Once again, we are honored to have a timely guest post from Mr. Bustamante with his thoughts on Navy tanker aircraft needs. Please be sure to read his bio at the end of the post.
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Why the Navy Needs a
Really Large Tanker Aircraft
Some Unruly
Thoughts on Strike Warfare Against a Peer Competitor [1]
Figure 1. S-3Bs Conduct Aerial Refueling with
the Hose-and-Drogue System
If the
U.S. Navy expects to employ carriers against peer competitor who can establish
substantial Anti-Access and Area Denial (A2/AD) defenses, it will need large
tankers, much longer ranged tactical aircraft, and long-ranged standoff weapons. The Center for Strategic and Budgetary
Assessments has published several excellent analyses papers making the case
that we face adversaries with A2/AD defenses designed specifically to counter
American naval and air-superiority extending from 1,000 nm, to1,500 nm or more from a hostile coast.[2] It is important to note that ships,
submarines, aircraft are not automatically destroyed when they enter into an
area protected by a sophisticated A2/AD network, but they do risk detection and
ultimately destruction that is directly related to the time exposed to the
enemy maritime strike-reconnaissance network.
This presents a formidable range requirement for naval aircraft designs
built in the last four decades and one that seems unlikely to be met
satisfactorily with external fuel systems like conformal fuel tanks.[3] Ironically, a typical 1960s carrier task
force had both long ranged attack aircraft (A-3s, A-6s, and A-5s), and the
tanker assets necessary to support escorting fighters for long range strike
missions.[4] The USN today, however, finds itself without
long ranged aircraft due to decades of aircraft procurement policy favoring
sortie generation over “deck load strike”, failure of the A-12 program, and
retirement of long-ranged legacy aircraft.
The requirement for a long range attack aircraft and a big tanker is
driven by the physics of fuel consumption and the relatively short range of
carrier aviation. Tanker aircraft allow
strike packages to launch with maximum weapons load, but minimum fuel loads, then
aerial refuel to maximize fuel load, while simultaneously reducing stress on
airframes and extending the life of aircraft.
Large tankers are not only more efficient at delivering fuel, they are
also a welcome savior for aircraft returning with combat damage, or Combat Air
Patrol (CAP) aircraft returning from an extended mission. While the F/A-18 is criticized for its
relatively short combat radius, the reality is that the longest ranged carrier-based
fighters would be challenged by today’s A2/AD defenses.[5] The current solution to this dilemma is
provided by U.S. Air Force, which operates the core of U.S. military aerial refueling fleet, largely consisting
of ~460 KC-135 and KC-10 aircraft.[6] These aircraft have performed yeoman service
for naval aviation, but the USAF tanker fleet is prioritized for USAF
requirements: delivery of large volumes of fuel to a single large bomber. USAF tankers are primarily configured to use a
unique “flying boom” fuel delivery system, a rigid, telescoping tube that the
tanker aircraft extends and inserts into a receptacle on the aircraft being
refueled; however, Navy and Marine Corps aircraft refuel using the “hose-and
drogue” system, which is a flexible hose that trails from the tanker and drogue
(windsock) that stabilizes it in flight.[7] The USAF also uses JP-8 fuel, while the Navy
uses JP-5. In order to fuel USN and USMC
aircraft, Air Force tankers generally have to flush their tanks and install a modified
hose-and-drogue system, the inventory of which is sufficient to equip about a
third of the tanker fleet.[8] The new KC-46A is equipped with both the
flying boom and the hose-and-drogue systems built into the airframe, but aircraft
fuel compatibility remains an issue.
Figure 2. USAF
KC-135A Refueling a B-52D1
1. The flying boom
system designed specifically for fast, efficient refueling of very large
aircraft like bombers.
The KC-46A
is also just entering production and the current procurement plan is for only
179 aircraft.[9] The balance of the USAF tanker fleet is also
old and shrinking.[10] Moreover, the USAF is likely to need every tanker
to support a long-range bomber campaign in a high end conflict and these
aircraft will be based to support USAF missions. This is likely to leave Navy aviation without
desperately needed aerial refueling capability in war. This article will first examine the long
range strike mission, review the aerial refueling requirements needed to
support strike packages, and then show why current naval aircraft are not well
suited the role. Finally we will suggest
some solutions to the issue.
