DARA (Defence Aviation Repair Agency in the UK) has completed a state-of-the-art Aircraft Servicing Facility at St Athan in South Wales. DARA awarded the hydraulic system contract to T.A. Savery, based in Birmingham, UK. T.A. Savery under the direction of R. Peacock, systems director, designed, manufactured and installed the complete hydraulic system.
At the heart of the facility are the hydraulic ring main systems that allow the aircraft hydraulic systems to be fully functionally tested, filled, drained and flushed. The ring mains and associated equipment are primarily designed to operate the hydraulic systems incorporated into fast jets that use either self-pressurising reservoirs (Tornado, Eurofighter and Jaguar) or pressurised reservoirs (Harrier and Hawk).
The design incorporates the following philosophies:
* Supplying a system that meets the aircraft test requirements including the tight tolerance bands on supply and return pressures, flow rates and hydraulic system cleanliness.
* Supplying a system to automatically meet the dynamic response required to test the aircraft, which has randomly varying loads.
* Supplying a system requiring minimum operator input.
* Minimising the operating and maintenance costs.
* Maximising the system availability and mean time between failure periods.
The two hydraulic powerpacks that are housed in the purpose built plant rooms, have a total installed power of 1,575 MW and are able to supply a total flow of 2520 litres/min at 31,5 MPa. This is fed through 100 mm diameter pipework into the two hangars with over 3,5 km of pipework involved in the installation.
These mains feed fluid to 16 aircraft interface units. The aircraft that are located in the two hangars have their hydraulic systems connected to the testing system by flexible hoses. The hydraulic fluid in the ring main and power packs are maintained at high cleanliness levels by use of highly efficient filtration as supplied and manufactured by M.P. Filtri.
The electronic/computer system controls the interface parameters with the aircraft and minimises the human input requirements by:
* The use of a touchscreen console adjacent to each aircraft interface unit that allows programmable pre-set levels to be loaded for various types of aircraft and types of test.
* Matching the flow rates from the Powerpacks automatically via an algorithm to match the actual requirements of the aircraft. This greatly reduces and minimises the operating costs as well as maximising the reliability.
* The inclusion of a PC-based scada system is to provide realtime monitoring of the ring main systems with historical data being gathered and stored on the flows, pressures, temperatures, cleanliness, operating times and sequences, etc, to assist with monitoring and fault finding. This data can be displayed and printed in graphical or tabular format.
System contamination monitoring is achieved by using an in-line particle counter (PML2) manufactured by M.P. Filtri. Incorporating the particle counters into the hydraulic system was achieved by using a software package called 'Modbus'. This protocol enables the PML2 to be programmed to communicate with a programmable logic controller (PLC). This measures and reports the cleanliness of the various aircraft hydraulic systems. The technicians are able to view the cleanliness of the hydraulic fluid during all periods of servicing and testing, once the technician has finished the servicing, the aircraft's hydraulic systems can be checked to ensure that the correct operating cleanliness is achieved. Achieving and monitoring the correct cleanliness standards for the reliability of today's aircraft is critical. M.P. Filtri is represented by Hydrasales in South Africa.
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