Rethinking the High-Low Mix, Part II: Complexity’s Death Spiral


Editor’s Note: Please read part one of this series, “Origins Story.”

When you find yourself at the bottom of a hole, stop digging — especially when you will need a century (or two) of hard work to scramble out of it. This bit of wisdom is likely what the commander of Air Combat Command, Gen. Mike “Mobile” Holmes, had in mind when he once described the regretful state of the effort to modernize the service’s combat aircraft fleet:

Since Desert Storm, we’ve been on a recapitalization schedule of somewhere between 100 and 200 years, if you’d see how many airplanes we’ve been [through] and the size of the total fleet. If we can get to 48 F-35s a year, that would put us on a 40 year recapitalization schedule. So we’ve got to find a way to acquire more airplanes. We’ve got to work to make the airplanes we’re acquiring affordable, and then we have to make sure we’re getting the right things for the CAF [combat air force] too.

If this were the movie Jaws, it would be the equivalent of the unheeded revelation that “we’re going to need a bigger boat.”

In the first installment, we discussed what is known in the defense aircraft industry as the “high-low mix.” The idea, put forward in the 1970s by a group known as “the reformers,” embodied the notion that a small number of highly complex aircraft should be augmented by a larger number of less-complex assets. One would be forgiven for jumping directly to the conclusion that this is purely a function of economics: If we cannot afford to go “all-high,” we should fill out the ranks with lots of low-cost, easy-to-build aircraft. However, before making that leap, it is helpful to understand the vector by which complexity infects an aircraft program. If complexity is the disease, then high cost, low production rates, low readiness, and low adaptability are the symptoms.

In aeronautics, there is a high penalty for trying to do too many things well in one vehicle — physics is a harsh master. There are great lengths involved in achieving robust performance spanning several metrics. When the combination of maneuverability, stealth, speed, generous payload capacity, and long range are all included in one platform, it inevitably leads to the development of a highly complex aircraft. Throw in a plethora of exquisite sensors and a few million lines of code to make everything work together, and you are well on the way to eye-watering complexity.

However, by following a disciplined approach about which technologies to incorporate, there is hope yet for recapitalizing to a more capable, adaptable, and affordable combat fleet. This approach requires adopting the effects-based view that several simple, focused-performance aircraft can aggregate to a robust multi-role capability that a single highly complex tactical platform can never achieve.

Lost in Translation

Contrary to the reformers’ intentions for  the high-low mix, “high” and “low” have become adjectives to describe attributes other than the complexity of the aircraft in question. Often, “high” and “low” are incorrectly applied to the cost of the aircraft or its expected mission. While it is true that low-complexity aircraft may be appropriate for combat in permissive airspace, it ignores the more salient question of whether certain types of low-complexity, focused designs might be useful in denied or contested airspace. By inadvertently steering the conversation away from complexity, we are forgetting the disease.

Since the introduction of the “high-low mix” concept nearly 40 years ago, very few aircraft programs can be easily categorized as being on the “low end” of the spectrum. The impetus of the F-16 program provides the stand-out example, but even that simple fighter aircraft morphed over time. In the 1970s, the U.S. Air Force viewed the F-16 as a low-end aircraft to augment the F-15C air superiority fighter. Yet the F-16’s contribution to the multinational fighter program saw many NATO countries acquiring the aircraft to replace aging F-104 Starfighters, thereby anchoring the high-end component of their air forces.

In fact, there are cases when a single aircraft provides both a high- and low-end component of a nation’s air force, defying simple categorization. For example, the Hellenic Air Force is overwhelmingly comprised of F-16s, large quantities of which typically represent a low-end attribute. However, they also operate four distinct variants of the F-16, some of which are their most complex and capable high-end aircraft.

By contrast, the high-low mix portfolio is sometimes expanded in the U.S. Air Force to include the A-10 Warthog as the low-end component of a fighter-centric high-low mix. This categorization too is flawed, but not for the obvious reasons. Generally, this is viewed as confusing missions that, while interdependent, are not mutually supportive in the way a true high-low dynamic purports to be. For example, at first glance, a plethora of A-10s does not make F-15C or F-22 fighters better at achieving air superiority. Yet it actually does, in a way, because the A-10 is specialized. Packaging the Warthog’s unique attributes within a blend of complementary mission-specialized and multi-role aircraft make the overall team stronger than it would otherwise be.

