The Grumman F-14 Tomcat is an American supersonic, twin-engine, two-seat, variable-sweep wing fighter aircraft. The Tomcat was developed for the United States Navy's Naval Fighter Experimental (VFX) program after the collapse of the F-111B project. The F-14 was the first of the American teen-series fighters, which were designed incorporating air combat experience against MiG fighters during the Vietnam War.
Variable-geometry wings and aerodynamic design
F-14 Tomcat with wings showing asymmetric sweep
The F-14's wing sweep can be varied between 20° and 68° in flight, and can be automatically controlled by the Central Air Data Computer, which maintains wing sweep at the optimum lift-to-drag ratio as the Mach number varies; pilots can manually override the system if desired. When parked, the wings can be "overswept" to 75° to overlap the horizontal stabilizers to save deck space aboard carriers. In an emergency, the F-14 can land with the wings fully swept to 68°, although this presents a significant safety hazard due to greatly increased stall speed. Such an aircraft would typically be diverted from an aircraft carrier to a land base if an incident did occur. The F-14 has flown and landed safely with an asymmetrical wing-sweep on an aircraft carrier during testing; this capability could be used in emergencies. The wing pivot points were significantly spaced far apart. This had two benefits. The first was that weaponry could be fitted on a pylon on the fixed wing glove, liberating the wings from having swiveling pylons fitted, a feature which had proven to add significant drag on the F-111B. Since less of the total lifting area was variable, the centre of lift moved less as the wings moved reducing trim drag at high speed. When the wing was swept back, its thickness-to-chord-ratio decreased which allowed the aircraft to satisfy the mach 2.4 top speed required by the U.S. Navy. The body of the aircraft contributed significantly to overall lift and so the Tomcat possessed a lower wing loading than its wing area would suggest. When carrying 4 Phoenix missiles or other heavy stores between the engines this advantage was lost and maneuverability was reduced in those configurations.
Rearview of the F-14 showing the area between the engine nacelles
Ailerons are not fitted, with roll control being provided by wing-mounted spoilers at low speed (which are disabled if the sweep angle exceeds 57°), and by differential operation of the all-moving tailerons at high speed. Full-span slats and flaps are used to increase lift both for landing and combat, with slats being set at 17° for landing and 7° for combat, while flaps are set at 35° for landing and 10° for combat. An air bag filled up the space occupied by the swept-back wing when the wing was in the forward position and a flexible fairing on top of the wing smoothed out the shape transition between the fuselage and top wing area. The twin tail layout helps in maneuvers at high angle of attack (AoA) while reducing the height of the aircraft to fit within the limited roof clearance of hangars aboard aircraft carriers. Two triangular shaped retractable surfaces, called glove vanes, were originally mounted in the forward part of the wing glove, and could be automatically extended by the flight control system at high Mach numbers. They were used to generate additional lift (force) ahead of the aircraft's center of gravity, thus helping to compensate for the nose-down pitching tendencies at supersonic speeds. Automatically deployed at above Mach 1.4, they allowed the F-14 to pull 7.5 g at Mach 2 and could be manually extended with wings swept full aft. They were later disabled, however, owing to their additional weight and complexity. The air brakes consist of top-and-bottom extendable surfaces at the rearmost portion of the fuselage, between the engine nacelles. The bottom surface is split into left and right halves, the tailhook hangs between the two halves, an arrangement sometimes called the "castor tail".
Engines and structure
The F-14 was initially equipped with two Pratt & Whitney TF30 (or JT10A) turbofan engines with each providing a maximum thrust of 20,900 lb (93 kN) and giving the aircraft an official maximum speed of Mach 2.34. The F-14 would normally fly at a cruising speed for reduced fuel consumption, which was important for conducting lengthy patrol missions. Both of the engine's rectangular air intake ramps were equipped with movable ramps and bleed doors to meet the airflow requirements of the engine but prevent dangerous shockwaves from entering. De Laval nozzles were also fitted to the engine's exhaust.
