Wednesday, June 29, 2011

The Dreams And Reality Of A Future Airliner

The Dreams And Reality Of A Future Airliner: "

At the Paris Air Show last week one of the biggest stories was the future of the smaller airliners. And while the focus was firmly based on the reality of what will be flying next, there was some talk of what could be flying many years in the future. And that discussion included a debate about propellers.

Airbus received a lot of attention for its record setting orders for the A320NEO, the latest version of its single aisle airliner. On the Boeing side, the company kept its stance of keeping quiet on what it will be doing to replace the current version of the popular 737. At the air show the company did not say whether it will be putting new, efficient engines on the existing airplane similar to what Airbus has done with the A320, or if it will start with a clean sheet and design an entirely new airplane.

In addition to the reality of what the next generation of airliners will look like, there was some dreamy talk about what an airliner might look like several decades from now. Airbus kicked off the show with sketches of an airliner with a transparent fuselage (above) and seats that conform to a passenger’s body. But somewhere in between the reality of next year and the dream land of airplanes decades away (if ever) are ideas that have been developed, but have yet to be implemented.

One of the ideas that has been tried in the past and continues to be an idea mentioned with efficient airliners of the future is the unducted fan, or propfan. The idea first made headlines back in the mid 1970s when fuel efficiency was also quite popular.

A NASA/GE unducted fan idea from the 1980s.

The basic design idea is to combine the speed and performance of a modern turbofan jet engine, with the efficiency of a propeller. Any airplane flying with an unducted fan would likely be slower than a modern airliner, but there could be significant fuel savings.

The idea was tested on some existing airplanes back in the 1980s, including a 727 where the unducted fan replaced one of the three engines on the tail. But a wide range of issues including noise and how to contain a “blade-out,” the problem of a propeller blade being lost from the engine and potentially damaging the airplane. Current jet engine designs must be able to contain a lost blade without it leaving the engine cowling.

In Paris last week, the topic of unducted fans was once again raised with reference of what Boeing will do to replace the 737. According to the Seattle Times, Airbus executives believe there isn’t the justification for an all new design until an unducted fan design can be implemented. It went with simply adding new, efficient engines to the A320.

But Boeing told the newspaper it doesn’t see a solution to the blade-out problem anytime soon, making it unlikely we’ll see one on the 737 replacement.

It is possible the replacement for the 737 could be similar to the 787 Dreamliner, using composites and an efficient new design to complement new engines similar to those already being used. Boeing is expected to announce its decision on the replacement of the current 737 some time later this year.

Photos: Airbus, NASA


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