Air Mobility Command’s Future Tanker Problem

By: Andrew P. Hardy
Approximate Reading Time: 11 Minutes

Excerpt:  The Department of Defense (DoD) faces a significant crisis in its power projection capability. The ability to execute missions in an anti-access/area denial (A2/AD) environment needs to be reevaluated in terms of air-to-air refueling (AAR). This analysis examines Air Mobility Command’s (AMC) future tanker problem in light of current plans for the future tanker fleet, by considering the boom versus drogue problem, as well as the dilemma posed by the adaptive basing concept. Ultimately, this analysis proposes the need for three different types of tanker aircraft to operate in future conflicts.

The DoD faces a significant crisis in its power projection capability in terms of its utilization of fifth-generation fighters in near-peer adversary conflicts. In order for the United States (US) to remain effective against China and Russia’s A2/AD strategies, the DoD’s ability to execute penetrating, long-range strike missions should be reevaluated in terms of AAR. The United States Air Force (USAF) and United States Navy (USN) have fifth-generation fighters with short combat radiuses that are unable to be supported by AMC’s current tanker force in A2/AD environments without facing undue risk. With the proposed cut to the KC-Y program, the DoD faces an unbalanced AAR force unable to meet the needs of the USAF, USN, and US allies with respect to a potential future near-peer conflict.

The US campaigns in Iraq and Kosovo in the 1990s showed the world that wars can be waged effectively over short distances from airfields and carriers. However, the US did not take into account that adversaries would adapt. China and Russia learned at least two distinct lessons from observations during the 1990s. The first lesson regarded the surprising effectiveness of strikes against Iraq’s surveillance and command and control networks with stealth aircraft like the F-117. The second lesson was that Iraq made a huge mistake allowing the US to build up forces in Saudi Arabia without resistance. These lessons provided the foundation for advanced radars and missiles that makeup the A2/AD network infrastructure that we see in China and Russia today. To counter this, the DoD invested in stealth aircraft like the F-22 and F-35, which have become the lynchpin for 21st century USAF strategy. Conventional fighters like the F-16 and F/A-18 can carry fuel in underwing tanks, whereas stealth fighters cannot carry external fuel stores while maintaining their stealth radar cross-section parameters. To maintain a modernized tanker force, the USAF has proposed three future tanker concepts: KC-X, KC-Y, and KC-Z.

The Current and Future Tanker Fleet
AMC’s current fleet of tankers is comprised of the KC-135 Stratotanker, KC-10 Extender, and the KC-46 Pegasus. All of these aircraft stem from an original commercial aircraft design (the Boeing 720, McDonnell Douglas DC-10, and Boeing 767 respectively). The KC-135s have proven themselves since the Vietnam War but are showing their age in terms of maintenance, a lack of defensive systems, and limited situational awareness. The KC-10s excel in multiple large offloads and are ideal for coronets (which allow fighters to traverse long distances continuously), but like the KC-135s, they have no defensive systems with even less situational awareness. Finally, the KC-46 was chosen for the KC-X requirement. KC-46 deliveries are currently delayed and it is anticipated to be approximately three years away from full operational readiness as a result of delays with the boom visual curing system as well as the boom design. Nonetheless, the KC-46 will be modern in terms of defensive systems and situational awareness.

AMC Tanker Specs KC-135 KC-10 KC-46
Date Deployed 1956 1981 Delayed
Max Takeoff Weight 322,500 lbs. 590,000 lbs. 415,000 lbs.
Max Fuel Load 200,000 lbs. 356,000 lbs. 212,299 lbs.
Max Cargo Capacity 83,000 lbs. 170,000 lbs. 65,000 lbs.
Pallet Positions 6 27 18
Fuel used per hour 10,000 lbs. 18,000 lbs. 12,000 lbs.
Boom / Drogue / Both Boom or Drogue / Limited MPRS aircraft Both / Additional Drogue with WARPs Both / Additional Drogue with WARPs
Crew 3 4 3
Unit Cost $52 million $88.4 million $147.4 million
Threat Environment Low Low Medium
Inventory 396 59 7 today / 179 expected

