Silent Aircraft

The Silent Aircraft Initiative (SAI) The Cambridge-MIT Institute's 'Silent' Aircraft Initiative was launched in November 2003 with a bold aim: to discover ways to reduce aircraft noise dramatically, to the point where it would be virtually unnoticeable to people outside the airport perimeter.

The initiative aims to improve competitiveness in the UK aerospace sector by changing the way research is undertaken, through extensive collaboration with a wide franchise of stakeholders . By embracing this larger community, the Silent Aircraft Initiative seeks to produce a truly optimised concept design that contributes to the prosperity of the UK in an environmentally sustainable way.

6 November 2006: Public Presentation of the Silent Aircraft Research Join us (very quietly) for the unveiling of the Silent Aircraft Initiative’s conceptual design of an ultra-low noise fuel efficient aircraft, and a discussion of the challenges ahead. This event, marking the end of this stage of the Silent Aircraft Initiative, will bring together a wide community of interested parties including pioneering academics, regulators, airport operators, airlines, aerospace manufactures, policy makers and representatives of community groups. The event will include the first public presentation of the Initiative’s conceptual design, feedback on the design from Boeing and Rolls-Royce, and a discussion of the challenges to be overcome if such an aircraft is to be realised within the 2030 time frame. For more information and to register to attend the event, please see the event item on this website.

An Extensive Network of Partners The initiative is bringing together leading academics from Cambridge University and the Massachusetts Institute of Technology (MIT) with an extended 'Knowledge Integration Community' (KIC) of representatives from all parts of the civil aerospace/ aviation industry. Members of the 'Silent' Aircraft Community are working together, sharing knowledge and developing the design for an aircraft that has noise reduction as its primary consideration. Partners include: • • • • • •

BAA Boeing Bruel & Kjaer (B&K) Civil Aviation Authority (CAA) DHL easyJet

• • • • • • • • • • • • •

ecotec HACAN ITP Lochard Lufthansa Cargo Luton Airport Marshall Aerospace Met Office National Air Traffic Services (NATS) Nottingham East Midlands Airport (NEMA) Rolls-Royce plc United Parcel Service (UPS) Wyle Labs

These partners have provided access to industry software tools, and have been involved in reviews of the emerging designs. In addition to the KIC, other research collaborators include Georgia Institute of Technology, KTH Sweden, ISVR, Messier Dowty, NASA and NLR.

Integrated Research The research is focused around the development of a conceptual design of a new aircraft which is no louder than the background noise outside a typical urban airport perimeter. The aircraft should have competitive fuel burn and the design must be credible in terms of in-depth reviews by industry. One of the designs being considered in the ‘Silent’ Aircraft Initiative is illustrated left. In addition, the team the team is working with an airport, air traffic control and local airlines to certify and flight test new enhanced approach procedures with current aircraft types. The approaches are an enhanced form of Continuous Descent Approaches (CDAs) in which the aircraft is at flight idle, and hence quieter, throughout the approach to land.

Reducing noise at take-off The engines are the largest sources of noise from aircraft at take-off and therefore to meet the Silent Aircraft noise target a novel engine design is required. A team of researchers from Cambridge University is working with engineers at Rolls-Royce in Derby to produce a completely new engine design. This needs to balance the reduced jet speed required for noise reduction against the level of thrust required for take-off. The team has found that the total exhaust area must be about twice that of today’s conventional jet engines in order to achieve this balance.

Ensuring good cruise performance The designs use a highly efficient airframe designed at MIT which has a high ratio of lift to drag forces. This reduces the cruise fuel burn. Larger engines could increase the drag

experienced during cruise, which would counteract the benefits on fuel consumption of the efficient airframe. The designs reduce the amount of drag contributed by the engines by changing the way they are mounted on the airframe. Instead of hanging them below the wing, they are embedded within the aircraft. By locating the engine intakes on the upper surface it is possible to shield people on the ground from the engine noise.

Reducing noise at landing It is hard to believe, but the airframe of a landing aircraft is now about as noisy as the engines. The noise generated by the airframe reduces very quickly as the aircraft speed is reduced, and the efficient airframe in the designs under consideration enables a low-speed approach. The low-noise designs have no flaps, a drooped leading edge rather than slats, and a simplified and streamlined undercarriage.