Fly Off: F/A-18E vs. 18C

The single-seat F/A-18E program should be re­configured into a fly-before-buy prototype pro­gram because of the uncertainties concerning the aircraft’s predicted 28% increase in combat radius and its margin for growth. The Navy should develop com­bat-capable prototypes and conduct a flyoff against the F/A-18C to determine if the actual improve­ments are worth the added cost.

Given the dire predictions for the future of naval aviation, can we afford the time to do this? In February 1992, Sec­retary of Defense Dick Ch­eney said: “With the collapse of the Soviet Union ... the need to produce new systems quickly is less urgent now ... we can con centrate on R&D [research and development], on operational testing, and the development of prototypes. . . . We’ll move to large-scale production of new weaponry only when we get what we want at a price we can afford.’’

Critics of prototyping the single-seat F/A-18E contend that the F/A-18A/C mod­els have already served as prototypes—and thus there is no requirement to go through the drill again. But the F/A-18E is not just a cosmetic upgrade; it has a redesigned wing, new engines, new inlets, and significant changes in its structural materials. It is in many respects a new aircraft—and the $5 billion research-and-develop- ment price tag reflects this. Moreover, those who argue that the F/A-18A/C were prototypes for the E model should remember that these aircraft did not meet range require­ments, had a steady history of weight growth and de­creasing range capability, and cost 40-50% more than pre­dicted. This experience counsels caution.

Here are specifics on the combat radius and growth mar-

Editor’s Note: Concerned about the reliability of predicted perfor­mance figures for the Navy’s F/A-18E/Fprogram, Mr. Spinney recom­mended that an independent panel of disinterested experts conduct a detailed risk analysis. The panel had only two weeks—rather than the recommended two months—to conduct its evaluation, and briefed the author in late April 1992. Mr. Spinney wrote his conclusions in a 29 April memorandum obtained by Proceedings. An edited version of that memorandum is published here.

gins. First, the combat radius is suspect because the air­craft’s fuel fraction will increase by only 4.9%, its en­gines will have a higher specific fuel consumption (SFC), and its thrust-to-weight ratio will decrease. (See Table 1.) Granted, the aircraft is being fitted with a new wing that is predicted to improve the lift-to-drag ratio by 23% at 10,000 feet and 7% at cruise altitude, and has undergone extensive wind- tunnel work, but, even though Gary Erickson, Senior Research Engineer at NASA Langley’s Transonic Aerody­namics Branch, the panel’s aerodynamics expert, made a persuasive case that risk has been reduced, the impact of these changes will not be completely under­stood until we fly a full-scale prototype F/A- 18E.

In addition, the Navy’s claim that a digi­tal fuel control will offset some of the F/A-18E’s engine disadvantages, partic­ularly in the non-cruise portion of flight, is spurious because existing F/A-18C’s could also be retrofitted with an equiva­lent digital fuel control.

Second, even though the increase in combat radius is theoretically achievable, the engineering margins appear to be so tight that the normal possibilities for unexpected weight growth, aerodynamic degradations (i.e., drag in­creases or lift decreases), and engine degradations (in ei­ther weight, thrust, or SFC) compound the technical risk surrounding this program.

>• The potential for weight growth is high because the structural design is essentially that of a new aircraft with major changes in material composition. The allowance for weight growth is below average: the 1,050 pounds bud­geted is a 3.6% weight reserve, while contractors normally budget 4.5%. This is troubling in light of McDonnell Air­craft’s history of range-weight problems. As mentioned, the F/A-18 has track record of weight growth, and the company did not meet the range specifications for this air­craft or for the initial version of its F-15—which required 2,000 pounds of additional fuel.

