{"id":8564,"date":"2014-01-03T19:10:11","date_gmt":"2014-01-04T02:10:11","guid":{"rendered":"http:\/\/cafe.foundation\/blog\/?p=8564"},"modified":"2014-01-03T19:10:43","modified_gmt":"2014-01-04T02:10:43","slug":"quiet-may-be-the-new-black","status":"publish","type":"post","link":"http:\/\/cafe.foundation\/blog\/quiet-may-be-the-new-black\/","title":{"rendered":"Quiet May Be the New Black"},"content":{"rendered":"

Noisy airplanes are the bane of modern living.\u00a0 (Well, that and the myriad other intrusive sounds with which we are surrounded.)\u00a0 People can create and easily get signatures on petitions to close 70-year-old airports surrounded by 20-year-old housing developments, so General Aviation\u2019s survival will at least partly depend on hushing our aircraft.<\/p>\n

We\u2019ve been privileged to see and hear the passage of e-Genius, Pipistrel\u2019s G4, and Chip Yates\u2019 Long-EAS with a Craig Catto propeller<\/a>, which emitted a barely discernible howl when it pushed the airplane at full power to a new time-to-climb Guinness record at the California State Airshow in early October 2013, reaching 500 meters (1,640 feet) in one minute, four seconds.<\/p>\n

\"The<\/a>

The blades come this way, straining our sense of symmetry. \u00a0This is he 1\/5 scale test model<\/p><\/div>\n

This quest for quiet presses on the big airplane producers, too, anxious to be good neighbors and give passengers a less raucous flight.\u00a0 One engine make, Snecma, has been working on the problem since before 2009, when this report appeared in the blog Envirofuel<\/a><\/em>.<\/p>\n

\u201cVolvo Aero will help develop open-rotor aircraft engines for the EU\u2019s\u00a0Clean Sky<\/a>\u00a0project in conjunction with Rolls-Royce and Snecma. Open-rotor engines are essentially large turbofan engines without the ducting around the outside of the fan. In open rotor engines, the diameter will increase to more than double existing turbofan diameters, allowing the engine to work with a larger airflow, regardless of aircraft speed. This means that the energy turning the fan will be utilized more efficiently, thereby reducing fuel consumption by 15 to 20 percent.<\/p>\n

\"The<\/a>

The GE open-rotor concept tested in the 1980s was too noisy<\/p><\/div>\n

\u201cOpen-rotor is actually not a new concept. In the 1980\u2032s open-rotor engines were developed when oil prices rose to USD40 per barrel. When the oil price later dropped dramatically, plans were shelved. Sound familiar? Volvo say aircraft with open-rotor engines can be in the air by the end of the decade but engineers will have to reduce the noise that is normally contained by the turbofan ducts on modern jet engines.\u201d<\/p>\n

More recent attempts to realize the potential of an open-rotor engine have led to Snecma building a prototype<\/a> that will be tested on an Airbus A340 in 2019.<\/p>\n

Michael Gubisch, reporting for Flight Global<\/em>, explains the core of Snecma\u2019s M88 fighter plane engine will power two unducted, contra-rotating fans.\u00a0 Because the fans can be larger in diameter than those constrained by conventional turbo-fan engine, they can turn more slowly and push a larger volume of air.\u00a0 The demonstration unit should undergo ground tests in 2016.<\/p>\n

\"Open<\/a>

Open rotor as it might appear for NASA Glenn testing<\/p><\/div>\n

Snecma, an equal partner with General Electric in developing an engine for narrow-body passenger jets in a joint venture called CFM International, has been conducting wind tunnel tests on a one-fifth scale version of the engine at the ONERA (“The French Aerospace Lab”) research facility in alpine Modane, France.\u00a0 Noise levels are lower, and are helping Snecma, GE and NASA resolve to push forward with full-scale versions.<\/p>\n

Earlier attempts at producing an open-rotor engine produced much higher noise levels than conventional, ducted turbofans.\u00a0 Despite that, the open-rotor configuration was tested on a Boeing 727 and a McDonnell Douglas MD-80. \u00a0The video comes from a different time, where the difference between 50 cents per gallon fuel and $1.00 per gallon could have profound economic consequences.<\/p>\n