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Sonic Cruiser - Boeing's Mystery Ship!

AT THIS year’s Farnborough Show, doubt began to circulate among industry observers and the Press as to the efficacy of Boeing’s much proclaimed future commercial airliner project, the Sonic Cruiser. The underlying impression was that the Mach 0.98 aircraft is nothing more than a smokescreen for a totally different design in the 250-seat range with a changed appearance to that currently put out by the Seattle giant. In fact, there was little on which to base such an assumption. Boeing continued to remain tight-lipped on the design while at the same time placing and announcing contracts with a number of ancillery companies to assist with the development of the project.

Boeing chairman Phil Condit said, ‘We are after a program with broad attractiveness and a long life. The technology is there, but we need to understand the market first’. Indeed, the market is the driver of the Sonic Cruiser and the project was just one of many future ideas which took a hard knock following the September 2001 terrorist attacks. The subsequent steep plunge in air traffic left many of the large airlines reeling. Huge investment in new airliners and no money to pay for them meant that planning for a new technologically advanced aircraft was a long way from most of their thoughts. Fortunately, the down-turn appears to have ‘bottomed-out’ and the airlines are now looking again at their future and what they will need in service.

At Farnborough, Walt Gillette, v-p and program manager for the design said, “We are making very good progress on the fundamentals required to create the Sonic Cruiser. These fundamentals involve the technology needed for the airplane, the processes needed to create the airplane, and the basic configuration exploration activities necessary to reveal the very best shape for the airplane.” Gillette characterised the current phase of development as a “learning” phase and said that progress is measured by how fast the team is learning about the technologies, tools and processes that allow it to create an all-new class of flying machine.

Advancements in computational fluid dynamics (CFD), the computer coding used to evaluate and develop the aerodynamic flows of structure, have been instrumental in allowing rapid learning on the Sonic Cruiser program. Gillette noted that a second round of wind tunnel tests continues to verify that the CFD coding is predicting performance to within 1%. “That means we can do a lot of learning before we ever get to the wind tunnel.” He said “We’ve looked at more than 25 wing planforms, 50 nacelle shapes and 60 fuselage designs in the past 16 months. We could never have done that on earlier programs.”

A future canard design

The first public announcement of the Sonic Cruiser was made on March 29 last year when Boeing revealed the dramatic new design. It said that today’s passenger wants more long non-stop flights, faster and with more comfort. It would have to result in an aircraft with low noise, low emissions and no sonic boom. Boeing would therefore pursue a totally new idea for a 200ft-long 225-250-seater with a cruising speed of Mach 0.96 at around 45,000ft. A launch date was subsequently proposed for the end of 2002 with production aircraft entering service with the airlines in 2008. Boeing has since claimed that revealing such a major programme so early in its life meant that the baseline configuration had yet to be decided, hence the reluctance to talk more fully about the proposal.

As far as shape is concerned, recent artist’s impressions and models still show a canard-equipped, aft-wing design, but the original inward-canted fins are now swept and upright with some cosmetic changes around the engine pods and underwing intakes. The wing tips are highly swept and the canards have a marked dihedral. That configuration is as they say, ‘open source stuff’. More discreet are the other options being studied and it is this area which has fuelled speculation that what you see is actually not what will fly.

Boeing’s studies into the Sonic Cruiser project still centre on the aft-mounted wing and canard layout, seen above left and right and in the only wind tunnel view released (below). Behind the scenes, however, other designs are still under serious consideration. (All photos, Boeing).

For the rest of this article please see the October issue.