Boeing must perform on the new KC-46 tanker programme, the US Air Force is warning the company as the aircraft enters its preliminary design review (PDR). Otherwise the service could walk away.

"We could buy more KC-46s or - make no mistake about it - if Boeing doesn't perform, we'll just start another competition," says Maj Gen Christopher Bogdan, the USAF's KC-46 programme executive officer.

Boeing KC-46,

 © Boeing

The KC-46 represents the first step in the USAF's plans to replace its ageing fleet of Boeing KC-135 tankers

The KC-46 effort is the first phase of a three-step programme to replace a geriatric fleet of 416 Boeing KC-135 tankers that have been flying since the Eisenhower administration.

The USAF wants a total of 179 KC-46 tankers eventually, but initially Boeing is obligated to deliver the first batch of 18 combat-ready KC-46As by August 2017.

The first production aircraft deliveries are expected in early 2016, Bogdan says.

"If they don't give us the 18 airplanes by August of 2017, I have the option to withhold payments [and] I have the option not to approve any of the further production options," Bogdan says.

With a production rate of 15 aircraft per year, Boeing will be building the KC-46 until 2028. But the contract has a mechanism to vary production rates. For example, in years three, four and five, the USAF has the option of buying between nine and 18 jets and would still get good prices, Bogdan says. "We got a really, really good deal," he adds.

However, 179 aircraft will only cover the replacement of 33% of the KC-135 fleet. If Boeing fails to deliver on the contract or the USAF is not happy with the aircraft, the service has the option to start the follow-on KC-Y and KC-Z tenders early, Bogdan says.

But pressuring Boeing to perform is not the only reason for the relatively small order: technology is likely to have evolved by 2028, when the last production KC-46 from this buy rolls off the production line.


Moreover, the threats the USA will be facing by then might be very different and there new requirements may have to be incorporated. While it is not part of the current requirements, the KC-46 cannot refuel unmanned aerial vehicles. In the future that would almost certainly be a requirement, Bogdan says.

"We wanted to have the opportunity later on down the road to incorporate any of that in a new design," he adds.

Keeping open the prospect of two additional contests also provides an incentive for Boeing and competitor EADS to keep investing in and developing new technologies for a future tanker design.

As such, the USAF strategy is to maintain a level of ambiguity about its plans for follow-on competitions.

"If it were up to me today, I would tell you that I want to keep it vague as to what we do for KC-Y," Bogdan says.

Boeing KC-46

 © Boeing

The KC-46's refuelling boom is a new version of the KC-10 tanker's boom, modified with a digital fly-by-wire system

The threat of walking away from the contract is not the only stick the USAF has in its arsenal as it prods Boeing into maintaining discipline on the KC-46. The contract is structured so that the USAF's liability is strictly limited.

Boeing has to pay for every penny the KC-46 project goes over the contract-ceiling price for the engineering and manufacturing development (EMD) phase.

Although the KC-46 programme is a $4.4 billion fixed-price incentive development contract, it limits the government's liability for costs over $4.9 billion.

The tanker's estimated development costs are currently around $900 million higher than the February 2011 contract award value, but the USAF is liable for only about $500 million of this total. The remaining $400 million is Boeing's responsibility.

"It's no surprise to us that the programme has hit the ceiling because we already planned for that and we already budgeted for that," Bogdan says. "The only surprise is that Boeing told us that so soon, quite frankly."

The KC-46 contract has another unusual feature. Unlike for the Lockheed Martin F-35 Joint Strike Fighter programme, US taxpayers are protected from concurrency costs.

Boeing is obligated to incorporate any modifications that may arise as a result of problems found during flight-testing or operational testing into the production line at its own cost. But it also must retrofit those modifications to any previously delivered jets without any additional cost to the USAF.

"In other programmes, once the airplane is delivered, if there is a problem with it, then it's the air force's issue to get it fixed," Bogdan says. "Not so on this contract."

By contrast, on the F-35 programme the US Department of Defense was forced to slow down production of the fighter because of the enormous cost of retrofitting early model aircraft rolling out of the factory.

However, the KC-46 tanker programme cannot take sole credit for developing a more favourable contract vehicle for the new aircraft - the DoD has learned over the years from previous efforts.

"We took a lot of good ideas from a lot of people," Bogdan says. "We just kind put it together in a way that all fits."

Analyst Richard Aboulafia of the Teal Group in Fairfax, Virginia, says the USAF had a decade to work out the details of the KC-46 programme. As such, he is not surprised that it is being well executed.

