F-16 Evolution
By Eric Hehs Posted 19 February 2014
All F-16s are not created equal. Fighting Falcons rolling out of the factory today are nothing like earlier versions. Some differences are visible—larger control surfaces; wider inlet; tinted canopy; squared landing lights; and various antennas, vents, bumps, and blisters. Most differences require more than the naked eye to see—structural beef-ups, improved engines, digital electronics, vastly increased computing capacity, and software changes to accommodate new functions, sensors, and weapons.
The all-glass cockpit (no mechanical gauges) of the latest F-16s is the manifestation of many of these improvements. Three large five- by seven-inch color multifunction displays transmit information from a variety of sensors to the pilot in straightforward color graphics. The cockpit features hands-on throttle and side-stick switch controls, night vision goggles-compatible lighting, a color moving map, and a large head-up display. A helmet-mounted cueing system allows pilots to target weapons by simply turning their heads.
Beginnings
The original F-16 was designed as a lightweight air-to-air day fighter. Air-to-ground missions immediately transformed the first production F-16s into multirole fighters. The F-16s that followed expanded and refined these roles with beyond-visual-range missiles, infrared sensors, precision-guided munitions, and many other capabilities. Current and planned versions of the F-16 build on these refinements, enhancing capabilities even further.
But the fundamental strengths of the original design remain. At the heart of every Fighting Falcon is the lightweight fighter concept championed by Col. John Boyd and the other members of what came to be known as the Lightweight Fighter Mafia in the US Air Force and Department of Defense. This group favored simple and small fighter designs that could change direction and speed faster than their potential adversaries—designs that were harder to detect; designs that were inexpensive to produce, operate, and maintain. The Fighter Mafia advocated using technology to increase effectiveness or reduce cost. They went so far as to question and thoroughly analyze the basic assumptions of how fighters were judged and compared.
Engineers in Fort Worth transformed these ideas into reality in the 1970s. The resulting lightweight fighter combined a host of advanced technologies that had never been used in operational fighters. A blended wing-body, variable camber wings, and forebody strakes provided extra lift and control. Fly-by-wire flight controls improved response time and replaced heavy hydro-mechanical systems with lighter and smaller electronic systems. Relaxed static stability, made possible by the fly-by-wire system, greatly enhanced agility and stability. A side-mounted throttle and stick, head-up display, thirty-degree seat back angle, hands-on controls, and bubble canopy improved the pilot’s g-tolerance and situational awareness.
All of these technologies had been explored before in a variety of other aircraft and research programs. But the F-16 prototype, or YF-16, was the first airplane to incorporate all of them into a producible design.
The development of the YF-16 optimized a design for performance. The evolution of the production F-16s, on the other hand, became a balancing act between adding and improving capabilities and maintaining the original design’s optimized performance.
Capability improvements can take many forms: countermeasures, infrared sensors, laser targeting devices, missionized rear cockpits, dorsal fairings, datalinks, satellite communications, helmet-mounted cueing systems, conformal fuel tanks, large color displays, all-glass cockpits, improved stores (reconnaissance pods, weapons, and other wing-mounted systems), and auto-recovery systems. Each new capability benefits from its own evolutionary process. All of these improvement leaps are packed into an airframe still capable of sustaining nine g’s and of out-performing other fourth-generation fighters.
Pratt & Whitney and General Electric have added to the evolution with impressive improvements in engine performance. The original Pratt & Whitney engine on the YF-16 developed about 23,000 pounds of thrust. The engines on the Block 50/52 aircraft develop nearly 30,000 pounds of thrust. The GE F110-GE-132 engine on the Block 60 F-16 is rated at 32,500 pounds of thrust. So, even though the F-16’s overall weight has increased, its thrust-to-weight ratio has improved as well.
However, the Lightweight Fighter Mafia will point out that thrust-to-weight ratio is not the only indicator of aircraft performance. The figure doesn’t account for the effects of wing loading and aerodynamic drag. A better measure of performance is energy rate (or Ps), which is a function of thrust, weight, velocity, and drag. Every external payload extracts a performance price in aerodynamic drag. And F-16s rarely fly without a few stores hanging under the wing.
Technology comes to the rescue again. Advances in electronic miniaturization have resulted in lighter, more compact hardware that, in turn, significantly reduces drag. The latest navigation and targeting pods, for example, are smaller, lighter, and aerodynamically cleaner than first-generation pods. Electronic countermeasure systems have shrunk, too, and have more recently found their way under the F-16’s skin, eliminating even more drag. Weaponeers are making bombs and missiles smaller, lighter, and more streamlined. Drag reductions have often accompanied efforts to add more systems and weapons to the airplane and to make the airplane less detectible and more survivable.
