Efficient testing for Trent 1000 controls

The Trent 1000 project has created a particular reason for developing an integrated test strategy for its electronic control units at Goodrich

The Peak Group has now supplied three production acceptance test rigs and three assembly test rigs to Goodrich, as well as three interface test adapters used with closed loop hardware/software integration systems developed by Goodrich engineers for developing and validating product software.

Goodrich's Hall Green (Birmingham) site produces electronic control units for a range of fixed wing and helicopter aero engines, particularly for Rolls-Royce, which is developing the Trent 1000 engine for the Boeing 787 Dreamliner.

Although the aero engine sector is technically innovative, its products might be in service for more than 30 years, and this has an influence on the approach to testing.

The Rolls-Royce engine has already been selected for 85 aircraft and each of these requires two control units, so for Goodrich, it is a major long-term project involving a considerable amount of testing during the design and certification stages and also in ongoing production acceptance testing.

The company is also involved in projects such as the Trent 500 engine for the Airbus A340, so there is a considerable variation in the test requirements despite production volumes being relatively low compared to some industries.

The Trent 1000 project has created a particular reason for developing an integrated test strategy not only for in-house use, but also as the basis for systems that could be supplied to end users such as airlines and worldwide repair centres.

The engine control units are housed on one side of the engine, and are comprised of backplanes and a number of printed-circuit boards, connected to the engine by high-reliability aerospace connectors.

Goodrich has a full production acceptance test system which includes the signal simulation and measurement resources for full parametric testing, as well as an assembly test rig that carries out basic functional testing with a set of fixed loads to check that the unit has been assembled correctly.

In both cases, a generic test system is interfaced to the different units under test via a number of dedicated fixtures called interface test adapters.

Each test unit consists of a 19in rack containing power supplies (including high-voltage programmable units), communications interfaces, simulation hardware and PXI-based test and measurement instrumentation.

A typical engine control unit has many input/output interfaces, and the test rigs will validate each signal type individually as well as simulating different types of sensor and output.

Inputs examples are position, speed, temperature and pressure; on the output side there might be drive switches, relays, solenoids and motor drives.

Naturally, rigorous tests are carried out - both at unit level and board level because of the high reliability required in the final product and the adverse environment in which the engine control units have to work.

These include temperatures between -55 and +85C and under monitored vibration conditions.

The test system strategy was produced by Goodrich engineers using information supplied by Rolls Royce engineers.

The Peak Group were then asked to act as the integrator for both mechanical and electronic aspects of the test rigs.

A key factor in this decision was the fact that Peak is the exclusive UK agent for the mass interconnect interfaces made by the Virginia Panel Corporation (VPC), which are ideally suited to form the heart of the ITA units.

The Peak Group had previously supplied Goodrich with individual items of test hardware.

Chris Hailes, the engineer responsible for the Goodrich test strategy said: "We are very pleased with the support that the Peak Group engineers have given us on this ongoing project.

"We believe that we now have a system in place that will stand us in good stead for the future and allow us to offer an enhanced service to our customers worldwide".

Emphasis has been placed on ease of use, access and maintenance, and as many standard off-the-shelf products from leading multinational suppliers as possible have been specified.

Extensive commonality between the test rigs helps minimise spares holding and reduces the training of support personnel.

(Updated by CR, May 2007).

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