Contracts such as the KC-46 effort are part of a broader move by the DoD to shift more of the risk to contractors. "To a certain extent this is the future," he says.

But this type of fixed-price contract does not work for a new clean-sheet developmental effort. "There is all sorts of mayhem that can be produced by an all-new clean-sheet-of-paper design," Aboulafia says. "Especially for a combat aircraft where you have three services weighing in."

Bogdan agrees: "I wouldn't tell you that every programme could be like this, because we're using a commercial derivative airplane."

Meanwhile the KC-46 has entered its PDR phase, which is split into two phases.

"The first step has already occurred," Bogdan says. "That's where we jointly with Boeing reviewed the entrance criteria to kinda start the PDR review."


That review started in the week of 18 March and Bogdan says he spent three days at Boeing's facilities reviewing 89 criteria for the PDR. Those criteria range from manufacturing plans to the minutiae of the integrated designs for the aircraft's fuel system. "We went through one by one to make sure Boeing met the criteria for the government to say: 'Yeah, that's good enough to move on to PDR.'"

What is unique in the case of the KC-46 is that the USAF jointly reviewed those requirements with Boeing. That afforded Bogdan the opportunity to hear from both Boeing and USAF experts at the same time and gave him a broader understanding of the PDR details, he says.

"As far as I can tell right now in my assessment of that, Boeing met all 89 of those criteria," Bogdan says.

Boeing KC-46,

 © Boeing

The next step will take place during the last week of April. There are eight exit criteria for the programme to move out of the PDR stage.

"The most stringent of those is [that] all the sub-systems on the airplane have to go through their own individual mini-PDRs and then they have to be rolled up into a big, integrated 'here is the preliminary design of the airplane'," Bogdan says.

Assuming Boeing meets the USAF's requirements, the service will clear the company to start detailed design of the new tanker. That process of detailed design, integration and assembling manufacturing drawings should take roughly 13 months.

The next step after that would be the critical design review (CDR) that is currently scheduled for July 2013.

"Once you get to CDR, you should have significant drawings completed so they can start building the first test articles," Bogdan says.

Boeing will build four test aircraft for the KC-46 programme at its factory in Everett, Washington. The first two aircraft are new versions of the venerable 767 called the 767-2C. The new model will have a cockpit derived from Boeing's state-of-the-art 787 airliners, a fully stressed cargo floor and a cargo door. The entire aircraft has a "beefed-up structure", Bogdan says.

"Those will undergo FAA [US Federal Aviation Administration] testing," he says. That will include an "amended type-certification testing and supplemental type-certification testing."

Boeing is contracted to deliver an aircraft with a FAA type-certificate. There are two parts to this requirement: firstly, the baseline 767-2C must first get its amended type-certificate (ATC), as all new variants of existing civilian aircraft must. Secondly, the jet must also get a supplemental type certificate (STC) for all of its various military modifications.


The USAF could simply issue a military type-certificate, but then the service could not use the testing already done by civilian users. This would make operating the plane more expensive.

Boeing, in partnership with the FAA, is efficient at testing new civilian aircraft, but testing military aircraft is a far more complex endeavor - which might cause delays.

The first flight of the 767-2C is expected in the summer of 2014.

The next two aircraft will be built as 767-2C aircraft but will immediately begin modifications to turn them into true KC-46 tanker flight-test articles at another plant in Everett. The aircraft is being designed to offload 212,000lb of fuel and double as a cargo transport. The aircraft is also being designed with a 40-year lifespan.

Earlier Boeing plans to install military hardware in Kansas were shelved when the company decided to shut down its Wichita facilities.

If all goes according to plan, the first KC-46 will fly in January 2015.

Boeing KC-46,

 © Boeing

On the KC-46, the USAF and Boeing have to integrate military and civilian software

"We'll have four airplanes in the test programme," Bogdan says. "Two of them initially focused on FAA testing and two of them initially focused on military testing."

But there are several potential problem areas as the KC-46 navigates though development and tests. Of these, software development and integration is one area Bogdan is particularly worried about. Indeed software development and testing has bedevilled many prominent programmes including the Lockheed Martin F-22 Raptor and the F-35.

"I've never been on any aircraft programme - and I've been in acquisitions for 25 years - where software shouldn't be a major focus and doesn't cause some kind of disruptions," Bogdan says. "I made that an emphasis item from the very first day on this programme."

On the KC-46, the USAF and Boeing have to integrate military and civilian software, which can be challenging. However, Boeing has taken some steps to mitigate potential problems, including setting up three dedicated software integration labs (SILs).

