One of the more remarkable aspects of modern aircraft carriers is the manner in which these ships have served as the setting for the appearance of a startling number of generations of aircraft. Through the years, aircraft like the Brewster F2A Buffalo and the F4F Wildcat made their entrance, spoke their lines, and exited, as they were replaced by other, newer planes. In the 1940s, the F6F Hellcat and the F4U Corsair, along with the SBD Dauntless, the SB2C Helldiver and the TBM Avenger, wrote history in flights from some of the same flight decks that today launch and recover the F-8 Crusader and the A-4 Skyhawk. The newer attack carriers that operated F2H Banshees, F3H Demons, F7U Cutlasses and F9F Panthers and Cougars less than a decade ago, have moved into the Mach 2 plus era with the F-4B Phantom II and the RA-5C Vigilante. A cavalcade of improving jet and propeller aircraft has come and gone while the ships evolve to suit each new generation.
From the pilots and maintenance personnel who learn to operate each of these new aircraft to the taxpayers who pay for them, the questions must occasionally occur, "Where does the requirement for a new aircraft generate? Who decides that we need a new model—and why?" Unlike Detroit, where new model automobiles are brought out and displayed annually as a matter of course, aircraft models appear sporadically in accordance with what may seem to be a haphazard schedule.
In fact, each new aircraft is brought into the over-all inventory in accordance with a general plan and in response to a specific requirement. Discussion of this system and of the formal derivation of these requirements provides an insight into the Navy method for developing its new weapons systems of all sorts. Such a discussion should provide many answers to both Navy men and taxpayers of the United States in general. It must be appreciated that a period of more than ten years may elapse between the initial appearance of an aircraft weapons system in its conceptual stage, and actual, Fleet-wide employment of that aircraft. Time spans for other weapons systems can be longer than this, or shorter, depending upon their nature and the urgency with which they are pursued.
In this period of time, obviously, circumstances and environment may undergo appreciable change, breakthroughs in scientific technology may bring new developments into reach or render proven techniques obsolete. Additionally, altered political and military circumstances such as involvement in a conflict with specific rules of engagement (e.g., Cuba, Vietnam) may affect specific requirements in an unforeseen manner.
In the late 1940s and throughout the 1950s, there was general conviction among both military and civilian executives that nuclear weapons would be the primary weapon employed in any major conflict. In many circles, it was held that there could be no major conflict without the wide employment of nuclear weapons. Our national policies were centered on that concept. The Korean War assumed the dimensions of a major conflict in many respects, but its confinement to conventional weapons was considered an exception to the rule. This preoccupation with nuclear weapon techniques affected the generation of aircraft requirements to a considerable degree, and weapons systems with nuclear application received the most serious attention. Attack aircraft requirements were concerned primarily with penetration and delivery to a target of a nuclear weapon, fighters were designed primarily for the task of intercepting incoming bombers before they could deliver a stunning nuclear blow.
As originally conceived, the A-4 Skyhawk was a manifestation of the "Massive Retaliation" concept of the decade that began at Alamagordo when the first nuclear detonation was achieved. The initial design concepts stemmed from the work of a single aeronautical engineer. Known as "Heinemann's Hot-rod," after the aeronautical engineer who was instrumental in its design, the Skyhawk was first accepted by the Navy in 1954, and the aircraft represented complete, single-minded application of the requirement for a simple, easily maintained carrier aircraft, able to carry a single nuclear weapon (and very little else) and deliver it on a target, relying primarily on the navigation of a skilled pilot, highly trained to hit his particular target. As such, the A-4 had no radar and was equipped with minimum instrument and night flying capability and virtually no navigation gear, other than compass and air speed. The aircraft required the addition of a bomb-shaped NAVPAC, which, carried on the external nuclear bomb station, enabled the pilot to fly on airways in instrument conditions within the continental United States.
Another product of requirements generated by the nuclear deterrence and its implications, is the A-5A (A3J) Vigilante, designed toward achievement of another system for delivering nuclear weapons to heavily defended targets that would be struck only once, with devastating finality. As its mission changed from nuclear to limited war, the Vigilante was modified to the RA-5C, a sophisticated multi-sensor reconnaissance aircraft for employment from large carriers.
