Boeing and EADS are tussling for supremacy in the refuelling market. We look at the technology and production processes behind their programmes
Fifty years ago, Boeing created the concept of a jet tanker/transport with the Model 367-80, a privately funded venture that paid massive dividends by leading to development of both the 707 and KC-135. Now Boeing is converting the first 767 tanker for Italy, while simultaneously completing initial assembly of another privately funded jet tanker/transport - the 767-200C, a new baseline derivative that provides the foundation for the proposed USAir Force KC-767A, as well as a string of potential export customers.
With much of the groundwork for the 767 tanker effort already done under an Italian air force contract, and a similar Japanese programme, Boeing has tailored an enlarged programme around a "build-to-package" concept called the Global Tanker Transport Aircraft (GTTA). "The GTTA is a baseline programme that Boeing is funding," says Bob Gower, vice-president 767 tanker programmes. "It's like creating the catalogue and options for a car, and creates the 'core package' of modifications with STCs [supplemental type certificates], support data and so on," he says.
All 767 GTTA derivatives spring off this baseline 767-200ER, with different customers taking different options. The Italian air force, for example, is taking a support package, satellite communications and airstairs as options on top of the tanker modification which, in this case, is based on the convertible combi version of the 767-200ER. The modification includes an aerial-refuelling receptacle and a centreline refuelling boom, as well as wingtip hose-and-drogue pods and a centreline hose drum unit. The Italian aircraft is being configured to take either 19 463L pallets or 200 passengers, or 10 military 463L freight pallets and 100 passengers in combi mode. The first Italian tanker is due to begin flight tests late this year with delivery early in 2006, while the next "green" Italian airframe is due for delivery to Wichita, Kansas in May 2005.
US-Japan commonality
The Japan Air Self-Defence Force, on the other hand, is taking satcom and a support package from the catalogue. Unlike the Italian aircraft, the Japanese tankers will be based on the convertible freighter variant of the 767-200ER, and will be equipped with refuelling boom only. The non-combi configuration resembles the USAF baseline in being equipped for auxiliary fuel tanks providing a maximum fuel load in excess of 88,500kg (195,000lb), while retaining main deck space for 19 pallets or 200 passengers. This commonality gives Japan the potential to take advantage of the USAF programme when, and if, it gets the go-ahead.
"The Japanese have a high interest in trying to align with the USAF programme and so are currently evaluating whether to finish them here [in Wichita] or in Naples," says Gower. All the tankers will come off the Everett, Washington assembly line as "green" aircraft, with modifications following at either Boeing's Wichita site in Kansas or at Aeronavali in Naples, Italy.
Although Italy's first tanker is undergoing conversion in Wichita, the three subsequent aircraft will be flown directly from Everett to Naples for conversion. The Japanese aircraft, because of commonality with the USAF configuration, are expected to have the bulk of the baseline modifications incorporated "in-line" at Everett, with completion at either Wichita or Naples. The first Japanese 767 airframe will be completed in Everett in May 2005 for modification. Delivery is due in late 2006 with service entry in the first quarter of 2007, with subsequent tankers arriving in Japan every year until 2010.
The USAF KC-767A tanker also springs off the GTTA, but because of the more extensive changes requires certification as an entirely new -200C sub-model of the 767. "The USAF aircraft builds on the GTTA to launch a new minor model at Boeing Commercial Airplanes," says Gower. While retaining the overall dimensions and performance characteristics of the -200ER, the-200C incorporates the heavier-gauge flaps, strengthened main landing gear and digital flightdeck of the 767-400ER, and a variety of other structural and system adaptations including engine-mounted 120kVA integrated drive generators and tail-mounted 120kVA auxiliary power unit. Powered by Pratt & Whitney PW4062 turbofans, the auxiliary-tank-equipped -200C will initially be certified with a maximum take-off weight of 179,330kg versus the highest gross weight of 175,540kg available on the commercial -200.
Despite the issues that have stalled the US tanker programme, the first -200C is rolling down the Everett production line and is due to emerge complete by early June. Boeing remains optimistic that the suspended USAF contract will be reinstated, and that flight tests can begin. But with more than $300 million of company money already spent, and design work on hold pending the outcome of the Department of Defense's investigations, Boeing says the one-off aircraft may well be sold, possibly to a VIP customer, if the tanker programme is again delayed or even cancelled.
Tanker of choice
For the mid- to long-term, Boeing insists that the 767 remains its choice for the next USAF tanker. The recently launched 7E7, although a 767 replacement, is designed for long-range point-to-point routes and is unsuitable for the tanker mission, says Boeing senior vice-president and general manager air force systems, George Muellner.
"The issue is not composites, but its configuration," he says, adding that futuristic tanker concepts such as the blended wing-body will not be available until "2015 at least". Focus remains on the 767, says Muellner, who adds the "spiral development" potential of the KC-767A makes it "much more than just a tanker". The USAF "wants a 'smart' tanker, which will work as a communications node in the network, and a relay for ground communications systems."
Although initial tankers for the USAF are to be provisioned only for single-aircraft refuelling, Spiral 2 aircraft will also have wingtip refuelling pods. Boeing also foresees upgrades to enable refuelling of unmanned air vehicles, which will require methods of stabilising the boom and drogue in turbulent air. The company is considering a recently patented Smiths Aerospace design, which is to be windtunnel-tested this year . Longer-term plans include development of a next-generation boom that will expand the operational envelope for connecting with a single receiving aircraft. Potential future improvements include drag-reducing Aviation Partners Boeing winglets and revised hydraulic systems.
If the USAF deal goes ahead, Boeing plans to "ramp up production to 13 a year almost immediately, and over two years it would get up to 20 a year", says Gower, who cautions that with the current delay it will be "slightly less than three years from contract to aircraft on the ramp. The longer we are in the 'pause' the longer it will take to ramp up." Remaining optimistic that the USAF will be allowed to go ahead with the purchase and/or lease of the aircraft, he adds: "We are in the tanker business and this is a big opportunity for us. We've supplied all the tankers to the USAF to date, and our goal is to continue doing that."
GUY NORRIS / WICHITA
Source: Flight International
