Keeping aircraft in the sky: Combustor burn-through testing

In aircraft jet engines, combustors produce hot gas at up to 40 bar and 1650°C or more.

Although unlikely, hot gases could burn through the combustor body, damaging the engine mounting or airframe. In that event, emergency systems quickly shut down the engine, but critical components must survive until that has happened. Aircraft manufacturers show that their protection works by testing under burn-through conditions.

How did HSE help?

HSE's Science and Research Centre has done this testing in the past, but when Mitsubishi Aircraft Corporation (MITAC) approached us, our facility had been unused for several years. Having looked around the world without finding a suitable alternative, MITAC asked us to recommission our test rig.

Our rig burns jet fuel with compressed air in a modified jet engine 'can combustor'. A nozzle funnels the hot, high-pressure gases into a 25 mm diameter, supersonic 'torch' directed at the test sample.

Recommissioning involved refurbishment, replacement or recertification of almost every component.

We carried out two tests, one observed by JCAB, the Japanese aviation authority. Each test lasted three minutes. The test sample, a flat plate, was instrumented for pressure and temperature with both point measurements and thermal imaging.

What were the benefits?

HSE provided Mitsubishi with data that they could then use in their safety assessment and future design work.

By working together with them to optimise the test specification and the test requirements, the necessary information was gained from a minimal test programme.

This was a small but vitally important step in the complex procedure for approval of a new aircraft design.

HSE, (2021). Sixth Annual Science Review, pp.73-74.