While the F-16 today benefits from the electronic revolution, the original designers did not anticipate it. In fact, they purposely kept the aircraft as dense as possible to prevent additional systems—and the extra weight they would bring—from being placed inside the airframe. Technology advances have allowed much more capability to be packed into that same space or, in some cases, in much less space.
Building Blocks
Keeping up with all the varieties of the F-16 is no small task. The job is simplified, though, because most changes to the F-16 are made in groups, or blocks, to track items on the production line. Whenever a new-production configuration for the F-16 is established, the block number increases.
The first production aircraft following the two YF prototypes and the eight full-scale development F-16s were Blocks 1 and 5. (From Block 30/32 on, a major block designation ending in 0 signifies a General Electric engine; one ending in 2 signifies a Pratt & Whitney engine.) The current highest operational block designation, however, is Block 60, which is flown by the United Arab Emirates.
Significant modification programs have their own designation as well such as the Mid-Life Upgrade and the Common Configuration Improvement Program. The latest proposed significant modification for the F-16 is called the F-16V (V standing for Viper).
The A in F-16A refers to Blocks 1 through 20 single-seat aircraft. The B in F-16B refers to the two-seat version. The letters C and D were substituted for A and B, respectively, beginning with Block 25. The new series letters emphasize the major differences occurring between Blocks 15 and 25. Block 60 denotes the transition from the F-16C/D to the F-16E/F.
Full-Scale Development: Production Predecessors
The YF-16 was chosen over the YF-17 in the Lightweight Fighter competition in 1975. Work began on the first of eight full-scale development, or FSD, F-16s, incorporating the first major—mostly internal—design changes. The designers were intent on retaining the outstanding flying qualities of the original design. So no changes that would degrade the prototype’s aerodynamics were made. At the same time, they had to adapt the airplane to amplified air-to-ground requirements. The overall length grew by thirteen inches. The nose acquired a slight droop to accommodate the Westinghouse APG-66 multimode radar.
To respond to the need for larger air-to-ground payloads, the wing and tail surfaces were enlarged to carry the extra weight. The wing area grew from 280 to 300 square feet, which is about as much as it could grow without requiring additional internal bulkheads to lengthen the fuselage. The horizontal tails and ventral fins grew about fifteen percent. The flaperons and speed brakes grew by about ten percent. An additional hardpoint was placed under each wing, giving the aircraft a total of nine. The airframe was also structurally strengthened.
Other changes in the FSD aircraft included a lighter weight Stencel SIIIS ejection seat, a simpler single door instead of twin doors on the nose landing gear well, and a self-contained engine starter. The canopy transparency was strengthened to withstand a four-pound, 350-knot bird strike. The radome was hinged to ease access to the radar.
The YF-16 validated the aerodynamics, propulsion, and handling qualities of the aircraft’s basic design. With the major design issues out of the way, engineers concentrated more on internal details—such as the electrical system, hydraulics, and avionics—with the FSD aircraft. The FSD aircraft had no block numbers, though they are often referred to as Block 0 F-16s.
Blocks 1 And 5: Going Operational
After the prototype and FSD programs, the first Block 1 F-16 (serial number 78-0001) was flown for the first time in August 1978 and delivered to the US Air Force that same month. The aircraft was first assigned to the 388th Tactical Fighter Wing at Hill AFB, Utah, and later became an interceptor with the 125th Fighter Interceptor Group in Jacksonville, Florida, followed by a tour at the 158th Fighter Interceptor Group in Burlington, Vermont. It then was flown by the 127th Tactical Fighter Wing at Selfridge Air National Guard Base, Michigan. The aircraft was eventually sent to Lowry AFB, Colorado, as a student trainer. The first operational F-16 is now on display at Langley AFB, Virginia.
Ninety-four Block 1 and 197 Block 5 F-16s were manufactured through 1981 for the US Air Force and four European Participating Air Forces. Most Block 1 and Block 5 aircraft were upgraded in 1982 to a Block 10 standard through a program called Pacer Loft. New-production Block 10 aircraft (312 total) were built through 1980. The differences between these early F-16 versions are relatively minor. All production F-16s beginning with Block 1 were outfitted with ACES II ejection seats.
A word about nicknames: Tactical Air Command, now Air Combat Command, officially christened the F-16A as the Fighting Falcon. But that name never found wide use on the flightline. As with many aircraft, the unofficial nickname the pilots pinned on the F-16 did catch on: Viper.
Block 15: Most Produced
The 330th production F-16 was the first of 983 Block 15 aircraft manufactured in five countries and subsequently assembled on three production lines (Fort Worth, Belgium, and Netherlands). The production of the Block 15 spanned fourteen years. Of the more than 4,500 F-16s manufactured to date, Block 15 aircraft are the most numerous, and many of them are still flying today in air forces around the world.