The KC-Y and KC-Z programs were designed to modernize the legacy tanker fleet. The KC-Y is intended to recapitalize the remaining KC-135s and be ready by 2028. Some AMC leaders have suggested, however, that the KC-Y competition may be scrapped in order to save time and money by avoiding a new contest. Instead, some would prefer to simply expand the purchase of KC-46s to promote fleet commonality. The KC-Z was originally intended to recapitalize the KC-10 fleet in the late 2030s. The USAF’s top acquisition official says that the KC-Z will likely be unmanned but many concepts are still being finalized. Specifications such as decreased radar and infrared signatures, advanced electronic warfare systems, and a hard-kill, anti-missile system are being looked at to balance survivability and stealth for the future platform. Rumors even go as far as turning a Northrup Grumman B-2 into a tanker or using the future B-21 Raider as the basis for a KB-21 aerial refueler.

The Boom vs. Drogue Problem
Along with the KC-X, KC-Y, and KC-Z programs, AMC faces a future fuel transfer problem in regards to stealth. The USAF uses a boom type of transfer system to allow faster offload rates equating to more fuel available in shorter periods of time for receiver aircraft. The USN along with US allies, have chosen the drogue type of transfer system due to a more simplified transfer process (requiring less engineering and personnel involvement) despite slower offload times.


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KC-46A Boom Receptacle
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KC-135 Drogue Refueling an F/A-18

Compared to boom refueling, drogue refueling takes two to four times longer to offload the same amount of fuel depending on the receiver aircraft and tanker equipment. This presents a complicated problem for the USAF, especially when looking at an unmanned and stealthy next-generation tanker. In Fiscal Year 2020, according to the latest budget request, the USAF will begin design work on a small, pod-mounted tactical air refueling boom for mobility operations. Building a boom that will fit in a pod while remaining stealthy will be a significant challenge. Past tests have successfully demonstrated that a drone can refuel via boom from a manned tanker, but the test and evaluations community has yet to demonstrate the reverse. Delicate and precise movement is key to the tanker aircraft especially when the stealth characteristics could be compromised if a scrape occurs on the receiver aircraft. Currently, the MQ-25 Stingray– formally the Unmanned Carrier Aviation Air System (UCASS) – is the Navy’s response to carrier-based aircraft range limitations in A2/AD environments. Unmanned tankers are a dramatic shift in the way combat requirements are defined. By incorporating an already proven design, the capability provided by AMC could help level the A2/AD environment playing field.

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Lockheed Martin’s MQ-25

The USAF’s Adaptive Basing Concept
The USAF has operated out of established bases for decades, making these locations predictable targets for adversary surface-to-surface and air-to-surface missiles. Part of the DoD’s answer to the A2/AD strategy from both China and Russia is the adaptive basing concept. This idea centers around rapidly refueling and rearming aircraft in an austere environment to complicate and confuse an adversary’s Command, Control, Communications, Computer, Intelligence, Surveillance, and Reconnaissance (C4ISR) capabilities. Large tanker aircraft will still make easy targets and will remain under constant missile threat, which will hinder crew rest and decrease dependability of AAR efforts. In order for adaptive basing to be effective, AMC’s tanker layout will need to be modified. The USAF needs three different types of tanker aircraft to operate in future conflicts: 1) an AAR and cargo capable KC-135 replacement tanker, 2) a special purpose unmanned stealth tanker, and 3) an AAR devoted KC-10 replacement stealth tanker.

The Proposed Future AMC Tanker Force
The KC-46 was chosen to fulfill the KC-X requirement to replace the KC-135 and serve as the backbone of AMC’s AAR fleet. It will be able to support both boom and drogue requirements without a configuration change like the KC-135 (minus MPRS), possess significant cargo capability, modern defensive systems, and C4ISR connectivity all while operating in medium threat environments across the globe. The KC-46 should also be the only cargo capable tanker in AMC’s inventory due to specialty requirements for A2/AD environments. I believe that the KC-46 is the right choice for AMC and will fill some critical risk and communication gaps. However, the KC-46 will be significantly limited in A2/AD environments, exposing crews to high-risk in a near-peer fight, and therefore is not the sole answer to AMC’s AAR future.