Figure 3. USAF
KC-46A Refueling a Pair of F/A-18s1
1. The KC-46A has
both the flying boom system; and the hose-and-drogue system.
We
should ask ourselves, does the USN have a requirement to conduct long range
strike operations using carrier based aviation?
Dollars are tight - a large tanker, and possibly a large tactical
aircraft program, must fully justify the additional expense. We could accept the status quo where
long-ranged naval strike missions are tied to the availability of USAF tanker
assets. After all, the USN, and USMC
used USAF tankers to support long missions to Afghanistan following 9/11.
Besides, the USAF is tasked with deep inland strikes; the USN has plenty
of RGM/UGM-109 Tomahawk missiles for long-range strikes and highly capable submarines
for clandestine launches. Finally, there
is the argument that carrier aviation exists to provide local air superiority
for naval task forces – thus an alternate strategy for carrier employment might
call for blockade, minelaying, and commerce raiding instead of deep strike. In the end, none of these propositions are
entirely acceptable; particularly given that the Navy had a plethora of tankers and long-range attack aircraft in the
middle of the last century. This is a
problem with a readily definable technical solution that was worked out in the 1950s and then fielded. Large organic tanker capability is incredibly
useful, even when conducting strikes well within the range of strike aircraft. USAF tankers are not always going to be
conveniently based to support naval strikes, especially if the Navy pursues
operations outside the USAF’s primary theater of operations. In practice, USAF aircraft flying from known,
geographically fixed bases may prove to be more vulnerable to attack than an
aircraft carrier. The submarine launched
deep strike mission is in direct competition with the use of submarines for the
critical anti-submarine warfare (ASW) mission and the commerce raiding
missions, which I give much higher priority.
Further, an operational shift, or technological breakthrough favoring
ASW might dramatically affect submarine survivability or effectiveness. Finally, a good military policy is to retain redundancy
and flexibility with weapon systems and units where possible.
Modern
tactical air operations place a premium on Suppression of Enemy Air Defenses
(SEAD); the ratio of aircraft actually delivering steel on target might only be
one out every three or four planes. Most
of the aircraft in a strike package will be fighter escorts, electronic warfare
aircraft, SEAD aircraft, command and control aircraft, and other air frames, just
to make sure the bomb droppers get to their weapon release points.[11] During the Gulf War, strike packages of
up to 50-60 tactical aircraft were generally required to assure the penetration
of 12-16 aircraft with ground attack munitions!
The proliferation of advanced SAMs and advanced fighter aircraft gives
us little hope that the situation will dramatically improve. Additional considerations are the extensive
fortifications constructed by many potential adversaries to protect key
military and civil infrastructure to complicate U.S. strike operations.
This will demand larger ordinance loads, and also gives us little hope
of using external fuel tanks extensively as a solution to extending aircraft
range.
So
what would it take to support the fuel needs of a carrier task force (TF) strike
package of 60 or so aircraft? I am
assuming the TF is willing to risk a high speed dash at 30 knots to penetrate
240 nm into the A2/AD network (~8hrs), and that stand-off weapons range is 60+
nm, so the strike package needs to penetrate (fly) about 900 nm get to weapons
release point for stand- off weapons The
key determinants are based upon the combat radius and fuel capacity of the
aircraft flying in the strike. Table 1
below gives us a quick summary of open source data in very rough approximation
of the fuel and combat radius characteristics of selected naval aircraft. Aside from the F/A-18E and F-35C, several
historical aircraft are included as “place holders” to approximate potential
performance of future aircraft.
Table 1. Fuel
and Combat Radius Data for Tactical Naval Aircraft
Source: open source data is approximate and are for
illustrative purposes.
1. Combat radius is a
very complex and qualified figure, see end note 2.