>• The impact of the preplanned product improvement—

Table 1: F/A-18E vs F/A-I8A/C

F/A-18E      F/A-18A/C Change

Fuel fraction

Takeoff weight (fighter escort)	.302	.288	+4.9%
Maximum fuel	.44	.42	+5.6%
Thrust specific fuel consumption
Best cruise, ait., Mach; full int. fuel	1.0956	1.0578	+3.6%
Mil. power at M=.7/20K/60% int. fuel	1.0618	1.0383	+2.3%
Max A/B at M=.9/20K/60% int. fuel	2.063	1.983	+4.0%
Thrust-to-weight ratio
Takeoff, IRP, ftr escort, int. fuel	.50	.54	-6.5%
Takeoff, Max A/B, ftr escort, int. fuel	.75	.80	-6.3%
Mil. power at M.=.7/20K/60% int. fuel	.35	.36	-3.1%
Max A/B at M.=.9/20K/60% int. fuel	.68	.73	-6.5%

F/A-18E vs F/A-18C Characteristics*

	F/A-18E	F/A-18C
Wing Area	500 sq. ft.	400 sq. ft.
Weight
Empty	30,600 lb.	24,600 lb.
Max TOCW	66,000 lb.	51,900 lb.
Propulsion
(2) F404 Derivation
Turbofan Engine
Total Thrust (SLSU)	44,000 lb.	32,000 lb.
Fuel (JP-5)
Internal	14,500 lb.	10,900 lb.
External
330 gal. tanks	6,700 lb.	6,700 lb.
480 gal. tanks	9,800 lb.	”
Design Load Factor (USN)	7.5 g	7.5 g
% Spotting Factor	119%	100%

1,810 pounds—on any requirement for a larger wing and engine was not analyzed. Assuming the same engine and wing, the addition of 1,810 pounds would reduce thrust- to-weight ratio from .50 to .486; increase the wing load­ing from 96 to 99 pounds per square foot; and reduce the

fuel fraction from .302 to .291. On the other hand, if preplanned growth comes out of the bring-back allowance it will reduce the weapons bring-back load by about one-half, thereby undermining one of the E model’s justification.

>• While the independent panel believes the en­gine risk is low to moderate, it has not been tested in an all-up configuration and may have its own weight problem.

In addition, the Defense Department has not compared the F/A-18E with an advanced tech­nology F/A-18C. For example, F/A-18E R&D dollars might be better spent by: equipping all F/A-18Cs with upgraded digital fuel controls; de­veloping lighter avion-

ics and secondary struc­tures that would improve the F/A-18C’s thrust-to-weight ratio, wing loading, and fuel fraction; or simply buy­ing more F/A-l&Cs.

While the F/A-18E’s new wing introduces the possibility that the air­craft’s range will im­prove, the adequacy of the margins is still an open question. David LeMaster, Chief of the Air Force’s Flight Tech­nology Division at the Aeronautical Systems Division (ASD) at Wright-Patterson Air Force Base, Ohio, the panel’s performance ex­pert, seems to agree that the structural weight margin—1,050 pounds— is slim, and that the contractor would have to be very careful with configuration changes. On the other hand, James Day, Director of Engi­neering in the Subsystem Project Office at ASD, the panel’s propulsion expert, indicated that the engine margins were more than adequate, because the Navy used a “minimum engine” in its analy­sis. Day believes that this liberal margin might provide enough of a cushion to offset the slim structural margin. While this belief seems rea­sonable, no detailed analysis measuring the size of this cushion has been completed. The proto­typing program, if approved, would render this issue moot.

The panel members’ objectivity and profes­sionalism were impressive, and there is no rea­son to doubt their findings; the peculiar circumstances of the handling of their findings supports the following ob­servations:

At least the following changes have been made relative to the wing of the F/A-18C: Leading-edge sweep will be

increased from 26.7° to 29.4°, taper will be increased, twist will be removed, thickness-to-chord ratio will be in­creased, a snag on the outboard leading edge of the wing will be added, the ratio of exposed wing to total wing area will be increased, and the leading edge extension along the fuselage will be shortened.

