Posted on January 11 2022
The Boeing KC-46A Pegasus is a U.S. air-refueling tanker based on the commercial Boeing 767 airliner. The aircraft will replace the KC-10 and partially replace the KC-135 in U.S. service. A total of 179 aircraft are on order for a total program cost of at least $44 billion with $34.9 billion in procurement and $6 billion in research, development, test and evaluation (RDT&E) funds. As of the time of this writing, the KC-46 has two foreign military sales (FMS) customers: Japan and Israel. As of the time of this writing, 52 KC-46As have been delivered to the U.S. Air Force and a single example has been delivered to Japan.
The KC-46’s genesis began from a 2001 U.S. Air Force (USAF) effort to lease 100 tankers to replace the service’s oldest KC-135s. Northrop Grumman partnered with EADS (Airbus) to offer the KC-30 based upon the A330 Multi-Role Tanker Transport (MRTT) while Boeing offered a modified KC-767. The USAF awarded Boeing a $20 billion contract in 2003 but the program was suspended in December over allegations of misconduct on behalf of a senior USAF official charged with overseeing the program. The contract was ultimately canceled in 2005 and the USAF proceeded to completely restructure its tanker recapitalization strategy.
The Air Force published a “tanker roadmap” in 2006 that called for a three-step replacement for a then-combined fleet of over 500 Boeing KC-135 and KC-10 tankers. A “KC-X” contract award for the first 179 aircraft would be succeeded by a follow-on “KC-Y” contract 15-20 years later. Finally, a “KC-Z,” representing a purpose-built refueling system, would come last. In April 2006, the USAF completed an analysis of alternatives validating the plan. The initial request for proposals was released in January 2007.
Northrop Grumman paired with EADS to again offer an MRTT derivative (KC-45) while Boeing again offered a KC-767 derivative (KC-46). Airbus planned to open an MRTT modification and assembly line in Alabama as part of its proposal. The USAF selected Northrop’s KC-45 in February 2008 but Boeing protested the award to the Government Accountability Office (GAO) that March. The GAO sustained Boeing’s protest in June 2008 stating, “The Air Force, in making the award decision, did not assess the relative merits of the proposals in accordance with the evaluation criteria identified in the solicitation, which provided for a relative order of importance for the various technical requirements”.
Source Selection Evaluation Team (SSET) ratings for each respective bid and Integrated Fleet Aerial Refueling Assessment values. Credit: GAO
Following the GAO ruling, the DoD suspended the KC-X competition and effectively deferred the issue to the Obama Administration. In September 2009, both the USAF and the DoD announced the third tanker recapitalization effort would feature greatly refined selection criteria and a rigorous contracting strategy. Critically, the Engineering Manufacturing Development (EMD) phase would feature fixed price inventive fee contract with a ceiling value. Lots 1 to 5 production would utilize firm fixed-price contracts with the final 111 aircraft using a not-to-exceed value contract structure. In December 2009, Northrop CEO Wes Bush announced the company would not participate in the relaunched tender citing financial burdens and the current RFP favored Boeing. Airbus ultimately opted to compete without a U.S. prime.
The final RFP was released in February 2010 and the program entered source selection on July 9, 2010. The Milestone B Defense Acquisition Board was held on Feb. 23, 2011 and Boeing’s victory was announced the following day. The EMD contract was valued at $4.4 billion with a cap of $4.9 billion, after which Boeing would be responsible for any overages. Boeing reported in its 2020 Q4 earnings that it has paid more than $5 billion in KC-46A related overcharges (see upgrades section for additional details on deficiencies):
- 2014: $425
- 2015: $835
- 2016: $1,128
- 2017: $445
- 2018: $736
- 2019: $148
- 2020: $1,320
Boeing completed the preliminary design review (PDR) in April 2012 and concluded the KC-46 critical design review (CDR) in July 2013. First flight of the 767-2C, an aircraft labeled EMD-1 or VH-001, occurred on Dec. 28, 2014. The first pair of EMD articles (EMD-1 & EMD-2) were built to the 767-2C configuration and were later converted to the KC-46A Pegasus standard. The fourth and final EMD airframe took first flight in April 2016. These aircraft were initially delivered without aerial refueling equipment.
The KC-46A's primary role is air-refueling with a secondary role of transport and aeromedical evacuation. Compared to the KC-135, the new aircraft can deliver more fuel at all ranges; operate from shorter runways; and carry three times as many cargo pallets, twice the number of passengers and over 30% more aeromedical evacuation patients.