Due in part to Navy mission requirements for support of the Marines and of amphibious warfare concepts, some attention was still devoted to conventional warfare capabilities. During this period, Navy requirements writers never lost sight of the objective of maintaining an adequate conventional weapons delivery capability, and the competence of aircraft embarked in our carriers today is the result of this knowledgeable hardheadedness, some good design and considerable modification. Thus, the A-4E of 1966 is similar to the A4D-1, circa 1956, which was oriented toward the nuclear mission. The A-4E has better fuel specifics, additional bomb pylons, an air refueling capability, and better avionics, which make it entirely suitable for conventional weapons delivery and support of ground troops, both major roles in Southeast Asia today. Other aircraft, both fighter and attack, have been similarly modified to enable them to cope with an environment somewhat different from that which obtained when they were designed.
A later aircraft, the A-6A Intruder, represents a complex development to fulfill a Navy/Marine requirement for an all-weather attack plane, capable of finding and hitting targets under virtually all conditions of weather and visibility with sufficient accuracy to permit close support of ground forces and night interdiction. With long range and a heavy bomb load of nuclear or conventional weapons, the Intruder was designed to a specific requirement, tailored to a military need based on experience in the Korean War. The complex avionics installation of the A-6A received its first combat in South East Asia in 1965 and proved the legitimacy of the requirement that led to its development.
In the fighter role, ample demonstrations of the application of portions of the requirements process are also available. Almost all of the fighter engagements of World War II, as well as the relatively smaller number in Korea, were fought with .30 or .50-caliber guns and 20-mm. cannon. Fighter aircraft requirements then trended toward application of the newer systems that were becoming technically available, employing air-to-air missiles. The F-6D (F4D) Skyray, first accepted in 1954, was designed to incorporate high aircraft performance and the unguided 2.75-inch rocket in a single system. Skyray performance was demonstrated in 1958, when the aircraft established a number of world records for times to climb to various target altitudes.
As missile technology advanced, the F-3B (F3H) Demon combined the guided Sparrow missile and the aircraft radar search and guidance systems needed to make it work. The F-8 (F8U) Crusader series incorporated a wing with two positions to allow varying angle of attack and solve the over-the-nose visibility problem encountered in carrier landings with high performance aircraft. And the F-8 was designed to employ the heat-seeking Sidewinder missile. Many other fighters were designed and developed as each new jet aircraft and missile system added inputs to the sum of Navy capability in this field. Basic Fleet requirements evolved rapidly in the search for aircraft that would provide the caliber of fleet defense required, while remaining compatible with the carriers. During the period from the late 1940s to the early 1960s, more than 20 distinct jet, composite, and turbo-prop fighters were developed and flown by the Navy, as technology took rapid strides forward and development raced to keep up.
Eventually, two programs aimed at providing a Fleet aircraft able to operate in the Mach 2 speed range, were pursued. The Crusader III (P8U-3) and Phantom II (P4H-1) represented single-engine, single-pilot and twin-engine, two-man approaches to the problem of satisfying the requirement for a very high performance, all-weather, missile-armed fighter. After a difficult evaluation, the Phantom II was chosen, put into production and has become one of the foremost military aircraft in the world.
The general procedure for the generation of an aircraft requirement begins with recognition of the need for a follow-on or new aircraft. The origin of this recognition stems from a continuous evaluation of current system capabilities, the threat, technological progress and the Navy mission. This evaluation must continually ask the question, "What has changed?", and then, "Are Navy requirements affected?" As enemy capabilities change or improve, the Navy's ability to cope with the new threat must be evaluated. When research indicates significant improvements in capability are available, their application must be assessed. If a new mission becomes apparent, it may generate new requirements. This sort of a continuous evaluation of what the Navy has versus what is available and what may be needed, is the best way we can ensure that requirements remain valid and applicable to our needs. This process must also be continuously measured against the fiscal facts of life, and the Navy must make in each case a preliminary decision as to whether a given net gain in capability represented by a specific program is worth the cost of the program and the possible sacrifice of other programs. Only when that decision is made in the affirmative, does the process of documenting a requirement ensue.