Erickson believes these changes, while small individu­ally, should combine with the effects of improved flap scheduling to change dramatically the aerodynamics of the F/A-18E—if the wind tunnel and theoretical calcula­tions translate into real-world performance improvements.

He believes the wind-tunnel work done to date is very conservative and should be reliable. It should be remem­bered, however, that data from the best wind-tunnel mod­els (particularly drag estimates) do not always scale ex­actly to real-world performance. The F/A-18A, for example, had more drag than predicted by similar but less complete analyses, and this was one reason why it did not meet its range goals. Erickson was confident that the ex­perience with the F-18A and the subsequent calibration of the wind tunnels by comparing F-18A flight test data to wind tunnel data provided a greater level of assurance that F-18E wind tunnel data would translate more closely to real-world flight test data than that of the F-18A. There is a persuasive case that aerodynamic risk has been reduced, but the numbers will not be known until the real aircraft flies.

Moreover, this new and aerodynamically different wing should be placed in the context of four other changes: ^ The fuselage will be lengthened almost three feet, but its width will remain the same. Thus, the F/A-18E will have an increased fineness ratio.

^ The air inlets to the engine will be much larger and the exterior shape will be changed from a semicircle dom­inated by smooth curves to a four-sided parallelogram dominated by straight lines and sharp angles.

^ The F/A-18E will use a new engine, with a core derived from the engine used in the now defunct A-12 program, and an afterburner added.

^ The composition of the empty-weight aircraft will in­clude a higher percentage (by weight) of composite ma­terials used in the skin sections.

While some of the avionics remain the same, and even though its design is technically a derivative of an exist­ing airplane, the cumulative effect of a new wing, new engines, new inlets, and new structures makes the F/A- 18E more like a new airplane than a modification of an existing airplane. This suggests that it would be more appropriate to consider the aircraft a “new start,” (perhaps a hybrid Milestone I/II decision) rather than the curious Milestone IV/II hybrid that is now contemplated. (It got a green light, but the Navy has not signed the contract pending the outcome of the AX cost-and-operational-ef- fectiveness analysis.)

The F/A-18E prototype program would be the center­piece of a new, comprehensive, acquisition strategy in­tended to extract the Navy from the looming crisis in its tactical aviation force structure. Figure 1 portrays the Navy’s estimate of how its fighter-attack inventory will begin to collapse early in the next decade. It is crucial to understand that this meltdown is not the product of re­ductions in the budget. Figures 2 and 3 show that the real source of this crisis is a 40-year mismatch between cost growth and budget growth. (The reader should note that, because of data limitations, these charts describe this prob­lem in terms of the Navy’s entire aircraft procurement program.) As long as costs increase faster than budgets, increases in the budget will not produce proportional in­creases in the number of new aircraft purchased, and de-

creases in that budget will magnify the decline in that number. The only solution to this mismatch is to attack it at its source. If the Navy wants to remain viable in the next decade, it must figure out how to reduce its costs. The new acquisition strategy is designed to determine if this is possible.

Its objective would be to break the crisis by providing the Navy with options for reducing costs while adapting its capabilities to the new threats and budgets of the post­Cold War world. The new strategy would include two hedging options to protect the Navy in case the F/A-18E fails to live up to expectations.

First, recognizing that there is little maneuvering room during the intermediate-term planning horizon, the F/A- 18C would remain in production during the prototype de­velopment phase to make up for any lost F/A-18E production.

Second, to provide longer-term protection, $100-$ 150 million would be divided among four-to-six contractors (awarded on the basis of competitive bids) for the pur­pose of producing preliminary designs for two new air­craft—one a conventional, carrier-based aircraft designed for direct support of Marines in a littoral scenario, and the other designed for local air superiority (with a secondary bombing capability) in the same scenario.

