08 Mar 2007
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Engine health diagnostics using radar
Catastrophic engine failure in jet aircraft can be prevented using a new form of radar. The radar keeps constant watch over the engine intake and automatically warns if foreign objects have been sucked in, creating havoc. The same technology can be used to ‘listen’ for subtle changes in the engine’s vibrations and give early warning of trouble.
Maintenance engineers can then take action to repair any damage before it reaches dangerous levels.
The ATC has developed a unique system called Engine Health Diagnosis Using Radar (EHDUR) which can monitor the condition of the jet engine’s air intake and compressor fans. It is able to tell the difference between damaging and non-damaging objects which enter the engine accidentally. “The front stages of a jet engine are highly strung. If something is accidentally ingested it may cause damage to the fan blades which may not be visible by inspection” said David Shephard, project manager at the ATC. “Presently, this type of damage can only be picked up by visual inspection by ground maintenance crews”. he says.
The system can give an automatic warning if ‘Foreign Object Damage’ (FOD) to a fan blade is imminent. This speed of warning can be vital as minor damage can rapidly grow in the fast moving environment of a jet engine. “A blade can fall off an engine within minutes of a fault occurring. Cracks can develop quite rapidly following damage especially as performance of jet engines becomes higher and higher” says David.
The breakthrough in radar technology needed to create EHDUR is the use of miniature antennas which are fitted into existing engine inspection ports or the engine’s air intake. These antennas are designed not to interfere significantly with the airflow into the jet. As well as monitoring FOD, the system is also capable of giving the engine a constant ‘health check’. The radar can be used to monitor mechanical vibration of the moving parts at the compressor stage and then sense if any changes to the normal patterns have occurred. By detecting changes to the vibration, early diagnosis of specific faults should be possible. An engine’s operating characteristics change over time as a result of FOD, vibration and general wear and EHDUR could provide the ability to measure and analyse this wear.
This capability is of increasing importance since new aircraft designs are required to include integrated ‘vehicle health management’ technology that monitors not just engines but also on-board systems and structures. EHDUR is currently being evaluated with the help of Rolls-Royce and the UK MoD and successful blind trials have been performed in ground test facilities using the Harrier’s famous Pegasus engine. The technology is not restricted to any particular type of jet engine so there are excellent prospects for EHDUR as a standardised system for any jet engine.
“We hope to get this flown soon using the Advanced Technology Demonstrator Centre at BAE Systems Warton site in the UK. If successful, the system could be equally useful for both military and civil jet engines and could be in service during the next five years.” says David.