An F-14D prepares to refuel with probe extended
The performance of the TF30 engine became an object of criticism. John Lehman, Secretary of the Navy in the 1980s, told the U.S. Congress that the TF30/F-14 combination was "probably the worst engine/airframe mismatch we have had in years" and that the TF30 was "a terrible engine"; 28% of all F-14 accidents were attributed to the engine. A high frequency of turbine blade failures led to the reinforcement of the entire engine bay to limit damage from such failures. The engines also had proved to be extremely prone to compressor stalls, which could easily result in loss of control, severe yaw oscillations, and could lead to an unrecoverable flat spin. At specific altitudes, exhaust produced by missile launches could cause an engine compressor stall. This led to the development of a bleed system that temporarily blocks the frontal intake ramp and reduces engine power during missile launch. With the TF30, the F-14's overall thrust-to-weight ratio at maximum takeoff weight is around 0.56, considerably less than the F-15A's ratio of 0.85; when fitted with the General Electric F110 engine, an improved thrust-to-weight ratio of 0.73 at maximum weight and 0.88 at normal takeoff weight was achieved. Despite having large differences in thrust, the F-14A, F-14B, and later F-14D with the newer GE F-110 engines were rated at the same top speed.
The wings had a two-spar structure with integral fuel tanks. Around 25% of the structure is made of titanium, including the wing box, wing pivots, and upper and lower wing skins; this is a light, rigid, and strong material and electron beam welding was used in the construction of the titanium parts.
The landing gear was very robust, in order to withstand catapult launches (takeoffs) and recoveries (landings) needed for carrier operations. It comprised a double nosewheel and widely spaced single main wheels. There were no hardpoints on the sweeping parts of the wings, and so all the armament is fitted on the belly between the air intake ramps and on pylons under the wing gloves. Internal fuel capacity is 2,400 US gal (9,100 l): 290 US gal (1,100 l) in each wing, 690 US gal (2,600 l) in a series of tanks aft of the cockpit, and a further 457 US gal (1,730 l) in two feeder tanks. It can carry two 267 US gal (1,010 l) external drop tanks under the engine intake ramps. There is also an air-to-air refueling probe, which folds into the starboard nose.
Avionics and flight controls
The cockpit has two seats, arranged in tandem, outfitted with Martin-Baker GRU-7A rocket-propelled ejection seats, rated from zero altitude and zero airspeed up to 450 knots. The canopy is spacious, and fitted with four mirrors to effectively provide all-round visibility. Only the pilot has flight controls; the flight instruments themselves are of a hybrid analog-digital nature. The cockpit also features a head-up display (HUD) to show primarily navigational information; several other avionics systems such as communications and direction-finders are integrated into the AWG-9 radar's display. A significant feature of the F-14 was its Central Air Data Computer (CADC), designed by Garrett AiResearch, that formed the onboard integrated flight control system. It used a MOSFET-based Large-Scale Integrationchipset, the MP944, making it possibly the first microprocessor in history.
F-14 with landing gear deployed
The aircraft's large nose contains a two-person crew and several bulky avionics systems. The main element is the Hughes AN/AWG-9 X band radar; the antenna is a 36 in (91 cm)-wide planar array, and has integrated Identification friend or foe antennas. The AWG-9 has several search and tracking modes, such as Track while scan (TWS), Range-While-Search (RWS), Pulse-Doppler Single-Target Track (PDSTT), and Jam Angle Track (JAT); a maximum of 24 targets can be tracked simultaneously, and six can be engaged in TWS mode up to around 60 mi (97 km). Cruise missiles are also possible targets with the AWG-9, which can lock onto and track small objects even at low altitudewhen in Pulse-Doppler mode. For the F-14D, the AWG-9 was replaced by the upgraded APG-71 radar. The Joint Tactical Information Distribution System (JTIDS)/Link 16 for data communications was added later on.
The F-14 also features electronic countermeasures (ECM) and radar warning receiver (RWR) systems, chaff/flare dispensers, fighter-to-fighter data link, and a precise inertial navigation system. The early navigation system was inertial-based, point-of-origin coordinates were programmed into a navigation computer and gyroscopes would track the aircraft's every motion to calculate distance and direction from that starting point. Global Positioning Systemlater was integrated to provide more precise navigation and redundancy in case either system failed. The chaff/flare dispensers were located on the underside of the fuselage and on the tail. The RWR system consisted of several antennas on the aircraft's fuselage, which could roughly calculate both direction and distance of enemy radar users; it could also differentiate between search radar, tracking radar, and missile-homing radar.
Featured in the sensor suite was the AN/ALR-23, an Infra-red search and track sensor using indium antimonide detectors, mounted under the nose; however this was replaced by an optical system, Northrop's AAX-1, also designated TCS (TV Camera Set). The AAX-1 helped pilots visually identify and track aircraft, up to a range of 60 miles (97 km) for large aircraft. The radar and the AAX-1 were linked, allowing the one detector to follow the direction of the other. A dual infrared/optical detection system was adopted on the later F-14D.