Another common view is to equate “high” and “low” with the spectrum of conflict. Unfortunately, this incorrect definition of the high-low mix is the one the U.S. Air Force has latched onto. Back in 2014, the service published the Air Force Strategic Environment Assessment, 2014-2034, followed by both a Strategic Master Plan and Future Operating Concept in 2015. The goal of these documents was to describe and plan for how the service will operate in the anticipated environment of 2035. As a cornerstone to these efforts, the Future Operating Concept contained a reaffirmation of how the Air Force viewed the high-low mix (note the use of “tailored” as a euphemism for “small”):

The future Air Force will retain tailored numbers of high-end assets to operate against adversaries that pose advanced threats to joint/multinational force efforts in any domain.  To conduct follow-on sustained operations, or a sustained irregular warfare effort in a permissive or semi-permissive environment, AF [Air Force] forces primarily will use lower-cost/lower-capability assets.

In this regard, the U.S. Air Force’s definition mirrors Sen. John McCain’s white paper (highlighted in Part I), both of which remain at odds with the origin and ideas of the concept. This logic implies that low-end aircraft bring nothing of use to the fight in a high-end conflict, which is a dangerously flawed categorization. After all, isn’t a surface-to-air missile simply a low-complexity single-use aircraft in a high-end fight?

What Happened?

The Air Force’s “parity apprehension” has diverted attention away from pursuing an acquisition approach that results in a truly strategic force structure. Instead, the service has chased the ever-moving target of high-end dominance through a tactical-level platform-versus-platform overmatch. As the byproduct of this endeavor, the defense industry produced a track record of aircraft programs with unsustainable growth in complexity, cost, and schedule. Of these, time is arguably the most important variable, and it has both tactical and strategic significance.

At the tactical level, time to fielding is affected by delays due to unforeseen program problems, often the result of creeping complexity. This leads to small erosions to already fleeting advantages. Think of the F-22’s seven-year delay and the consequent stripping of requirements to reach initial operational capability — it lost datalink connectivity to fourth-generation fighters, infrared sensors, and the ability to operate in a chemically/biologically contaminated environment.

The primary justification for using concurrency in the F-35 program was that it would help to overcome this death spiral. Though the program has made positive strides in the past few years, few would argue that it has been a resounding success as a whole. The original F-35 program projected 1,013 fighters delivered by fiscal year 2016, a far cry from the mere 179 low-rate production copies produced to date. Right now, the F-35 program is delayed seven years and counting. Further, the Air Force’s own F-35A has declared its achievement of initial operational capability, but it appears this milestone was largely achieved by watering down the requirement of what constitutes combat-capable — an effort to recoup time lost.

Time is a commodity that also possesses strategic-level dynamics. Senior leaders often cite the example of the B-52 bomber, U-2 spy plane, and KC-135 tanker today as comparable to using a World War II B-17 Flying Fortress in Desert Storm. Less discussed in the open is that this is not an aberrant result, but the consequence of misguided planning built on several flawed assumptions. Left unchecked, it will continue.

The Air Force’s first F-35 was delivered in 2011, production is set to last through 2038, and the plane is projected to operate through 2070. This is akin to operating and maintaining a fleet of P-51 Mustangs from 1940 through the opening operations in Afghanistan in 2001. This is the plan, not a byproduct of unforeseen circumstances. Forty years from now, one can imagine a senior Air Force leader pandering a vignette comparable to the one with the B-17 ­in Desert Storm, as if we hadn’t planned to use current aircraft through 2060 or beyond.

This effort discounts the reality that the ability to operate in a contested environment is directly related to the capability (as opposed to platform) advantage one force has over another. As Col. Mike “Starbaby” Pietrucha astutely points out:

While the Air Force is constantly attempting to technologically outmaneuver our adversaries, it is unwilling to accept that we can also be technologically outmaneuvered — and that we have been. The Air Force should be dealing with the reality that no military advantage lasts forever.

The current Air Force acquisition strategy doesn’t follow any clear logic. It is a victim of a budget-based strategy reactive to program overruns and therefore decoupled from any chance of actually achieving the aims of the National Security Strategy. More likely, this parity apprehension is the result of the gluttony of the second offset: a Cold War strategy that emphasized quality over quantity and the promise of a small force armed with precision and stealth, capable of countering a quantitatively superior adversary. As a byproduct, the force has succumbed to a rampant and self-reinforcing spiral of cost, complexity, and capability.

Augustine, Again

Previously, we discussed one of Norman Augustine’s laws, which succinctly describes the complexity acquisition death spiral with which large segments of the U.S. military now grapple. Unaffordability predicted by Augustine is driving the U.S. Air Force to make “once in a generation” purchasing decisions that tilt toward overly ambitious and overly complex systems. Two important outcomes from Augustine’s law fuel this self-reinforcing cycle.

First, new acquisition programs are so expensive, time-consuming, and fraught with risk that the Air Force would rather modify existing aircraft to increase performance in certain areas or to enable new missions. If we could channel the thoughts of both Norm Augustine and Yogi Berra, we might say, “New aircraft programs are so rare, customers can’t afford to do one anymore.” The irony is that the customer should have the power to dictate precisely when new programs start, but the prevailing conditions have instead created a broken environment wherein market forces are no longer at work.

