Recently published patent application reveals manufacturer's design studies and innovations for high-speed airliner

Boeing appears to be struggling to keep airlines interested in its Sonic Cruiser concept over a more conventional alternative. It plans to make detailed presentations on "the value of speed" to a gathering of potential launch candidates in late October in its efforts to secure board authority to offer the high-speed airliner in early 2003.

The meetings, set for 23-24 October, will also include more detailed presentations on "other options" including the baseline "reference" aircraft which has attracted more interest from airlines than expected, thanks largely to its high efficiency levels.

"There are still three variants we're talking to airlines about, and by the end of the year we will hopefully be able to get more of an idea about which one we will focus in on," says Boeing.

Options include two main Sonic Cruiser designs - aft-wing and mid-wing versions - and the high-technology, conventionally configured reference aircraft formerly dubbed Project Yellowstone. Sources close to the programme say Boeing's Sonic Cruiser marketing initiative has lost headway because of the slower-than-expected recovery of some key US operators which now favour concepts that push economy rather than speed.

New design details of the Sonic Cruiser have recently emerged in patent documents. The patent, which includes supporting details of previous Boeing supersonic and transonic design concepts, covers the integration of the aft body with a delta wing and rearward tapering fuselage, along with designs for an integrated propulsion system with s-shaped inlets.

The patent also includes interior arrangements for waisted (area-ruled) and non-waisted fuselage configurations, various tail and aft body configurations and even a scaled, business jet version of the Sonic Cruiser.

Although the patent does not include definitive data on the configuration of current mid-wing concept studies, they are understood to borrow elements from previous design studies detailed in the document. The diagram below illustrates what the mid-wing concept might look like, based on information obtained by Flight International.

Several design innovations are outlined in the patent. These include: "beaver" tails inboard of the exhaust nozzles that provide structural support for the nacelles and act as integral horizontal stabilisers; cross-sectional area reduction achieved through the aft-wing configuration, negating the need for fuselage waisting and at the same time allowing the overall length of the propulsion system to be increased without substantially increasing structural loads aft of the wing trailing edge.

Advantages for the integrated propulsion configuration include the ability to mount larger bypass engines without significant aerodynamic penalty, and a reduction in the wetted area and resulting friction drag, says Boeing. The s-shaped inlet is also expected to shield the fan-generated noise.

Source: Flight International