The KC-46A is based on the Boeing 767-2C, a derivative of the 767-200ER commercial jet. Retaining the 767-200ER fuselage, the -2C includes a strengthened main deck cargo floor, a cargo door, several freighter features, strengthened 767-300ER wings, 767-400ER horizontal stabilizers, 787-based cockpit displays, auxiliary body tanks for increased fuel capacity and provisioning for the plumbing and extra 50 mi. of wiring required for the refueling mission systems. The aircraft is powered by two Pratt & Whitney PW4062 turbofans producing 62,000 lb. of thrust each and has a maximum takeoff weight of 415,000 lb.
The tanker's refueling equipment will allow it to offload fuel to any fixed-wing aircraft via both boom and probe-and-drogue methods. At its rear centerline, the aircraft carries an advanced version of the KC-10's refueling boom that can offload fuel at 1,200 gallons per minute (GPM). A Center-line Drogue System (CDS) is also installed, which can offload fuel at 400 GPM. In addition, the aircraft is provisioned to carry Wingtip Air Refueling Pods (WARPs), which can also offload fuel at 400 GPM to probe-equipped aircraft. Through this Multi-Point Refueling System, the KC-46 can refuel two aircraft simultaneously from its two WARPs. The KC-46 can carry a total of 212,299 lb. of fuel, of which 207,672 lb. can be offloaded through any of these transfer systems.
The boom, CDS and WARPs are controlled by an Air Refueling Operator System (AROS), located behind the cockpit, rather than at the rear of the aircraft as in earlier tanker designs. The AROS is equipped with two side-by-side control stations, one for an operator and one for an instructor, with independent stick controls. The Remote Vision System (RVS) consists of a 24-in. main display connected to the boom camera and three 15-in. displays above the main display, which together provide a 185-deg. panoramic view.
Located above the refueling system is a cargo deck that can be configured to handle mixed loads of cargo, passengers and patients. The deck can accommodate up to 18 463-L cargo pallets, 58 passengers (or 114 in "contingency" situations) or 58 aeromedical patients (24 litter and 34 ambulatory). The cargo handling system contains seat tracks that accommodates multiple combinations of pallets, passenger seats and patient support pallets. These configurations do not affect the 15 seats for permanent aircrew, including the aerial refueling operator and aerial refueling instructor.
Designed to operate safely in medium-threat environments, the KC-46 hosts a series of self-protection mechanisms. An ALR-69A radar warning receiver alerts the pilots when hostile radars illuminate the aircraft. The AAQ-24 Large Aircraft Infrared Countermeasure (LAIRCM) system combines a two-color IR missile warning system with a directed IR countermeasures set that blinds incoming IR-guided missiles with lasers. A Tactical Situational Awareness System compiles threat information from onboard sensors and friendly aircraft and, when a threat is detected, automatically alerts the crew and suggests a new route. In addition, the cockpit is armored, the fuel tanks have ballistic protection and the entire aircraft is hardened against electromagnetic pulses.
The KC-46 program has been marred by a series of deficiencies which has resulted in delays to production and acceptance of aircraft as well as more than $5 billion in incurred losses for Boeing. The Air Force was originally scheduled to take delivery of its first aircraft in August 2017, but the service would not accept its first aircraft until January 2019 – insisting changes were required prior to delivery. Boeing had 34 KC-46A’s at its Everett facility at varying stages of completion during this period. Under the terms of the contract, the USAF withholds 20% of the payment price for each aircraft until Boeing remedies each Category One issue during EMD.
The government classifies Category One deficiencies as “those that may cause death, severe injury, or severe occupational illness; may cause loss or major damage to a weapon system; critically restrict the combat readiness capabilities of the using organization; or result in a production line stoppage”. Throughout testing, the USAF has identified the following Category One issues:
- Refueling boom extending without command (2017)
- Refueling boom scraping the receiving aircraft (2017)
- Radio antennas generating electrical sparks when transmitting (2017)
- Stiff refueling boom (2018)
- Cargo locking system (2019)
- Leaks with the fuel system (2020)
- Drain tubes with refueling receptacle (to remove water) can crack in low temperature environments (2021)
- Flight Management System produces “navigation anomalies” (2021)
As of June 2021, the stiff refueling boom and RVS constitute the most significant challenges to the program.
Stiff Refueling Boom
According to a May 2021 Defense Department’s Inspector General (IG) report, Boeing changed the off-the-shelf design of the original refueling boom a year after the KC-46 contract award, but the U.S. Air Force’s acquisition office never updated system’s assessed technology risk level.
The 48-page report sheds new light on the causes of a deeply flawed refueling boom that now must be redesigned for $100 million and replaced on all KC-46s that will be delivered through 2023.
“Because the refueling boom was too stiff, it caused pilots of receiver aircraft to inadvertently use excess engine power or not use enough engine power, which, upon disconnecting from the refueling boom, could cause the receiver aircraft to rapidly accelerate toward or away from the tanker,” according to the IG report.