A new requirement, based on the evaluation described, may originate in the Fleet, on the drawing board of an engineer, in the Joint Chiefs of Staff, in Air Systems Command or the Office of the Chief of Naval Operations (OpNav), or as a result of a national policy decision. Research may develop the theory for a new weapon or device that has application in an aircraft, as, for example, the fan jet engine, or a Laser system. General Operational Requirements (GOR) documents are maintained for each functional warfare and support area and they define broad military needs in general terms of the capabilities required. These are based upon such planning documents as the Long Range Strategic Study and the Navy Mid-Range Objectives, as well as on Fleet inputs and policy decisions. They are subject to continuous review to ensure their currency.
When circumstances indicate its desirability, a Tentative Specific Operational Requirement (TSOR), is produced by the Chief of Naval Operations staff. This document states the need for achieving a particular operational capability and outlines the characteristics necessary in the system to fulfill the requirement. On occasion, research may indicate the need for further investigation of a particular technique or system, and the Chief of Naval Material may promulgate an Exploratory Development Requirement to point out the need.
Regardless of the origin of the query, the Chief of Naval Material responds with a document called a Proposed Technical Approach (PTA), which endeavors to set forth technically feasible alternative methods of accomplishing the objectives set forth in the TSOR, and to support its contentions with data on cost and effectiveness. Where the results of the TSOR/PTA exchange indicate, the Chief of Naval Operations produces a Specific Operational Requirement (SOR) which outlines specific system characteristics, defines Performance throughout the system operational environment and establishes goals for reliability, maintainability, training, and personnel requirements.
The Chief of Naval Material response to this document is called a Technical Development Plan (TDP), and it comprises the plan for fulfillment of the SOR. It is a detailed description of the effort necessary to accomplish the development, together with a recommended funding and completion schedule. This entire process is known as "Concept Formulation" and it includes the accomplishment of comprehensive system studies and the CNO/ChNavMat exchanges discussed.
Concept formulation is a prerequisite to any decision to carry out engineering development. Once this decision has been made, a process of "Contract Definition" ensues. During this phase, preliminary design and engineering are verified and firm contract and management planning are performed. The over-all objective of contract definition Is to determine whether the conditional decision to proceed with engineering development should be ratified. The ultimate goal is achievable performance specifications and firm fixed price or fully structured incentive proposals for engineering development.
All of these steps accomplished, a given aircraft weapons system arrives at the project execution stage, which includes issuance of a request for proposals and, finally, award of a contract and eventual production. Io time, an actual piece of military hardware, a fully equipped combatant aircraft, will result. Just what its capabilities are, how fast it will go, what it will carry and how far, these and other performance parameters will have been carefully established as a result of the combined capacity for analytical and technical work inherent in the OpNav organization, in Air And Ordnance Systems Commands and in such organizations as the Center for Naval Analyses, the Operational Evaluation Group and the Naval Warfare Group, and the various Navy facilities at Johnsville, Inyokern, Patuxent River, the David Taylor Model Basin, and elsewhere. A major contribution is often made by the aviation industry, both as a result of studies accomplished for the Navy on a contract basis, and those which are designed to find markets for the company's products.
Having traced the laborious pathway which an idea must traverse to become an aircraft in being, it is worthwhile to consider the manner in which certain of the aircraft-requirement documents are developed and the rationale which accompanies the precise performance criteria they state. The process begins with a particular operational capability or mission derived from the general planning documents previously mentioned. Based on consideration of the military, physical, and political environment in which the system may be expected to operate, certain tentative conclusions may be reached.
For an attack aircraft, for example, a certain weight of bombs must be carried to certain ranges and delivered on certain types of targets. How many bombs of what size? To what ranges? To be dropped on what types of targets? What degree of opposition may be expected?