2. F-35C figures are yet to be demonstrated.
The
F-111 was included in the table because it was originally intended to be a
joint USAF/USN carrier capable design and approaches the maximum size and
weight of carrier capable airframes like the A-3D Skywarrior and A-5 Vigilante,
arguably the closest aircraft to a strategic bomber that the USN has produced.[12] The take away is that naval aviation, now
based upon the F/A-18, is short ranged, and hugely dependent upon aerial
tanking to conduct very long range strikes.
Even the “long-ranged” F-14 has qualifications. A very rough estimate for an alpha strike
package of 60 F/A-18 aircraft (to include F/A-18Gs) will require at least 36,750
lbs. of fuel, and three refueling operations per aircraft to reach 900 nm. A strike package of 60 aircraft would require
over 2.2 million lbs. of fuel! This
figure could overstate the actual fuel requirement because long-range missions
may allow aircraft to operate at speed/altitude profiles that significantly
enhance their fuel efficiency. On the
other hand, commonly quoted combat radii, do not address the inevitable delays
that occur when aerially refueling dozens of tactical aircraft. Also note, that this mission also requires
tankers operate at least 600 nm from the carrier. The situation improves slightly for an all F-35C
strike package (27,990 lbs. per aircraft, 1.7 million lbs. of fuel for a 60
aircraft formation – but it still is a formidable requirement. It is also questionable if the USN will buy a
sufficient number of F-35s, and even if it does, the only tactical jammer currently
in the U.S. inventory is the F/A-18G. The F-35 is supposed to deliver many
capabilities that promise to reduce the size of strike packages and increase
survivability, but these have yet to be demonstrated. A partial solution is of course to use
external fuel tanks, but these come at a performance penalty and also increase
the detectability of the strike force. For
these reasons, and to simplify what can be a very complicated analysis, the
strike package fuel requirement assumes internal fuel loads only.
Having
stated the requirement, what tanker assets are available to support the strike
tanking requirements? Table 2 below
provides a summary of selected aerial refueling aircraft in the U.S. arsenal and matches them to the number of tankers
required to deliver 1.7 million pounds of fuel to support a 60 aircraft strike.
Table 2. Summary
of Selected U.S. Aerial
Refueling Assets
Source: open source data; approximations are for
illustrative purposes.
1. Note that with the exception of the KC-135, all of the other aircraft options fail to provide fuel at useful ranges.
2. Figures are rounded up to the nearest whole number of aircraft.
3. The more common EKA-3B could deliver 21,000 lbs. of fuel at 460 nm, enough to fuel 2.2 full F-4Js, but it also retained significant stand-off jamming capabilities and could still carry ordinance while operating as a tanker. The KA-3 and EKA-3B were far and away the best aerial refueling assets the Navy built. They were also the largest carrier capable aircraft ever built with about 82,000 pounds maximum take-off weight.
4. With two 300 gallon tanks.
5. The KS-3A program was cancelled afte a single prototype was built. Had it entered production,it arguably might have been the most capable dedicated Navy tanker.
6. The F/A-18E configured as a "buddy tanker".
What
Table 2 really demonstrates is the huge load efficiency of very large,
land-based tankers with maximum take-off weights exceeding 320,000 lbs. (the
KC-46A has a maximum take-off weight of 415,000 pounds - over five times heavier
than the largest carrier aircraft ever deployed, the KA-3). This analysis also underestimates the tanking requirements of a long range strike
package because with the exception of the KC-135, all of the other aircraft options fail the ability to provide fuel at
useful range. It also shows that the
best tanker the Navy ever acquired, the KA-3, was still inefficient as a
tanker, requiring an almost one to one ratio of tankers to F-35Cs to support a
900 nm strike. The very worst tanker
option is the F/A-18E operating as a “buddy tanker” due to the short intrinsic
short range of the airframe. In fact,
the F/A-18E “buddy tanker” configuration will burn most of its transfer fuel capacity to reach 600 nm.
