The Silent Aircraft Initiative is a study being undertaken by the Cambridge-MIT Institute

Cambridge-MIT Institute

The Cambridge–MIT Institute, or CMI, is a partnership between the University of Cambridge in Cambridge, England, and the Massachusetts Institute of Technology in Cambridge, Massachusetts....

 to discover ways to reduce aircraft noise

Aircraft noise

Aircraft noise is noise pollution produced by any aircraft or its components, during various phases of a flight: on the ground while parked such as auxiliary power units, while taxiing, on run-up from propeller and jet exhaust, during take off, underneath and lateral to departure and arrival paths,...

 dramatically, to the point where it would be virtually unnoticeable to people outside the airport

Airport

An airport is a location where aircraft such as fixed-wing aircraft, helicopters, and blimps take off and land. Aircraft may be stored or maintained at an airport...

 perimeter. Launched in November 2003, the program has the support of Rolls-Royce

Rolls-Royce plc

Rolls-Royce Group plc is a global power systems company headquartered in the City of Westminster, London, United Kingdom. It is the world’s second-largest maker of aircraft engines , and also has major businesses in the marine propulsion and energy sectors. Through its defence-related activities...

, Boeing

Boeing

The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...

 and Marshall Aerospace

Marshall Aerospace

The Marshall companies have been internationally associated with aerospace engineering for nearly a century. The company employs over 1,800 people and is based on an site with of covered hangar space...

.

Part of the study is examining if a steeper continuous descent into an airport will reduce approach noise levels. Theoretical analysis will be backed-up by field trials using real jetliners.

A major part of the study is developing jetliner/engine designs that can meet the SAI objectives. The favoured configuration is a blended wing design, with the engines located on the upper surface of the wing, to shield ground observers from the engine noise. A very low specific thrust (i.e. very high bypass ratio) turbofan

Turbofan

The turbofan is a type of airbreathing jet engine that is widely used for aircraft propulsion. A turbofan combines two types of engines, the turbo portion which is a conventional gas turbine engine, and the fan, a propeller-like ducted fan...

 is proposed for the aircraft. Engine handling and low jet noise are facilitated by the use of a variable area final nozzle

Nozzle

A nozzle is a device designed to control the direction or characteristics of a fluid flow as it exits an enclosed chamber or pipe via an orifice....

, to rematch the fan

Fan (mechanical)

A mechanical fan is a machine used to create flow within a fluid, typically a gas such as air.A fan consists of a rotating arrangement of vanes or blades which act on the air. Usually, it is contained within some form of housing or case. This may direct the airflow or increase safety by preventing...

. Acoustic treatment in the intake

Intake

An intake , or especially for aircraft inlet, is an air intake for an engine. Because the modern internal combustion engine is in essence a powerful air pump, like the exhaust system on an engine, the intake must be carefully engineered and tuned to provide the greatest efficiency and power...

 and exhaust ducting minimizes turbomachinery

Turbomachinery

Turbomachinery, in mechanical engineering, describes machines that transfer energy between a rotor and a fluid, including both turbines and compressors. While a turbine transfers energy from a fluid to a rotor, a compressor transfers energy from a rotor to a fluid...

 noise. Because the blended wing is too shallow to accommodate twin engines, a four engine configuration is proposed.

The study is funded by the UK Treasury

Treasury

A treasury is either*A government department related to finance and taxation.*A place where currency or precious items is/are kept....

and industrial partners.