At the outset, for any combat weapons system, consideration must be afforded to the enemy threat. Joint, agreed estimates of the threat posed by prospective enemies are available and are a part of stated operational requirements. The performance assigned by these estimates to enemy aircraft, missiles, guns, and radars is the result of educated examination of enemy capabilities and the, inputs of the intelligence community. Note that threat evaluation is not a "hardware matching" process as is commonly supposed, that is, if intelligence indicates that a prospective enemy has, or is able to build a Mach 2.5 aircraft, then we must have one too, but is rather an analysis of the effects of his possessing such an aircraft on the accomplishment of our mission by our aircraft.
This type of analysis gauges the mission, measured against the threat, and permits establishment of the performance levels required to do the job. For our example, attack aircraft, the normal design goal is to maximize the area under the payload-radius curve, that is, to design the aircraft to carry a maximum weight of bombs a maximum distance. Simple, straightforward application of this principle without regard to other factors would produce a very large, heavy aircraft, therefore, we must attempt to establish some reasonable upper limit on the amount of ordnance required. This is difficult to do; in war, one may assume that targets will continue to exist until the enemy has surrendered. Hence, saturation effects do not normally exist. There is no finite number of targets that must be destroyed, so a bomb load within the capability of the aircraft carrier to provide with regularity must be determined. Maximum bomb load per sortie then becomes a matter of judgment, backed by analysis of target application, the various types of weapons available and required, and weapons technology.
Range and radius requirements are more easily handled by the analyst. Disregarding carrier standoff, one can plot cumulative land area as a function of distance from the nearest coast. This can be done world-wide, or for selected areas. An example of such a plot made for 14 selected geographical areas where naval air power may be required, is shown in Figure 1. Such a curve enables the identification of the penetration distance required to eliminate major sanctuaries due to inability to reach them. From this curve, one may deduce that a 600-nautical-mile penetration will enable reaching about 95 per cent of the land area considered. Eighty per cent of this area can be reached with a 400-nautical-mile penetration. Task force standoff distances and mission profiles are other factors which must enter this sort of analysis. Both will depend upon the threat and the general environment. Where the threat permits, carrier bases may operate relatively close to an enemy coast, in other circumstances, it may be desirable to keep standoff at a maximum. Where the threat to our aircraft permits, a high flight profile may be employed to gain extended range. In high threat areas, low level penetration may be required and ranges shortened. Continuing this process, we can thus arrive at standard mission profiles with nominal bomb loads for insertion into the formal aircraft requirement as legitimate, established design goals.
Other aspects of performance can be derived in the same manner. For fighter aircraft, speed requirements are particularly important. These are based not only on the estimated performance of the enemy threat, but also include the types of weapons he has, the types of weapons we have, our respective fire control systems and detection capabilities and other operational factors. If a prospective enemy has a standoff air-to-surface missile capability with a given range, for example, the fighter climb and dash capability required to counter this threat can be calculated, given the typical range at which the enemy will be detected. In either fighter or attack aircraft, a major aspect of performance relates to maneuverability and the ability of the aircraft to pull G's and turn abruptly. This ability, measured against that of an enemy aircraft, provides an index of the results to be expected in a plane-to-plane encounter. Similarly, acceleration time is important in judging the survivability of an aircraft when it is attacked by another.
The derivation of these various factors in this manner results in a statement of the performance factors laid out in logical order. The requirement states that the aircraft must be capable of a given maximum speed and rate of climb, that it must accelerate to that speed in a certain time, that it must be capable of executing certain maneuvers at certain speeds and altitudes, that it must carry certain ordnance loads to specific ranges, that it must have specific navigational and communication capabilities, plus satisfying a host of military specifications regarding such items as airframe strength, pilot visibility, and aerodynamic stability.