Figure 4. The
Navy’s Best Tanker Ever - an EKA-3B Skywarrior Refuels an F-14
Source: A-3 Skywarrior Association
This
is reminiscent of the U.S. Army Air Corps fiasco in WWII called Operation
Matterhorn: an ill-conceived strategic bombing campaign against Japan by basing B-29s bombers in India and staging them from airfields in China. Every gallon
of fuel, every pound of ammunition and other military supplies had to be flown over
the Himalayas to China. Because the
B-29 was inefficient as a tanker, it took
seven round trip B-29 flights to build up enough fuel for a single B -29 mission
against Japan; prompting General Curtis E. LeMay the commander of XX bomber
Command to say: “The scheme of operations had been dreamed up like something
out of ‘The Wizard of Oz,’ ...”[13] Carrier aviation, lacking both a large
tanker, and long ranged aircraft, is in danger of repeating this error.
Matching
requirements to assets, suggests a number of options the U.S. Navy can, and
should take to improve its strike capacity against first class adversaries with
advanced A2/AD defenses. Specifically:
1) In the short term, the Navy should study the
feasibility of returning some of the 100 A-6E aircraft in storage to service after
refurbishment and conversion into KA-6Es.
The A-6E was given new composite wings shortly before retirement and
could provide a great deal of relief to the air wings. Conversion to unmanned or optionally manned operation
should be considered.
2) Long term, the Navy needs to procure a very large,
carrier capable tanker aircraft with a maximum take-off weight of 80,000 pounds
or larger, and an objective transfer
fuel load of 40,000 lbs. delivered to 600 nm.
This aircraft should follow the “payload over platforms” design
philosophy and provide a robust “pick-up truck” functionality over stealth and
other features.
a) The aircraft could be unmanned or optionally manned.
b) A flying wing or blended wing design seems
appropriate to maximize lift and internal fuel capacity.
c) The tanker should have several "joint"
features for maximum compatibility with the USAF and allies that use the flying
boom (e.g. Australia):
i)
Incorporate a
flying boom receptacle to enable the new tanker to receive fuel very quickly
from USAF tankers, while simultaneously refueling USN aircraft.[14] This would open a number of tactical
advantages, shorten refueling times, and allow strategic tanker aircraft to
complete their missions more rapidly.
ii) Incorporate certain USAF mounts for large capacity
external fuel tanks.
iii) Possibly incorporate a flying boom for refueling USAF
fighters.
3) From a joint perspective, the Navy and Air Force must
continue to integrate operations and ensure equipment interoperability.
a) The U.S. military needs to move to a single aviation fuel
type to minimize logistics issues. Given
the number of aircraft in each service, this means that the Navy and Marine
Corps should adapt JP-8, which is similar in chemical composition, but has a
lower flashpoint than JP-5.
b) The Navy must also seriously consider incorporating
the USAF flying boom/receptacle compatible system into large aircraft like the
P-8 or future attack aircraft. It also
means that the USAF must maintain sufficient numbers of Wing Air Refueling Pods
for legacy tankers to support naval aircraft.
This is key, the Navy must support the USAF 100% in obtaining funding
for these pods.
4) Future naval aircraft must place a much higher
emphasis on range and payload than the past three decades. Plainly stated, this requirement greatly
favors a large, long-ranged heavy attack aircraft; the same physics of moving
large bomb loads over great distance was exactly what drove the procurement of
the A-3, the A-6, and the A-5. This
aircraft will need to be larger than the X-47B - it could also be a drone or
optionally manned. It should incorporate
certain USAF mounts for large stand-off weapons and large capacity external
fuel tanks.
5) Improve stand-off ranges with a very long ranged
(1,200 to 1,500 nm) air to ground weapon.
This also favors a large heavy attack aircraft in A-3/A-5/F-111weight
class. Consider:
a) Adapting Navy aircraft to carry long ranged USAF air-to-ground
cruise missiles with conventional warheads to support strike operations. This implies a large attack aircraft to carry
them: for example an AGM-129A missile weighs over 3,500 pounds.[15]
b) Procure a long ranged air-to-ground ballistic missile
with a conventional warhead to support strike operations.[16]
These are appropriate
actions for naval aviation but the Navy in general needs additional reforms to conduct
strike warfare against modern a2/AD defenses.