The potential scrapping of the KC-Y competition will introduce a significant detriment to the AAR capability of the USAF and the DoD’s ability to project power. AMC needs to provide a tanker that can operate in an adaptive basing construct while being realistic with manned crew limitations. This tanker will not have a cargo mission due to its smaller size requirement. The Navy’s MQ-25 Stingray needs to be expanded to provide further range in offload capability where size is not a limitation as it is on an aircraft carrier. Using the same basic blueprint, the USAF can develop a larger platform that can launch and recover remotely from various austere environments. Further launch ideas could include commercial roads where these unmanned aircraft could be deployed from semi-trailers to blend in with civilian transport and complicate adversary C4ISR efforts. Boom and drogue configurations would need to be developed to support USAF aircraft as well as USN and allied fourth and fifth-generation fighters.

Without the KC-Z aircraft having similar capabilities as the KC-10, AMC will see significant impacts to offload capability, flexibility, and significant complications with coronet efforts. The main advantages of the KC-10 are the multiple large offloads available to receivers as well as the range required for fighter drags. Roughly double the KC-135s/KC-46s are needed to support the same requirements that a single KC-10 can fulfill. This type of capability is critical in supporting bomber standoff weapons requirements for an A2/AD network breakdown in terms of pre-vul and post-vul fuel requirements. This new aircraft will use a non-commercial stealth shape to limit radar cross-section and focus on maximum fuel capacity. To help save costs, the entire fleet will not require radar absorbent materials (RAMs) like other stealth fighters. Eighty percent of stealth comes down to shape and the RAM can be included on a limited number of specialty tankers if that requirement is deemed necessary. Not having to worry about RAM coating on a large airframe will provide significant savings on training and maintenance costs. Lastly, the KC-Z will likely be unable to fulfill a cargo requirement like the KC-10 based on its stealth shape. AMC will need to adjust and utilize its mobility force to fulfill cargo requirements necessary for coronet packages.

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Lockheed Martin’s KC-Z Concept


The US emergence as the sole superpower after the collapse of the Soviet Union, combined with over 18 years of fighting the war on terror, has delayed the modernization needed for an effective future tanker force. The KC-135 and KC-10 have provided a critical warfighting capability that needs to be continued and modernized for the 21st century. The potential elimination of the KC-Y will create a critical gap in tanker capability for AMC. The KC-Z could face unrealistic expectations in becoming a “jack of all trades” aircraft which would undermine its potential. AMC needs three different types of tanker aircraft to operate in future conflicts: 1) the KC-46 that will replace the role of the KC-135 and serve in a wide variety of medium threat conflicts, 2) a stealthy unmanned aircraft similar to the MQ-25 Stingray that will be able to provide fuel in high-threat A2/AD environments to fifth and sixth-generation fighters, and 3) a KC-10 replacement that can support large fuel requirements while having a stealth radar cross-section and the potential to operate unmanned. AMC needs to be open to unmanned aircraft in its fleet and should remove the cargo requirement for every aerial refueling platform. The USAF needs to capitalize on the research and design of the MQ-25 Stingray as well as the B-21 Raider as potential models for the KC-Y and KC-Z in a time of recapitalization. The short range of today’s fifth-generation fighters will not be effective unless the future tanker force is correct. AMC’s future tanker problem could jeopardize future USAF mission effectiveness if it is not intelligently modernized to be able to support emerging fighter and bomber aircraft operating in the A2/AD environment. The DoD needs to recognize the USAF’s future tanker vulnerabilities now, and allocate sufficient funding to emphasize to Russia and China that their A2/AD networks are not impenetrable.

Maj Andrew “RATCHET” Hardy is an Evaluator Pilot with over 2,600 flight hours and 245 combat missions in the KC-135 R/T/RT. He is a graduate of the United States Air Force Weapons School and a student at Air Command and Staff College in the Multi Domain Operational Strategist program. Email:

The views expressed are those of the author and do not necessarily reflect the official policy or position of the Department of the Air Force or the US Government.

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2 thoughts on “Air Mobility Command’s Future Tanker Problem

  • April 18, 2019 at 3:43 am

    Nice write up Ratchet. Especially like the use of KC-Y iso Adaptive. The small payload pays off if it can get close or fly repetitively. The shuttle-tanker concepts I’ve seen are less compelling.

  • July 13, 2019 at 3:06 am

    this article addresses the wrong A2/AD challenge problem. USAF can contribute a solution, but this would require substantial doctrinal innovation, and some pilot operating risk while working more closely with the USN & US Army Corps of Engineers.


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