Boeing confirms the General Electric GEnx engine family is among the propulsion systems it will consider for a new KC-X tanker proposal based on either the 767- or 777-series airliners.

The surprise inclusion of GEnx, which powers the 787 and 747-8, among its engine choices signals a new level of flexibility for Boeing's approach to both propulsion suppliers and platforms to fulfil the US Air Force's still undecided requirements for a KC-135 tanker replacement.

If Boeing's previous tanker campaign was characterised by a single-minded advocacy for a 767-200LRF powered by a Pratt & Whitney PW4062, its third attempt to win the KC-X contract is being carefully shaped to preserve its flexibility to the USAF's requirements.

"It's not about us," says Chris Raymond, Boeing's vice-president for business development. "It's about what they decide to put in their requirements."

The dramatic change in tone comes after USAF officials briefed Boeing on what things the company should change about its approach to the competition, says Dave Bowman, Boeing's vice-president for tanker programmes. "And we listened to what they told us," he adds.

The USAF plans to release a draft request for proposals in July or August, which should provide their first glimpse of the requirements that will shape Boeing's response.

Bowman says Boeing's 7A7 tanker concept encompasses all of its aircraft models, but his comments singled out the 767 family and the 777-200ER, in particular.

Sharply departing from claims in the previous competition, Bowman says a KC-777 can be developed on a similar timeline and budget as a KC-767.

The 777 option should offer Boeing a size advantage over the smaller A330-200 being proposed by the Northrop Grumman/EADS North America team.

Bowman notes, however, that if the USAF prefers more flexibility, a 767 model could be the best fit.

"It's an interesting fact that bigger isn't always better," Bowman says.

Meanwhile, GE confirms that GEnx-1B and -2B are in the correct size class for the tanker competition, but adds that there has been no official agreement with a manufacturer.

Source: Flight Daily News