First and foremost is the procurement of a very long ranged (1,200 to
1,500 nm) ship launched cruise missile and/or ballistic missiles for strike
operations. These weapons need not only
greater range than BGM-109 tomahawk, they require more sophisticated warheads,
for example anti-radiation seeker heads, earth penetrating warheads, and EW
packages like jammers. Serious
consideration to stealth and hyper velocity propulsion is essential.
[1] This article addresses high end war against a peer
competitor, not COIN operations.
[3] The details of combat radius are highly technical
and dependent upon a number of factors (ordinance and fuel loads, ingress and
egress altitude, dash speed, weapon drag, etc.), but typical tactical aircraft
combat radii range from 350 nm to about 600 nm.
External fuel systems work well, but impose trade-offs in performance,
particularly in maneuverability, radar cross section, and use, or interfere
with, munition hard points.
[4] This capability was developed because Admirals
Mitscher and Sallada proposed a nuclear bomb capable attack bomber in 1945 with
a 1,000 nm combat radius leading directly to the A-3 Skywarrior and later the
A-5 Vigilante. U.S. Aircraft Carriers,
An Illustrated Design History, by Dr. Norman Friedman, 1983, pages 240 and 241.
[5] The F/A-18 does what it was designed to do, the
problem is the carrier air wing lost the supporting cast of aircraft types.
[6] Formal Joint air refueling operations between the
Air Force and Navy started in the early 1970s.
A 1988 memorandum of understanding (MOU) established joint air
-refueling concepts.
[7] Congressional Research Service report RL32910, Air
Force Aerial Refueling Methods:
Flying Boom versus Hose-and-Drogue, by Christopher Bolkcom pages 2 and 3, June 5, 2006.
[8] The KC-10 is configured to allow the alternate
simultaneous use of either the flying boom or the hose and drogue if equipped
with Wing Air Refueling Pods (WARP).
This does not solve the issue of the services using different fuel
types. Only about one out of every three
USAF KC-10s had Wing Air Refueling Pods (WARP), and these are low priority
procurement items for the USAF. Naval Air Refueling Needs Deferred in Air
Force Tanker Plan by Hunter C. Keeter, Sea Power magazine, April 2004.
[9]
http://www.af.mil/AboutUs/FactSheets/Display/tabid/224/Article/104537/kc-46a-tanker.aspx
[10] GAO found that the average age of the KC-135 fleet
was 35 years back in 2003. GAO-03-938T,
page 4.
[11] A combat grouping of aircraft with different
capabilities that are launched together to perform a single attack mission
[12] The C-130 is the largest aircraft to land and take
off from aircraft carriers. In October
and November 1963, a KC-130F (BuNo 149798) made 21 landings and take-offs on
the USS Forrestal. It is important to
note that the C-130 essentially shut down normal flight deck operations and was
(remains) unsuitable for normal carrier operations.
[13] The Matterhorn
Missions, by John Correll, pages 62-65, AIR FORCE Magazine, March
2009. http://www.airforcemag.com/MagazineArchive/Documents/2009/March%202009/0309matterhorn.pdf
[14] Designed properly, a USN tanker could receive fuel
from a USAF tanker via the boom, while also fueling two Navy aircraft. In the case of a KC-10, or KC-46A, the possibility
of fueling the Navy tanker (via the flying boom) and four tactical aircraft via
hose and reel (two from the USN tanker, and two from the USAF tanker, is a
possibility.
[16] The Douglas AGM-48 Skybolt Air-Launched Ballistic
Missile from the 1950s suggests one possible weapon. It was very heavy weighing
almost 11,000 pounds.
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Mr. Bustamante is a retired naval officer who served the majority of his career as a Naval Special Warfare Officer, but also as a Surface Warfare Officer and Foreign Area Officer. He is a graduate of the U.S. Naval Academy with a degree in Systems Engineering. He also holds a Master of Science degree in Defense Analysis (Operations Research) from the Naval Postgraduate School in Monterey, California. After retiring from the Navy, Mr. Bustamante worked for the legislative branch as an auditor and analyst, as a civil servant with the United States Department of State, and also in the private sector as an analyst in information technology project management.