One Hundred Years of U.S. Navy Air Power

by Smith, Douglas V.

  By the mid-1970s, another leap in engine, aerodynamics, and systems technology was in the works. The Air Force Light Weight Fighter Program spawned two competitive designs, the YF-16 and YF-17, which were revolutionary. The Air Force selected the F-16, and eventually Congress directed the Navy to use one of these aircraft as the replacement for its aging A-7 Corsair. It chose the Northrup YF-17 and developed it into the F-18 Hornet. The Hornet is characterized by the extensive application of digital computer technology that results in fly-by-wire control systems in which the pilot’s control inputs are fed to a computer that calculates actual control surface movements, highly capable radars, and refined digital cockpit displays. The F-18 is also highly maneuverable as well as capable of supersonic speeds.

  Echelon VI: The Last Manned Fighters?

  We now enter the future. New aircraft such as the Air Force’s F-22 Raptor and the F-35 Joint Strike Fighter (now called the Lightning II) bring even more advanced capabilities and characteristics to the air combat arena. These include a high degree of stealthiness, major increases in on-board data processing, as well as huge increases in sensing and communications capacity. These aircraft will be flying network nodes as well as highly lethal fighters. They will be supersonic, but their top-end speeds will be no higher and in some cases less than earlier generation machines because such high speeds are not considered a worthwhile tradeoff for maneuverability, stealth, and systems capacity.

  Although this chapter is a history of naval aviation’s transition to jet aircraft, it is worthwhile to look even further ahead. Although to some degree speculative, the outlines of a future echelon of Navy carrier aircraft is becoming increasingly clear: they will be unmanned. Emerging control technology based on artificial intelligence is already producing an array of unmanned drones that have proven useful and effective in current wars in Iraq and Afghanistan as well as in other operations around the world. There are a number of reasons for the Navy to develop a new generation of what are termed “Unmanned Combat Aerial Systems” or UCAS. Freed of the requirement to house humans aboard, these aircraft will have even greater stealth and huge increases in range and endurance. If, as seems probable at this point, missiles will dominate all arenas of naval warfare, UCAS will not need to dogfight like traditional manned fighters.

  DEAD ENDS: SEAPLANES AND VERTICAL TAKEOFF AND LANDING

  From the Sea

  For much of its early history the Navy made extensive use of seaplanes, either utilizing floats fitted to aircraft that were otherwise designed for land use, and true flying boats. By the late 1930s, the Navy had abandoned the idea of floatplane fighters and instead used the type as scouts operating from battleships and cruisers. After World War II, the Navy again revived its interest in sea-based fighters, this time swept-wing jets, thinking that swept-winged fighters might not be suitable for carrier operations. It let a contract in 1951 with Convair to produce a delta-winged, supersonic fighter called the Sea Dart. A small flying boat that floated on its fuselage, it used an extendable “hydro ski” to handle the forces of takeoff and landing. Several Sea Darts flew, but their performance was disappointing due to deficient engine thrust. However one did exceed Mach 1 in a shallow dive on a test flight, becoming the only seaplane to break the sound barrier. After several catastrophic accidents, and with the development of carrier-capable swept-wing jets, the Sea Dart project was abandoned.

  The Navy had far more success with larger flying boats. Its PBY Catalina series was used extensively in World War II as a scout and for transport to areas with no airfields. Larger flying boats were put into operation after the war as anti-submarine patrol planes and transports. The idea for a large, jet-powered seaplane emerged from the inter-Service rivalry of the late 1940s and early 1950s with the Air Force, in which the large aircraft carrier United States was cancelled. Seeking to establish its own nuclear strike capability using jet seaplanes, the Navy issued a requirement in 1951, which Martin Aircraft Company eventually won. The result was the P6M SeaMaster, a four-engined, swept-winged aircraft that was to be capable of carrying 30,000 pounds of ordnance on a combat radius of 1,500 miles. It was to be capable of a 0.9-Mach attack speed at sea level. As with the Sea Dart, the SeaMaster showed early promise, with its first flight in 1955, but two catastrophic accidents precipitated a significant redesign. By the time the second model was ready for testing in 1959, the incipient introduction of the Polaris ballistic missile submarine and defense budget cuts resulted in the demise of the program.

