Cool and unusual

FlightGlobal.com reports that American Airlines is looking for a 150-seat narrowbody aircraft to replace its fleet of MD-80s and 757s. The engines for this new short-haul fleet will need to make less noise, consume less fuel, and produce a lower volume of emissions. CFM (the GE / Snecma joint venture) and Rolls Royce are considering open-rotor technology for their next generation jet engines. Instead of the fan blades being inside a cowling, they'd be exposed. (Here's a photo of an open-rotor engine.)

This technology, and the promise that this could give a 25% to 30% improvement in efficiency, "seems to be really a paradigm shift in fuel consumption", says [American Airlines executive VP of operations Bob Reding].

He notes, however, that questions still need to be answered concerning the maximum cruise speed that aircraft can fly with open rotors, the noise characteristics and certification requirements.

"There will probably be some blade-out requirements," says Reding, adding that since certification requirements are not yet written "that is certainly one of the unknowns and certainly one of the issues that will have to be addressed".

By "blade-out" I think he means, "What happens if a rotor blade breaks off and goes spinning through the air like a ninja's throwing star?" Given that the United Air Lines DC-10 Sioux City crash was caused by fan blades from a cowled engine severing the hydraulic lines to the control surfaces, that could be an important thing to test.