Although these design efforts would be aimed at tai­loring aircraft to the unique capabilities of Navy and

Marine Corps forces to intervene in a variety of littoral scenarios (as opposed to duplicating the Air Force’s deep-interdiction bombing capabilities), they would also be aimed at determining if available technologies can be combined with improved acquisition strategies (a greater reliance on commercial specifications, for example) to re­duce costs while increasing the variety of pragmatic modernization options. The money to fund the conceptual designs would come from the near-term savings result­ing from conversion of the F/A-18E engineering, manu­facturing, and development (EMD) program to a proto­type program. Finally, it would be understood by all participants that these design efforts do not imply a com­mitment to future procurement.

Current AX plans would also continue to be refined. While these efforts were under way, the Department of the Navy, the Joint Chiefs of Staff, the Office of the Secretary of Defense, and the Institute for Defense Analy­ses would use these options, i.e., the F/A-18E, F/A-18C, AX, the local air superiority fighter (ASF), and the di­rect support fighter (DSF) as the building blocks to pro­duce a series of independent studies, the objective of which would be to determine how the Navy-Marine Corps tac­tical aviation force structure should evolve.

These studies would examine the force-mix tradeoffs of moving between two extremes. At one pole would be a projection of the status quo—the mix of F/A-18C/Ds, F/A-18E/Fs, AXs, F-14s, and A-6s shown in Figure 4, and at the other would be a force structure designed to pro­ject power in support of Marine ground forces employed in a variety of littoral scenarios—some combination of F/A-18C/Ds, DSFs, ASFs, and perhaps F/A-18E/Fs. In­termediate points between these extremes would also be examined, and the studies would set the stage for a true intellectual competition—a free trade in ideas, so to speak, premised on Oliver Wendell Holmes’s theory that “. . . the best test of truth is the power of the thought to get itself accepted in the competition of the market.”

The ultimate objective of this debate would be a real­istically attainable, fiscally pragmatic modernization plan- one that accounts for the threats, missions, force struc­tures, and budgets that are likely to shape the Department of the Navy’s tactical aviation for the next 20-25 years.

The principal objection to this plan is that it would delay the introduction of the F/A-18E into the fleet. While this is true, the consequences of a delay should be evaluated in the context of its effect on the Navy’s capabilities and the limitations of its current plan. If a prototyping pro­gram is pursued vigorously and enthusiastically, it should add only about two or perhaps three years to the current program. During the interim, additional F/A-18C produc­tion would make up for any losses caused by the defer­ral of F/A-18E production.

Given the large number of Navy-Marine Corps aircraft, the substitution of a relatively small number of F/A-18Cs for F/A-18Es would have a negligible effect on the com­position of the inventory mix. In view of the diminishing threat and the superior performance demonstrated by our aircraft in the recent war with Iraq, the impact of this delay cannot be deemed significant except under the most ex-

treme and improbable assumptions. Moreover, even if the F/A-18E and AX enter the inventory on schedule, and the Navy embarks on a massive service-life-extension pro­gram (SLEP) for its remaining F/A-18 aircraft, its current modernization plan does not produce enough aircraft to support the base-force inventory goal (see Figure 4), and that plan is based on two questionable economic as­sumptions—that the aircraft modernization budgets (mea­sured in constant dollars) will trend upward until 2010, and that the procurement quantities within these budgets can be determined by “rough order pricing only”—a sit­uation made worse by the fact that current moderniza­tion plans do not provide any funds for either the F/A-18 SLEP or the Marine Corps medium-lift modernization pro­gram (see Figure 5).