  Going Vertical

  The Navy has always had an interest in aircraft that could take off and/or land vertically. Helicopters are ubiquitous and serve the Navy in many ways, but they are not capable of replacing conventional fighter and attack aircraft. Early in the jet era, the Navy experimented with several types of turboprop vertical takeoff and landing (VTOL) aircraft including the XFY-1 Pogo. None of the early turbojet engines had enough thrust to lift an aircraft vertically, nor was there sufficient technology to design a machine that would be controllable in the shipboard environment. The attractions of vertical takeoff and landing are many for the Navy. Without having to worry about catapults and arresting gear, an aircraft carrier could operate significantly more aircraft for a given size, and construction expenses would be less. Moreover, freed from the many safety restrictions and the intricate ballet of on-deck aircraft movements that confine the operations of an aircraft carrier to cycles of an hour and thirty minutes—more or less—a VTOL-equipped carrier would have far greater operational flexibility and rapid response to changing tactical situations.

  However, the price for vertical flight has been too high. The British-designed AV-8 Harrier was the first and most successful “jump jet,” and was the difference between victory and defeat in their Falklands War with Argentina. It also became a workhorse for the U.S. Marine Corps, operating from the decks of catapult-less amphibious ships and austere expeditionary airfields. However, the Harrier has relatively little payload and range. The Navy has passed up this jet because it could not be used as a fleet defense fighter or as a practical attack aircraft, given the mostly long-range missions the Navy has envisioned for its bombers. Even today, with a short takeoff/vertical landing version of the new, fifth-generation Joint Strike Fighter due to be introduced, the Navy is sticking with a conventional catapulted takeoff and arrested landing version. It seems that the Navy may never realize the dream of vertical flight for its tactical aircraft.

  LIVING THE TRANSITION

  As the Navy proceeded into the jet age, it fielded in rapid succession a number of different designs, each representing a significant advance in speed and capability. Some of the early models only had an operational career of two or three years before being superseded by a more advanced design. Many things were changing rapidly in the early 1950s, including ship design and airwing composition. The catastrophic accident rates were due in part to this turbulence—pilots would transition from type to type without adequate training. Some of these jets, like the F9F-2 Panther and F4D Skyray, were relatively easy to handle and bring aboard the carrier, while others such as the F7U Cutlass and the F-8 Crusader were notorious for their difficult handling characteristics. All suffered from engine and system reliability problems, and the advent of more challenging missions, such as night and all-weather operations, exacerbated vulnerabilities inherent in the aircraft and the naval aviation culture.

  Each succeeding echelon of Navy jets represented an improvement over the last. However, echelons II through IV shared a set of design problems that were not substantially overcome until the advent of the F-18. Low thrust and unreliable engines, adverse handling characteristics, especially in the carrier landing approach, and complex man-machine interfaces made flying Navy jets a dangerous business. Military jet flying is loaded with challenges including dogfighting, dive-bombing and formation flying; design defects and difficulties added to the challenges and exacted a frequently fatal price for any deficiencies in aircrew technique. The following sections
provide some insight into the challenges of dealing with the characteristics of Navy jets.

