Is bigger always better? This is at the heart of the battle between Boeing and Northrop Grumman for the US Air Force's $40 billion KC-X tanker contract, which is set to be awarded within weeks. Risk, cost and jobs are other factors the companies hope will differentiate their bids.
Although the final proposals have been submitted, EADS upped the jobs stake last week by committing to assemble Airbus A330F commercial freighters in the USA if Northrop's A330-based KC-30 is selected. This could more than double the number of aircraft assembled in Mobile, Alabama to 48 a year, including 12-18 tankers.
A Defense Acquisition Board review of the KC-X programme has been scheduled for 13 February, with industry expecting the winner to be announced within 10 days after that meeting. The contract is for 179 aircraft to begin replacing the USAF's 530 KC-135s
Boeing argues its KC-767AT is the right size for the US Air Force's requirement for a KC-135 replacement that is "first and foremost" a tanker. Northrop claims the larger, KC-30 offers "the lowest risk and most capability at comparable cost".
Northrop says the KC-30 offers more effectiveness as a tanker as well as greater cargo and passenger capability. Boeing questions whether the USAF could and would make use of that extra capability in the initial tranche of replacements for its ageing KC-135s.
"The aircraft are too valuable," believes retired USAF chief of staff Gen Ron Fogelman, now a consultant to Boeing. "Secondary attributes are important, but not critical to a tanker. This fight should not be won based on secondary attributes," he argues.
Northrop's air mobility sector vice-president Paul Meyer says the KC-30's greater fuel offload capability provides a higher "fleet effectiveness value" (FEV) in the refuelling role. FEV is one of the five source-selection evaluation criteria defined by the USAF.
Calculated over five mission scenarios specified by the USAF and using prescribed airbases, ramp space and resources, Meyer says the FEV figure calculated by Northrop and submitted with its KC-30 bid is 1.62 (the KC-135 representing an FEV of 1).
Northrop calculates an FEV of 1.35 for the rival KC-767, but Boeing has not released its number. Instead the company says the KC-767 offers greater military utility because more smaller, lighter tankers can operate from more airbases and shorter runways.
Each argues the other represents the higher risk. Northrop says it bid is baselined on the KC-30B now in flight test for Australia, with the same cockpit, engines and refuelling boom. Meyer argues Boeing's bid is risky because it is based on a version of the 767 not yet built, combining the -200ER fuselage, -300F wing, gear and cargo door and floor, -400ER digital flightdeck and flaps, uprated engines and "sixth-generation" boom.
Boeing vice-president tanker programmes Mark McGraw says the cost to certificate and produce this "tailored" version of the 767 is "included in the price quoted us by Boeing Commercial Airplanes" and therefore factored into the cost quoted for KC-X. But Boeing believes the KC-767 still offers the lowest "most probable life-cycle cost" - procurement and operating costs over 20 years - another of the USAF's five source-selection criteria.
While Northrop believes the KC-30 has a "comparable unit cost" to the KC-767, Meyer acknowledges its life-cycle cost will likely be higher because the larger aircraft burns more fuel and costs more to maintain. But he believes the KC-30's greater capability will offset the higher cost when the USAF comes to assess best value.
Boeing, meanwhile, sees risk in the plan by Northrop and EADS to transfer production of the KC-30 from France to the USA. Final assembly is to be performed by EADS North America in Mobile, and completed aircraft rolled across the runway to a Northrop facility for modification to military tankers. Boeing argues this is inherently inefficient compared with the KC-767 build plan and "adds time and complexity to production".
Meyer says the plan is on track, with EADS committed to build the four development aircraft as commercial assets. The first of these is complete and waiting to be flown to Dresden for installation of the cargo door. "We are holding off fitting the door until we have a contract so that the aircraft can still be sold to a commercial customer," he says.
According to the plan, the three remaining development aircraft (D2-4) are scheduled to fly in May 2008 and January and May 2009. After contract award and door installation, D1 will fly to Madrid for tanker conversion. D2 and D3 will be converted at Northrop's facility in Melbourne, Florida. D4 will be the first converted in Mobile. Beginning with the first production KC-30 cargo doors will be installed in Mobile and from the second production aircraft onwards, Meyers says, final assembly will be performed in the USA.
Both sides are taking pot shots at each other's past performance, another evaluation criteria. Northrop highlights delays to deliveries of KC-767s to Italy and Japan while Boeing points to slippage in delivery of boom-equipped KC-30Bs to Australia. But risk and cost aside, size is still the issue for KC-X.