Taken together, a marginal impact on effectiveness and highly uncertain budget assumptions suggest that any delay accompanying a prototype program would be an advan­tage, not a disadvantage. It would buy time to generate more reliable information—lessening the unavoidable eco­nomic uncertainties that undermine far-term projections, and giving the Navy the time it needs to sort out a strat­egy for achieving its force goals. The Defense Depart­ment’s increasing dependence on long-term projections is one consequence of buying ever more complex weapons. The steady increases in costs and development lead times force planners to decrease the variety of new weapons while projecting the consequences of their current deci­sions (budgets, costs, and procurement and inventory quan­tities) ever further into the future. Plans become more vul­nerable to disruption because they are premised on fewer alternatives and increasingly uncertain economic as­sumptions. Figures 4 and 5 illustrate the result—to justify the commitment of resources in fiscal year 1992, planners must project the consequences of that decision out to fis­cal year 2010 to prove that their plan is “affordable.” This is being done even though the Defense Department has not successfully executed a single five-year plan for at least 15 years—and we are entering an era of unprece­dented change. Does anyone really believe we can predict budgets and costs out to 2010? While uncertainty can never be eliminated, one advantage of prototyping is that it buys time to reduce its pernicious effects to more manageable levels. This idea will be developed more fully.

Cost? Some may argue that a prototype program will increase the cost of the F/A-18E over the long term. In fact, prototypes are used to reduce costs in private indus­try. Rigorous prototyping is a central strength of Japan­ese auto manufacturers, for example. Moreover, they in­troduce new models more quickly than their competitors.

Long-term cost control is primarily a function of the management discipline imposed by the U.S. government. If we hold the contractor’s feet to the fire, and we main­tain options for alternative solutions, so that the threat of cancellation is real should we deem his program to be un­desirable, the contractor will be under tremendous com­petitive pressure to please us, and he will do his best to hold down costs while trying to meet design specifica­tions. That is what real competition is all about.

On the other hand, by removing options at an early stage, concurrent engineering and manufacturing devel­opment programs create a situation where there are no al­ternatives when the “production decision” is to be made. This hands the contractor power to squeeze the govern­ment, and therefore reduces his incentive to control costs.

Prototyping “whenever possible” is now Defense De­partment policy as enunciated by Secretary Cheney, and the F/A-18E is ideally suited for a combat-capable pro­totype program for several compelling reasons:

Suitability. While it is nearly a new aircraft from the perspective of aerodynamics and propulsion, the weapon- system integration will make much use of existing F/A- 18C’s systems. Systems integration is normally a major impediment to prototyping combat capabilities, but in this case that impediment is not significant.

Sound Engineering Practice. Prototyping is preferred engineering practice and should always be used unless the pressures of time make the acceptance of the higher risks of concurrent engineering mandatory. It is important to understand that producing a prototype does not mean that production engineers are not involved in the product’s de­sign. They should be involved from day one to ensure that the ultimate design is producible. The goal of prototyp­ing is to work out the bugs before large dollar resources are committed to its production. Once a product is in se­rial production, the cost of fixing design flaws on work- in-process or fielded systems rapidly escalates, particu­larly if assembly-line equipment must be changed. In contrast, prototypes are built under job-shop rules, where highly skilled labor and general-purpose machine tools are substituted for production workers, specialized ma­chinery and specially designed factory layouts.

Freedom of Action. This plan reduces the price of technical risk by increasing freedom of action over the long term. By avoiding the higher up-front costs of a con­current engineering and manufacturing development pro­gram, a prototype program—coupled with the preserva­tion of F/A-18C manufacturing capability and new design options—protects future decision makers from the possi­bility that high sunk costs and local economic pressures will force them to accept an aircraft that does not meet its performance specifications. Our acceptance of the reduced range specification for the C-17 transport—a practice know in the Pentagon as a rubber baseline—is an example of the price we pay when we have no options.

Competition. The existence of lower-cost production options such as the F/A-18C and the exploration of new aircraft design options will put pressure on McDonnell Douglas to hold down costs and meet the specifications of the F/A-18E. Moreover, by sponsoring preliminary de­sign work in different companies, we are helping to pre­serve a perishable national resource—the preliminary design teams in the aircraft industry. These teams are the heart of a company’s culture; they take years to build up, and they embody the spirit of each company’s pecu-

liar approach to aircraft design. They are the source of new ideas as well as what little competition remains in an increasingly bureaucratized industry. When they dissolve, the bonds of mutual understanding and outlook evaporate and can only be reconstructed at considerable cost over a long period of time.