At this point in the requirements process, the performance level which has been determined to be necessary or desirable, must be considered against the "state of the art," that which it is technically possible to achieve with an acceptable degree of assurance and economy. This estimate of the state of the art is one of the most difficult portions of the process, and at the same time, one least susceptible to analytical methods. Recognizing the decade lag between concept and hardware, an educated prediction of what can be done in the future is required. If performance goals are accepted that are short of those which may be available, a system of less over-all effectiveness will result. If the state of the art is overreached, we may built systems that are unreliable, cannot be maintained, or just will not work at all. Research is the major tool which indicates the technical capabilities available, a sound management plan includes significant checkpoints or milestones along the way, so that progress may be reasonably confirmed. Too often, if incorporation of new technology in a weapons system is delayed until it can be absolutely assured, it arrives in the hardware stage already obsolete or obsolescent. The man who refused to buy an automobile, because he was "waiting until they were perfected" provides a rough analogy.
With all of these steps accomplished—and the process we have described is actually circular, rather than linear in nature—the aircraft engineer can sit down with the specific operational requirement and design an aircraft. In the requirement statement, certain mission and performance specifics are critical, others less important. For a given aircraft, required engine thrust is generally sized by maximum speed and acceleration requirements. The engine size is thus established and its associated fuel specifics may be estimated. A long-range mission requirement will then permit determination of fuel required and this, in turn, will size the fuselage necessary to house this fuel. Speed and maneuverability requirements will establish the wing area for the aircraft's fuselage and engine combination. Gradually, an aircraft can be constructed on paper which will satisfy the various stated requirements.
For a carrier aircraft, a number of restraints are imposed upon the design by the carrier herself. Maximum aircraft size and weight are set by aircraft elevators, hangar deck clearances, and catapult and arresting gear limits. Take-off and landing speeds and low speed maneuverability have direct effects on the ability of the aircraft to operate from the carrier. Since the carrier deck represents limited real estate available for operating the carrier air wing, aircraft size and shape determine spotting factors and how many aircraft can be brought aboard and operated effectively.
There are other operational factors that must have their impact on aircraft design. Today, in Southeast Asia, a body of empirical data on aircraft vulnerability based on actual attrition experienced by various types of aircraft is becoming available. The whole problem of reducing aircraft vulnerability is a complex one, and these lessons are applied to improve survivability in the future. Many studies were conducted in efforts to determine the point at which the reduction in aircraft vulnerability at higher attack speeds and lower altitudes is compensated by decreased effectiveness due to the problems of target location and successful attack. This problem was a part of the genesis of Joint Task Force TWO at Albuquerque, New Mexico. A series of tests, designed to produce accurate means for evaluating the factors of speed, altitude, and effectiveness, are being conducted by this activity. These test results are applied as they become available.
If weight is disregarded, a given aircraft can be made almost invulnerable to a given level of opposition or weapon. By adding about one ton of armor to the F-4B Phantom II, a "Stormovik" configuration results which reduces the single-pass kill probability of the aircraft to 5 per cent of that of a standard F-4B facing a 7.62-mm. machine gun emplacement. Is this sort of vulnerability reduction worth the additional weight entailed? The multitude of operational problems, decreased performance and weapon loads, higher landing speeds and weights, would seem to indicate that it is not; tradeoffs are examined to make sure.
Aircraft vulnerability can be reduced in other ways than by the addition of armor plating. Avionics devices, attention to reduced size and cross-section, control of infrared emissions, mechanical design, including the number of engines, addition of redundant control systems and the shielding of vital components behind less vital ones, all make contributions. It is important to note that considerations of aircraft maintainability have received increased attention in recent years.* The growing complexity of aircraft and weapons systems has generated greater attention to improved accessibility and maintenance factors. Many of the features which improve accessibility of components and simplicity in servicing are not conducive to the achievement of minimum aircraft vulnerability, so here again, trade-offs must be closely examined to ensure the best compromise is made. Over-all, one of the best ways to increase aircraft survivability is to maximize its effectiveness per sortie, and this remains a major objective in design. The haphazard application of armor to reduce vulnerability to ground fire could be regretted if a serious air threat materializes, when performance again becomes the major criterion that determines survival or loss.