"That's really good because other programmes I've been on have sometimes had to share time in a software integration lab with other programmes," Bogdan says.

Moreover, one of those labs will be a full-up hardware and software-integrated pilot-the-loop rig, which will allow the KC-46 programme to do much more realistic testing on the ground. "You don't want to find problems necessarily on the test airplanes," Bogdan says. "You'd rather figure them out in the SIL."

The USAF has also mandated that Boeing use the Department of Defense's "best practice" guidelines for software development and for the metrics with which they benchmark their performance. "We've also made sure that those practices and processes have been slowed down to their sub-tier software suppliers," Bogdan says.

On the manufacturing side, the USAF is hoping that Boeing will be able to leverage production experience on the cargo variant of the 767 - which has many of the same features as the KC-46.

Those features include the cargo door, cargo floor and much of the airframe, Bogdan says. As much as 80% of the KC-46 is derived from civil hardware that is common to Boeing commercial aircraft. "So there is obviously some synergy for Boeing there," he says.

Federal Express has ordered 30 Boeing 767-300F freighters, which will help mature the production line for the service's next-generation tanker.

"The other good thing for our programme is FedEx is going to get delivered their cargo freighter airplanes before ours," Bogdan says. "That means Boeing's going to have to mature the production line for that airplane before our airplane goes down the production line."

That should also help reduce the risk to the USAF flight test programme.

"That's a very good risk reduction for us," he says. "There will be lessons learned from the FAA testing that Boeing's got to do for the model version of the FedEx airplane."

But there are other aspects of the KC-46 development and test effort that might prove to be more difficult.

The KC-46's refuelling boom is a new version of the Boeing KC-10 tanker's boom, but it has been modified with the digital fly-by-wire system found on Italian and Japanese 767 tanker booms.

"We're integrating old software on old hardware," Bogdan says. "That always creates some risk, but I think they're both known quantities."


Unlike the KC-10 or the older Boeing KC-135 tanker, the boom operator does not refuel aircraft by looking through a physical window. Instead that operator looks at a 3D video-display system similar to modern cinemas - not unlike the movie Avatar.

Last December in Saint Louis, Missouri, Boeing built and test flew the 3D-display and associated optical and infrared cameras on a Hawker-Beechcraft King Air aircraft. USAF and Boeing boom operators proved that the sensors and displays both work by conducting mock aerial-refuelling with Boeing F-15s and F/A-18s.

"Although that's a prototype, and although it's not on the KC-46," Bogdan says, "we know they can integrate the sensors, the screen and all that software."

However, the KC-46 is also required to support the US Navy's hose-and-drogue refuelling system though wing-mounted refuelling pods. Boeing had encountered difficulties with aerodynamic buffeting on the Italian 767-based tanker's pods and has instead picked Cobham to build the KC-46 pods. Cobham had the engineering expertise needed to change the outer mould-line of its pods to tailor them to the requirements of the USAF tanker, Bogdan says.

Boeing KC-46,

 © Boeing

"They already reshaped the pod," he says. "The buffet problem that they saw on the Italian tanker has been pretty much mitigated."

If there are further problems, Cobham has the ability to reshape the pod again if a problem is discovered in testing - which is not true of the other pod-maker, Bogdan says.

The USAF test programme will run until the end of 2017. The last major event prior to the KC-46 joining the combat air forces is operational testing, which will happen that year.

But recent reports from both the Government Accountability Office and J Michael Gilmore, the Pentagon's director of operational test and evaluation, say that Boeing and the USAF are underestimating the difficulty of flight-testing the KC-46. Both decry the level of concurrency in flight tests between the FAA certification and the military flight tests.

Bogdan says the two reports are overstating the problem. He says that the risks are mitigated because most of the systems on the KC-46 have flown in one form or another on other aircraft. Moreover, much more of the flight-test programme will be completed before the tanker heads to production than for previous military aircraft.

"We're going to have over 60% of all of our flight-testing completed before we ever give the permission to start production," Bogdan says. "That's an awful lot of testing compared to most other programmes."

In another break from tradition, the KC-46 production start is not based on a specific calendar date. Boeing has to meet certain criteria tied to successful flight-testing. The longer it takes to get the KC-46 into production, the longer it will take for the company to make a profit on the programme.

"It's an event-driven requirement," Bogdan says. "If they don't get that flight-testing done and are successful, I won't give them permission to start production."

Boeing declined to comment for this article when contacted.

Source: Flight International