  Handling

  We will start with the handling characteristics of a swept-wing jet. Anyone who has ever piloted an airplane knows that as airspeed decreases, there comes a point at which the wings can no longer sustain flight. In primary training, at a safe altitude the instructor has the student reduce power and hold altitude by easing back on the control stick until the airplane is pitched up at such an angle relative to the oncoming air that the airflow over the wings cannot flow smoothly over the top, and lift is lost. This is termed a stall. In straight-wing airplanes, this stall happens abruptly because the whole wing loses lift at the same time (although most designs have a bit of “twist” put in the wing shape to ensure the stall starts at the wing root near the fuselage and propagates outward, contributing to keeping the wings level in a stall). A swept wing does no such thing. It loses lift more gradually. Moreover, as the jet’s angle of attack increases to compensate for the loss of lift, the wings generate large amounts of induced drag, the air resistance incurred by generating lift. As airspeed slows, lift decreases and induced drag increases, and the swept-wing jet, regardless of how powerful the engines are, can get into a predicament in which it has a high rate of sink but is not fully stalled, and full power cannot get it out of it. The only way out is to drop the nose of the aircraft, at which point the jet drops like a rock until flying speed is regained. If the jet is near the ground, like in a landing pattern, it is doomed.

  As the Navy started introducing swept-wing jets, pilots who were used to the characteristics of straight-wing machines could get themselves into a terminal situation because their habit pattern would cause them to pull up on the nose to control rate of descent rather than add power. If they were slow in recognizing the developing problem, they would find themselves in a high rate of descent near the ground that they could not get out of. Early ejection seats could not handle high rates of descent near the ground. The end result was a lost jet and dead pilot. This was an all-too-common occurrence throughout the early jet era. Of course, this characteristic was exacerbated in the aircraft carrier operating environment. Swept-wing aircraft have higher approach and landing speeds than straight-wing aircraft, and they must be operated much nearer to stall speed to keep arrested landing speeds down and reduce the risk of damage on landing. Stalling and crashing in the landing pattern was a definite occupational hazard for Navy jet pilots. Even as late as the early 1990s, crashes of this sort were occurring in the A-7 and F-14 communities.

  However, gradual stall was not the only adverse handling characteristic of swept-wing jets. Each particular model had its own idiosyncrasies that could lead to loss of control. The F-14 had a flat spin mode that could be entered if the pilot pulled too hard in a slow speed dogfight, which was frequently unrecoverable. The A-7 had a rather violent way of departing from controlled flight at high speeds that would result in an “auger,” a high-speed roll heading straight down. Early A-7 pilots interpreted the auger as a spin (a slow speed stalled and twirling condition) and put in anti-spin controls that only made the situation worse. A number of Corsair drivers flew into the ground at six hundred knots trying to get out of what they thought was a spin. It took several fatalities until the accident boards finally figured out what had happened, and ordered additional training instituted for pilots to recognize and recover from the condition. This is typical of what happened in some form for almost every new jet design the Navy introduced during the transition period. All tactical jet crews engaged in dogfight training, a demanding environment in which it is necessary to fly the airplane to the limits of its capability, especially in the slow speed realm. A steady stream of lost aircraft progressively taught the Navy and the aircraft designers about the deficiencies of each design, some of which did not come to light until years after the aircraft’s introduction. Aircrews were only too aware of the dangers, but there was a special pride in being able to master a hard-to-fly jet. There was a picture of a Marine Corps F-4 Phantom that hung for many years behind the bar at the Naval Air Station in Fallon, Nevada. On the matting was an inscription that said: “If it don’t buck, there ain’t no rodeo.”

  Engines

  Stepping on the gas of a car yields instant response—the same as when a pilot moves the throttle forward on a propeller-driven airplane. This is because the increased gas flow to the cylinders causes bigger explosions and moves the pistons faster right away. Not so in a jet engine. Increasing the fuel flow causes a hotter fire and higher pressures to be generated in the combustion chambers, but this high-pressure gas must now travel aft to the turbine section and cause it, and the attached compressor section up front, to spin a bit faster. This faster spin compresses the incoming air more, which in turn generates higher pressures in the combustors, which then cause the turbine to spin faster, and so on. Obviously, this takes a finite amount of time. The heavier the compressor and turbine assembly, the more inertia it has, and the more time required to spin up and get to full power. Early jet engines had heavy rotating cores and lower operating temperatures due to less advanced metallurgy, so the lag time between the pilot putting the power lever forward and full thrust being produced was significant. Slow engine response, coupled with the difficult slow-speed approach and landing characteristics of swept wings, produced a lethal combination for Navy pilots. Some early jets such as the Panther and Cougar had centrifugal flow jet engines in which the compressor sent air outward instead of straight back. A centrifugal flow compressor was heavier and less efficient than an axial flow one, and thus increased engine lag even more.

