Airbus looking at Tri-Jets

Haven’t posted for a while, but saw this and thought it might be of interest to some of you….

Airbus applies for US patent for new trijet design
Stephen Trimble, Washington DC (17Apr08, 22:21 GMT, 393 words)

Reviving curiosity in an airliner type abandoned by manufacturers for nearly two decades, Airbus has filed a patent application for a new commercial trijet.

The patent application, published by the US Patent and Trademark Office on 27 March, shows a new trijet design featuring a distinctive, noise-shielding tail structure.

A US-based Airbus spokeswoman downplayed the design’s relevance in the airframer’s future plans.

“Airbus is regularly filing patent applications and this is normal business for a company that is a leader in innovation and technology,” she says. “That’s not to say this is ‘the’ design we’re looking at in the future – just one of a very many possibilities.”

Two trijets – Lockheed’s L1011 Tristar and the McDonnell Douglas DC-10 – led the long-haul widebody market in the 1970s, but the type’s long-term popularity was limited by excess cabin and environmental noise created by the aft-mounted engine, as well as the extra fuel burn.

More powerful – and reliable – engine designs allowed airframers to safely shift to twin-engine types for long-haul flights, leaving only four-engine aircraft as the only multi-engine widebodies still in production.

The Airbus patent filing, assigned to inventors Olivier Cazals, Jaime Genty De La Sagne and Denis Rittinghaus, argues that a new type of trijet can become viable again in the future.

Twin-engine aircraft are burdened by turbofans with “ever-increasing mass and size, thereby making it necessary for the aircraft structure (fuselage, wings and landing gear, in particular) to be designed accordingly,” states the patent application.

The Airbus inventors claim a trijet can compete against twin-engines by using a tail-structure that doubles as a noise shield. Exhaust from the aft-mounted engine enters a channel framed by upwardly-inclined horizontal stabilizers laid out in a “very open V” and the two fins.

This design “makes it possible to considerably reduce the previous acoustic problems, since the noise generated by the third engine of the fuselage is sucked up by the channel,” the patent document states.

The tail structure and the third engine also add weight and new structural complexity, but the Airbus inventors counter that the trijet can still beat a twin-engine type on fuel efficiency through offsetting improvements.

The added weight of the tail “is largely compensated for by the drop in the mass of the landing gear, the reason being that the landing gear is dimensionally smaller and less voluminous given the smaller engines.”

Source: Air Transport Intelligence news