As a result, the Air Force has banned the KC-46 from refueling the A-10 and certain versions of the C-130. Operating restrictions are also imposed on refueling operation for most other types, including the B-52, C-17, F-15, F-16, F-35A, HC/MC-130J, KC-10, KC-46A, and KC-135.
But Boeing’s refueling boom was expected to be one of the lowest-risk items of a seemingly mature platform at contract award. During the KC-X competition, Boeing touted that the KC-46 would use the same refueling boom as the KC-10. Upon contract award in February 2011, the Air Force agreed with Boeing’s description. A mandatory Technology Readiness Assessment identified the refueling boom for the KC-46 as a mature technology, a categorization that exempts the system from more rigorous testing protocols.
A year later, however, Boeing presented refueling boom design changes at the preliminary design review, according to the IG report. The new design included a computer control system. “In contrast, the mature technology of the KC-10 refueling boom—which the KC-46A tanker refueling boom was proposed to be based upon—did not include a computer control system,” the IG report said. But the Air Force never updated the Technology Readiness Assessment for the new boom design with a computer control system. In early 2016, Air Force pilots started noticing problems with the refueling boom. “The boom was too stiff and would not extend or retract during flight testing unless subjected to more force than the system performance specification required,” the IG report said. Boeing tried to resolve the problem with software updates, but it wasn’t enough. The company then added hardware and software updates to fix it. Those changes helped, but the axial loads remained too high for refueling certain aircraft, including the A-10, C-17 and F-16.
The Air Force issued a Category 1 Deficiency Report about the refueling boom in 2018. A year later, the Air Force agreed to pay Boeing to redesign the boom and modify the existing aircraft after the new design becomes available in 2024.
Remote Vision System
Credit: Air Mobility Command
The most enduring problem with the KC-46A has been the RVS. The problem with the RVS is what the Air Force calls a “rubber sheet” effect that distorts the image on the visual display used by the boom operator during refueling operations. The black and white image only images displayed on the baseline RVS 1.0 is are also equivalent to 20/50 visual acuity. These issues make it harder for the boom operator to judge depth perception and distance from the receiving aircraft.
In March 2020, Air Force Chief of Staff Gen. Goldfein testified that while the KC-46 would be used in a high-end contingency – the service will not use them in day-to-day operations until the RVS was fixed. In April 2020, Boeing and the U.S. government have finalized an agreement on a previously undisclosed hardware and software redesign of the KC-46’s RVS. Boeing and the Air Force inked two separate memorandums of agreement – the first on the redesigned vision system, which the service is dubbing RVS 2.0, and the second on releasing $882 million in withheld funds, which was withheld because of the contractor's performance.
Every single facet of the RVS will be altered. The new system will be outfitted with modern, 4K high-definition cameras, with a fiber-optic cable running imagery from the cameras to larger, 4K color displays for the operator, Roper says. “Right now, the cameras are slanted, which creates that warping…We’ll remove that, which will make the image that the operator sees the same as the reality outside of the tanker, so no more warping or rubber sheeting,” he says. Additionally, the new system will incorporate a Lidar laser ranging sensor where the camera box resides. This will paint the receiving aircraft as it approaches the tanker and its boom, providing precision range information to the operator. In January 2022, Aviation Week reported the Preliminary Design Review for RVS 2.0 has been delayed. Testing began in May 2021 and was expected to conclude by the Fall of that year. As of the time of this writing, the Air Force will recommend keeping the PDR open until a fix is fielded to the panoramic display system. The full system is scheduled to field in 2023.
Airborne Battle Management System
The U.S. Air Force has restructured the Advanced Battle Management System (ABMS) program as part of its FY22 budget in a manner that will allow the service to communicate more clearly on Capitol Hill and to deliver new capability regularly – including applications for the KC-46. The Rapid Capabilities Office (RCO) is serving as the integrated program executive officer and selected the KC-46 pod as Capability Release 1. The wing-mounted pod would allow the F-35 and F-22 to pass sensor data back to distant command and control centers, according to Air Force Materiel Command Chief Gen. Arnold Bunch. The RCO is working with specific programs and to release new ABMS increments in a “regular battle rhythm,” Bunch says.
Under the Trump administration, ABMS was one of the service’s top priorities but the fiscal 2022 budget request revealed the Air Force was looking to par down the effort. The service’s fiscal 2022 budget justification documents acknowledge the $204 million better reflects the Air Force’s objectives. The previous year’s budget proposal projected the Air Force would request $449 million for ABMS in fiscal 2022. Congress has been skeptical of the ABMS program and reduced the effort’s budget from $302 million to $158 million in fiscal 2021. The bulk of ABMS funding in fiscal 2022, $147 million, is dedicated to Capability Release 1, while $57 million is for a new digital infrastructure that features secure processing, connectivity and data management.