Second, modifying existing aircraft for new missions and capabilities inevitably pushes them toward the high end of the mix. They become more complex and expensive, but may lose their performance edge in the narrow slices for which they were originally designed. Further, this complexity may make them less reliable, and legacy platforms no longer in production are much harder to replace in the event of attrition.

The Light from the Night(hawk)

So, the logical question: Is there hope? Yes.

In the context of the original high-low mix definition, the F-117A Nighthawk could be categorized as the hallmark platform in that it truly decoupled performance, complexity, and cost. Naysayers could argue that at $43 million apiece ($103 million in 2016 dollars), it was about double the projected cost and exponentially more expensive than the new fighters the Air Force was buying at the time. But this oversimplification reveals the bias of the cost-complexity association that is rampant today.

The F-117 achieved initial operational capability in March 1982, an astonishing six years after the first sketch was made — and exactly on time as specified in 1978. That included building and flight testing two prototypes and three full-scale demonstrators before the first production F-117 was delivered. It just so happens to be the last aircraft program to field in less than ten years. Even more remarkably, the program achieved this success entirely under the cloak of secrecy, even standing up a new unit to operate the aircraft. By comparison, it took 14 years to achieve initial operational capability on a stealth cruise missile. So how was this possible?

Simple: The F-117 was advanced only in the scope of its purpose, leaving it unbridled from unnecessary complexity. The entire governance of the program and developmental cycle was singularly focused on signature management (radar, thermal, acoustic, and even visual). To achieve this feat, the program used off-board risk reduction wherever possible by repurposing an extensive list of mature components from other platforms.

The F-117 used a modified F-16 flight control system and cockpit controls, F-18 engines (sans afterburners) and heads-up displays, the C-130’s environmental control system, brakes from the F-15, F-111 flight control actuators, a B-52 inertial navigation system, and cockpit navigation/communication gear sourced almost entirely from other aircraft programs. Additionally, it’s estimated that 95 percent of the ground support equipment used was also common to other fielded aircraft.

Even the F-117’s unique GBU-27 bomb was not so much developed specifically for the F-117 as it was adapted for  it. After all, a bomb does not inherently contribute to signature management. This penetrating laser-guided bomb was simply made from another 2,000-pound bomb variant, the GBU-24. Since the GBU-24’s massive tail fins would not fit into the F-117 weapons bay, a legacy 2,000-pound GBU-10 bomb tail fin was used, and the GBU-24 seeker logic was modified to account for the new flight characteristics.

The final and the most important footnote is the tradeoffs the F-117 program made to achieve this unprecedented program agility. It sacrificed cockpit visibility and ergonomics (which proved causal to numerous mishaps), lacked a radar for targeting or all-weather navigation refinement, and was relegated to subsonic flight. Most surprising of these sacrifices, the F-117 had no warning receiver to tell a pilot if he was detected by radar or under fire from guided missiles.

You could say the F-117 was designed to perform, not designed to last. Much more than the sum of its (well-proven) parts, it served its purpose in Operations Just Cause, Desert Storm, Allied Force, Enduring Freedom, and Iraqi Freedom. It was retired in 2008, after 26 years of service — a worthy return on investment. For comparison’s sake, that would be akin to retiring the F-22 in 2031 or the F-35 in 2042.

When viewed under the auspices of the original defense reform movement, the F-117 is actually an inverse example of the original high-low mix design. It was expensive, though not comparatively complex. It was a narrowly scoped high-end platform to support a single mission, rather than a multi-role platform. And throughout its life, it was often supported by other mission-focused platforms, such as the EA-6B.

We can break the techno-fetishism that led to the acquisition death spiral in tactical aircraft by decoupling the numerous misconceptions surrounding the high-low mix and by acknowledging the misapplication of generational acquisition strategies focused on platforms instead of on capabilities. Today, there are indications that the B-21 Raider program may draw on some of the aforementioned F-117 programmatics by using mature systems and technology where readily available and investing resources in advancing the attributes of the program that are the basis for its being. This would be a welcome change, though time will tell.


Scott Bledsoe is the President of Blue Force Technologies, a North Carolina-based aerostructures and aircraft R&D firm. He has led novel design / build activities for aircraft in the VTOL, supersonic, and low-observable regimes, as well as space launch systems. 

Maj. Mike “Pako” Benitez is an F-15E Strike Eagle Weapons Systems Officer with over 250 combat missions spanning multiple deployments in the Air Force and Marine Corps. He is a graduate of the U.S. Air Force Weapons School and a former Defense Advanced Research Agency (DARPA) fellow.

The views expressed are those of the authors and do not reflect the official policy or position of the Department of Defense or the U.S. government.

Image: U.S. Air Force photo by Master Sgt. John Gordinier

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