A team of engineers at aircraft manufacturer Bombardier Aerospace in Belfast could be set to share a £50,000 design prize later this year.
The group is one of the finalists for this year’s coveted MacRobert award – a kind of ‘Nobel Prize’ for engineering design.
Bombardier has made it onto a shortlist of just three companies, in recognition of its developments in the field of reverse thrust for aircraft engines, coming up with a more efficient design that not only stops a plane faster, but also makes for quicker maintenance.
‘It is simpler than the old design and will improve reliability and maintainability,’ said Bombardier’s principal powerplant specialist Mike Hatrick. ‘It also delivers 10% more stopping force, so the engines can run slower but give the same braking power. This reduces both environmental noise and wear and tear on the engine.’
Thrust reversers are particularly useful on wet runways, when the wheel brakes are not efficient enough to slow the plane down as it lands, as well as during aborted take-offs when very little runway is left in which to stop. The team originally began design work on the new thrust reverser in 1994 for the company’s CRJ-700 regional jet.
While thrust reverser designs differ according to the kind of aircraft and engine involved, they all basically work by using components within the nacelle (the cowling wrapped around the engine) to reverse the powerful air flow within the engine.
Most thrust reversers use ‘blocker doors’ – components within the nacelle that act as hinged doors that move to block – and so ‘bounce back’ – the air flow.
The Bombardier team wanted to simplify this mechanism, as well as improving maintenance access to the engine. Their new design uses part of the nacelle itself to act as a blocker door and reverse the thrust.
To achieve this, the team had to redesign the nacelle fan duct. The duct generates 80-90% of the thrust as it pressurises the exhaust from the combustion process.
Normally this duct is a straight tube shape which requires the hinged doors to close it off. But the new design is an ‘S’ shape. This configuration enables a piece of nacelle to descend, blocking off the duct and redirecting the airflow.
Hatrick’s team believes that fewer components mean a more reliable operation with lower maintenance requirements. Importantly, they had to take care that maintenance access would not be made more awkward (and would preferably be made easier), as incorporated in their new design.
With conventional nacelles it could take over 24 hours to change an engine. In the new design, it takes less than eight hours, using a mounting arrangement that automatically lines up the nacelle’s cowls when they are closed. This saves hours of adjustment by trial-and-error. The cowlings are also counterweighted so that one person can open them easily.
Work on the new design has seen the Bombardier team, normally based in Belfast, ‘go international’, spending several months thrashing out the details with colleagues at other Bombardier design centres including the company’s HQ in Montreal and its offices in Boston and Cincinnati.
Bombardier Aerospace in Northern Ireland is one of three finalists for this year’s MacRobert Award, which is organised by the Royal Academy of Engineering. The other two are Middlesex-based Sensaura for 3D audio, and Brighton-based Southern Water for a novel separator for sewage treatment. The winner of the award will be announced in November.