Production & Delivery History
As of January 2022, Boeing had delivered 52 KC-46As to the USAF (not including the four company operated aircraft). The FY22 budget allocates $2.38 billion for 14 KC-46As, spares and related support. Since the approval of low rate initial production in in August 2016, a total of 94 aircraft have been placed on contract according to the May budget release. The full program of record of 179 aircraft is expected to be procured through 13 production lots through 2027 – with the last aircraft delivering two years later in 2029. The service plans to induct approximately 15 each year throughout the 2020s.
Bridge Tanker KC-Y
The Air Force Life Cycle Management Center issued a sources sought announcement in June 2021 to determine the number of qualified companies that can provide a non-developmental product. “The Air Force is seeking companies that have the capability to deliver approximately 140-160 Commercial Derivative Tanker Aircraft – at a rate of 12 to 15 per year,” the sources sought notice reads. The Air Force is finalizing KC-Y requirements but notes in the sources sought notice that neither stealth nor unmanned capabilities are planned. The service intends to release a final solicitation for KC-Y by the end of 2022 and requires the aircraft to be operational by 2029. The service intends for the KC-Y to bridge gap to the next Advance Air Refueling (AAR) Tanker recapitalization phase, formerly known as KC-Z.
Despite the passage of 15 years, the contenders for KC-Y remain exactly the same. Boeing plans to offer the KC-46. Airbus expects to propose the A330 MRTT, with Lockheed serving as the US-based prime contractor. Over a decade ago, a Republican coalition formed in support of the Alabama-based KC-45 bid. Democrats, meanwhile, generally supported Boeing’s Washington-based KC-46 bid. In 2021, the partisan divide over the Air Force’s tanker acquisition programs has revived on the House Armed Services Committee.
During a June 2021 hearing, three Republican members pressed Air Force leaders to re-open the competition to build the last 77 aircraft of the KC-X program, citing Boeing’s seven-year delay for delivering a fully operational KC-46. “Why are we not bringing this up for a bid?” asked Rep. Jerry Carl, the Republican representative of a district that includes Mobile, Alabama, the home of an Airbus narrowbody aircraft manufacturing center. Rep. Rob Wittman, a Republican who represents a Virginia district that borders the site of the Airbus Americas headquarters, agreed, saying: “I think the [current] program is irreparable and the underlying cause is a bad contract.” A Democrat, however, challenged the Republicans’ arguments during the hearing. Rep. Donald Norcross, who represents a New Jersey district that lies directly across the Delaware River from a Boeing helicopter plant, said the Republicans are holding the KC-46 to a higher standard than any other weapon system.
Meanwhile, the Air Force’s refueling needs are growing. In 2019, the Air Force assessed that its existing tanker fleet could support only half of the training sorties scheduled by the service’s major commands. That demand could draw scrutiny over the different sizes of the candidates. In 2011, Airbus offered the A330 MRTT with 20% more fuel capacity than the KC-767. Despite the MRTT’s larger fuel capacity, interoperability with major U.S. allies and industrial benefits, introducing a new type into the inventory would entail a host of training, manning and logistics support costs the service would likely be keen to avoid.
The Japan Air Self Defense Force (JASDF) ordered four KC-767 tankers from Boeing which were delivered between 2008 and 2010. In October 2015, Japan became the first foreign military sale (FMS) customer of the KC-46 program. In Sept. 2016, the DSCA issued a notification regarding the potential sale of six KC-46As as well as associated equipment and support services for an estimated $1.9 billion. In September 2019, Boeing began manufacturing of the JASDF’s first KC-46. The fleet is expected to be based at Miho Air Base in Tottori Prefecture and will supplement the JASDF’s existing KC-767s.
In June 2021, the Air Force announced it had recently begun training JASDF KC-46 pilots at Altus Air Force Base, Oklahoma. A total of six pilots and six boom operators will participate in the first three month course. The JADSF took delivery of its first aircraft in January 2022.
The US State Department approved a pending sale of eight Boeing KC-46 tankers to Israel on March 3, 2020. The export package includes eight KC-46s and 17 Pratt & Whitney PW4062 engines, which includes a spare propulsion system. Raytheon also would supply 18 GPS receivers, with an anti-jam and spoofing capability. The entire package, including logistics and training support, is worth $2.4 billion. In February 2021, Israel signed a Letter of Offer and Acceptance (LoA) for its first pair of KC-46s. Jerusalem signed an LoA covering an additional pair of aircraft on Dec. 30, 2021. Deliveries are expected to begin in 2025.