To summarize, the process by which new aircraft are developed for the Navy today is a complex one, which involves the professional knowledge and work of many individuals. It is equipped with many controls and checkpoints to obviate mistakes that might result from reliance on judgment alone. From the front office of the Chief of Naval Operations and the Deputy Chief of Naval Operations (Air) to the small offices in the Air Systems Command, hundreds of hours are expended in the many decisions, small and large, that must be made before a new-series combat aircraft with trained flying and maintenance crews first arrives aboard ship, ready for action. The talent and application of aviation and electronic engineers, the bulk of analytical ability in the Navy research establishment, and the judgment of technically and operationally experienced officers involved, all are brought to bear on the problem.
To complete this recital of the requirements process and the weapons systems it produces, some examination of aircraft which will soon be reaching the Fleet is in order. As a result of a Navy requirement for a highly competent, very sophisticated fighter aircraft, the joint-use TFX (F-111) aircraft was developed to include the Navy air warfare and the Air Force tactical fighter missions in a single aircraft, using two new technological developments, the turbo-fan engine and the variable-sweep wing. The TFX history that led to the parallel F-111A and F-111B aircraft for Air Force and Navy use, is too involved for detailing here. Suffice it to say that it may be indicative of the manner in which increasing system complexity, cost and development time may dictate joint aircraft for many military applications. Successful Air Force employment of the Navy-developed, carrier-based Phantom II has demonstrated the benefits that such a program may provide.
Earlier, modification of the Skyhawk to the conventional weapons role was discussed. In the early 1960s, Navy planners began to seek a follow-on for the A-4 that would employ the new fan jet engines and take advantage of the benefits in range and bomb load that studies indicated would accrue. The result of this selection was the A-7A Corsair II, an out growth of the earlier Crusader fighter. Now entering production, the A-7A will materially increase attack carrier strike capability, both as regards radius of action and magnitude of attack. Possible Air Force use of this aircraft will add further credence to the joint usage, or "commonality" idea, at least, so far as Navy-developed aircraft are concerned.
Continuous study of means to increase air warfare and attack capabilities of the Attack Carrier Air Wing has led to consideration of a multi-mission aircraft, able to perform competently in both the fighter and attack roles. Until recently, such an aircraft was not achievable without unacceptable compromises in performance. At the present time, the demonstrated advantage of the variable-sweep wing, the second generation high-thrust-to-weight ratio turbo-fan engine, breakthroughs in microminiaturized avionics, and new developments in low-drag weapons carriage, make such an aircraft appear technologically feasible. The Navy has pursued this multimission, fighter-attack aircraft, called the VFAX, through the TSOR, PTA, SOR and TDP stages described above, and the VFAX program is now under consideration by officials in the Office of the Secretary of Defense. A product of the pattern detailed, the VFAX proposal is backed by a body of analysis, technical evaluation and professional judgment that exceeds any previous aircraft design. With careful attention to deadlines the proposed VFAX aircraft could be in Fleet service in 1972.
A final caveat may be in order. The methods here detailed have served the nation, and the Navy, extremely well in the past. Navy combatant aircraft equal or better any military aircraft in the world, in any service, and each is the product of the procedures described above. In the interests of complying with fiscal constraints, in seeking the economies to be gained by commonality, and by relying perhaps too heavily on systems analysis versus professional judgment, there is a danger of deferring new developments in favor of extended production of older models, and of reducing new development "starts" to unacceptable minimums. To counter this possible trend, it is necessary that the Navy ensure that requirements are defensible in every reasonable examination. Dedication to the effort to produce requirements with unquestioned validity will continue the production of outstanding Navy aircraft.
A graduate of the U. S. Naval Academy in the Class of 1944, Captain Vito became a naval aviator and served in carrier air groups on board the Princeton, Intrepid, and Forrestal. He was a member of the Armed Forces Special Weapons Project at Albuquerque, New Mexico, and was later assigned to Air Development Squadron FIVE. In 1953, he attended the Naval War College and, subsequently, was Commanding Officer of Attack Squadron EIGHTY-THREE. Operations Officer of COMCARDIV SEVEN from 1963 until 1965, he now heads the Planning Requirements Branch (0P-506) OPNAV.