Adaptability and Viability. In contrast to the rigid commitments of a concurrent engineering and manufac­turing development program, a fly-before-buy prototype program for the F/A-18E, combined with the other facets of this recommendation, will provide the Navy with the flexibility it needs to sort out its plans as it moves into an era of unprecedented uncertainty and programmatic confusion.

It is no longer clear what future threats will exist, how large future budgets will be, or how the Navy should re­late to this emerging world. Proponents of the F/A-18E have compounded this unavoidable uncertainty with con­fusion by making contradictory cases for buying the aircraft:

• One faction argues that the F/A-18E is the only solu­tion to the Navy’s looming force-structure crisis, be­cause a single multi-role fighter will cost less than a high- cost (read unaffordable) F-14/AX combination.
• Yet another faction argues that the F/A-18E is the only solution to the crisis, because it will provide a bridge to a future force structure based on the high-cost AX and, perhaps, a new fighter—the NATF or even a version of the F-14.

While these agendas are based on mutually exclusive views of the future, neither faction has constructed a re­alistic strategy for reaching the base-force goal. In this re­gard, planners would do well to remember what happened

after the F/A-18 program was sold to decision makers in the 1970s as the low-cost solution that would prevent the emerging crisis from occurring in the first place. It should be remembered that the F/A-18 procurement was sold as being necessary to preserve a force structure of 14 to 16 carrier air wings, not the base force of 13 wings now contemplated.

The F/A-18 program was conceived during the mid- 1970s as the centerpiece of a long-term plan to buy enough airplanes to avoid a force-structure crisis during a force expansion. The intention was to produce F/A-18s at high rates to compensate for the low-rate production of the F-14, AV-8, and A-6 aircraft. But when it be­came clear early in the 1980s that the F/A-18 would cost much more than originally planned, the Navy chose not to cancel other programs to release the money required to execute this strategy. Conse­quently, the high rates predicted in the out years of successive five-year defense plans never material­ized, notwithstanding strong support from con­gressional appropriators (see Figures 3 and 4).

The resulting inefficiencies of lower-than-planned production then kept costs higher than necessary (even after accounting for the cost growth), and by the 250th unit, the actual costs of the F/A-18 were exceeding planned costs by about 40%, after tak­ing out the effects of inflation. A case can be made, therefore, that optimistic cost predictions, particu­larly those made when the program was being sold, and unrealistic out-year budget expectations rein­forced each other to make the F/A-18 part of the problem rather than the solution.

Now both factions in the force-structure debate, for very different reasons, contend that an F/A-18 engineering, manufacturing and development pro­gram is the only solution to yet another looming crisis. But first—we must increase its cost even more! If, like earlier F/A-18s, the actual costs of the F/A- 18E turn out to be higher than predicted (remember, cur­rent plans assume the “rough-order” prices of a pre-EMD estimate), or out-year budgets turn out to be less than pre­dicted (remember, current plans are based on projections out to 2010), the result could be a force-structure deba­cle, even if the F/A-18E performs as predicted.

By closing out other options, the agenda of either fac­tion will lock us into a high-risk strategy and repeat the formula that caused the problem. On the other hand, the strategy recommended here is designed to reduce risk, pre­serve options, explore alternatives, and stimulate an open, vigorous debate on the effectiveness and affordability of these alternatives. It is a more pragmatic approach to in­creasing the Navy’s viability as it moves into the next century.

Mr. Spinney is a civilian program analyst in the Tactical Air Division of the Defense Department’s Office of Program Analysis and Evalua­tion. A former U.S. Air Force officer, he has written widely on defense planning and decision making and has testified before Congress on nu­merous occasions. He wrote “A Defense Strategy That Works,” Janu­ary 1990 Proceedings.