  However, jet engine spool-up lag was only half of the problem; engines also lagged in spooling down when the pilot pulled back on the throttle. In piston-engined propeller aircraft, not only did the engine immediately stop putting out power, the propeller acted as a kind of speed brake. Thus, on the straight deck carriers, the Landing Signal Officer (LSO) would give a “cut” signal when the aircraft had the deck made, and the prop plane would settle into the wires. If, for some reason, the hook did not engage the wires, there was a barrier set up to snag the landing gear and stop the plane before it ran into the aircraft parked on the forward part of the flight deck. This system did not work well for jets. Engine lag tends to bedevil student pilots when they first attempt to fly a jet straight and level, causing over-controlling and a rather sinusoidal flight path until they get the hang of leading the power, both in adding it and reducing it. Combined with the lack of a robust and disciplined transition program from propeller aircraft, which was precisely the case in the late 1940s and early 1950s, jet engine lag set the stage for disaster aboard straight deck aircraft carriers. The straight-winged jets such as the Banshee and Panther tended to “float” anyway, the wings continuing to generate lift even when the aircraft speed was just above stall. As a result, if a pilot added too much power in close to the carrier on the final few seconds of an approach, say, to compensate for going below glidepath (remember, the pilot probably added a little power and got no instant response like in a prop, and so added more), then realized he had over-corrected and pulled the power to idle on the LSO’s cut signal, the engine would continue to pump out some residual thrust as it spooled down and the jet would level off (float, especially as it got instantly into the “ground effect” of the carrier’s flight deck) and not only miss the wires, but also the mid-ship barriers. Most of the time there were many aircraft parked up on the bow, protected, in theory, by the barriers. The result was a catastrophe in which the floating jet ploughed into the parked machines. This happened more than once. Even with improved jet engines, problems with residual thrust did not entirely disappear, but the arrival of the angled flight deck turned potential catastrophes into harmless “bolters” in which the jet simply continued off the angle and into the air to try again.

  As metallurgy and jet engine design improved, response lag was reduced. The J-79 turbojet that powered the F-4 Phantom had very quick respon
se and pilots loved it. Moreover, it proved to be highly reliable. However, a trend developed in the 1960s to place fan jet engines in tactical jets. A fan jet engine has a greater diameter compressor section so that some of the compressed air bypasses the “hot section” of the engine and flows directly out the tailpipe. This adds efficiency to the engine, giving the airplane better “mileage.” For tactical jets, which always lack space for fuel, increased mileage means greater radius of action; a good thing generally. However, there was a price to be paid. Fan jets originated in the airline industry, where the engines are treated tenderly, being brought to full power gradually and left unmolested at cruising power for most of the flight. Not so with fighters. The requirements of combat and carrier landing demand constant and rapid throttle movements. Obviously, the addition of a fan section adds weight to the rotating core, so it is easy to imagine the impact on throttle response times. Moreover, the constant stress of having to accelerate that heavy fan imposes much greater stress on the turbine section. Sure enough, Navy fighters and attack aircraft equipped with fan jets started suffering high rates of engine failure. This was bad enough in a two-engine F-14, but catastrophic in the single-engine A-7 Corsair. At one point, the Navy made Corsair pilots limit their throttle movements so the temperatures on the turbine blades could be controlled. In addition, the engines were being preemptively replaced every two hundred hours of operation. Even with these restrictions Corsairs were falling out of the sky. The TF-30 engine, which powered both the early A-7 models and the F-14, also had a tendency to develop compressor stalls, where the airflow through the compressor burbles, like in a wing stall. The engine bangs like crazy and loses power. Many jets were lost to such stalls.