space in the assembly area, the power unit is mounted within a GRP enclosure and is installed outdoors.
To maximise energy efficiency, the pumps are fitted with pressure control arranged so that they deliver only the pressure and flow necessary to satisfy the current demand on the system. This energy-saving feature is another factor that helped to set the Bosch Rexroth design apart from the other proposals, as these had pumps which would have run continuously at full output, even when the jigs were not in use.
The control system for the elevating platforms is built around Rexroth HNC100 digital axis controllers used in a closed-loop configuration and arranged to provide the accurate synchronisation needed between the two cylinders used on each platform. The control system also incorporates a pressure/force controller to detect overloading of the platforms, and a cable-break monitoring safety feature for the linear position transducers.
Hydraulic equipment supplied by Bosch Rexroth for ancillary functions on this project includes valves and cylinders to operate the lower leg deployment, boom lift, boom extend and end gate systems. As in the case of the systems for the main platforms, extensive use is made of dual redundancy in the ancillary systems to ensure that the risk of downtime is minimised.
To further help in keeping downtime to a minimum, Bosch Rexroth has given careful attention to making the installation easy to maintain. In particular, great care has been taken to ensure that equipment installed below floor can be easily serviced. Numerous isolation points are, for example, provided so that, in the event of a fault, individual sections can be quickly isolated as an aid to maintenance.
The Airbus A400 military transport is a new breed of aircraft, the design of which takes full advantage of the latest developments in aviation and materials technologies. Manufacturing such a genuinely groundbreaking product presents many challenges, but those associated with the production of the wings have now been effectively addressed, with a little help from hydraulic systems developed and supplied by Bosch Rexroth.
For further information, please contact: Bosch Rexroth, Tel.: +44 (0) 1480 223200, Fax: +44 (0) 1480 470789, E-mail: email@example.com