The transition from Block 10 to Block 15 resulted in two hardpoints added to the inlet chin and designated as stations 5R and 5L. The nearly thirty percent larger horizontal tail is the most noticeable difference between Block 15 and previous F-16 versions. The larger tail offset the shift in center of gravity brought on by the weight of the sensors and structures of the two chin hardpoints. The larger tail also provides better stability and control authority, especially at higher angles of attack.
Block 15 aircraft received an operational capability upgrade, or OCU, beginning in 1988. The upgrade added a data transfer unit and a radar altimeter. The radar was improved, and the fire control and stores control computers were expanded. OCU also allowed Block 15 aircraft to fire the AGM-119 Penguin anti-ship, the AGM-65 Maverick air-to-ground, and the AIM-120 Advanced Medium Range Air-to-Air Missile, or AMRAAM. The Block 15 aircraft built from 1988 had OCU, a larger wide-angle head-up display, and the Pratt & Whitney F100-PW-220 engine. Fifteen air arms fly Block 15 aircraft today, including the US Navy.
The Air Defense F-16 is a variant of the Block 15 OCU F-16 equipped with additional systems for the air-to-air role. It has improved APG-66A radar, an APX-109 identification friend or foe interrogator, ARC-200 high-frequency radio, and a 150,000-candlepower spotlight mounted on the left side of the forward fuselage. In the late 1980s and early 1990s, 271 Block 15 airframes were converted to the Air Defense configuration. The first converted aircraft were delivered in early 1989. All of the aircraft initially went to the Air National Guard. The Guard stopped flying the Air Defense version of the F-16 in 2007. Air Defense F-16s are still flown by Jordan and Thailand.
Block 25: From A To C
The Block 25 aircraft marks the evolution from the F-16A/B to the F-16C/D. Block 25 enabled the F-16 to carry AMRAAM as a baseline weapon as well as carrying night/precision ground-attack capabilities. An improved fire control computer, an improved stores management computer, and an inertial navigation system were added along with multifunction displays, new data transfer unit, radar altimeter, and anti-jam UHF radio.
The Block 25 F-16 also received the improved Westinghouse (now Northrop Grumman) AN/APG-68 radar, which offered increased range, better resolution, and more operating modes. Block 25 featured new upfront controls, a larger head-up display, and two head-down multifunction displays. All Block 25s were originally powered by the Pratt & Whitney F100-PW-200, but the engines have since been upgraded to the -220E configuration. The first of 244 Block 25 F-16s flew in June 1984. Block 25 is the only F-16 to be employed exclusively by the US Air Force.
Block 30/32: New Engine Choices
Block 30/32 added two new engines to the F-16 line—the Pratt & Whitney F100-PW-220 and the General Electric F110-GE-100. The aircraft’s engine bays are common to both engines by design. A larger inlet was introduced at Block 30D for the GE-powered F-16s, which are often called big-mouth F-16s. The larger inlet, formally called the modular common inlet duct, allows the GE engine to produce its full thrust at lower airspeeds.
The smaller inlet, called a normal shock inlet, has not changed for the -220 and subsequent Pratt & Whitney engines. A Pratt & Whitney F100-PW-229 engine powered the Variable Inflight Stability Test Aircraft, or VISTA/F-16, which featured the larger inlet. This is the only F-16 with a large inlet and a Pratt & Whitney engine.
Block 30/32 can carry AGM-88A high-speed anti-radiation missiles, or HARM. Like the Block 25, it can carry the AGM-65 Maverick missile. Changes at Block 30D allowed the aircraft to carry twice as many chaff/flare dispensers for self-protection, and the forward radar warning receiver antennas were relocated to the leading-edge flap. These beer can-shaped antennas have since been retrofitted onto all previous F-16C/D aircraft. Block 30/32 has a crash-survivable flight data recorder, voice message unit, and expanded memory for the multifunction displays. The first of 733 Block 30/32 F-16s was delivered in July 1987; the airplane was manufactured through 1989.
The F-16N manufactured for the US Navy was a Block 30 variant. It was powered by the GE F110-GE-100 engine and had the small inlet associated with early Block 30 production. The F-16N also carried the APG-66 radar of the F-16A models and minor structural differences for meeting Navy requirements. The aircraft had no internal 20-mm gun. Twenty-two F-16Ns and four TF-16Ns (two-seaters) were built from 1987 to 1988. They were used for dissimilar air-to-air training with three Navy adversary squadrons and at the Navy’s Fighter Weapons School (Top Gun) until 1994.
The US Navy once again began flying Fighting Falcons in early 2002 when the first of ten single-seat and four two-seat Block 15 F-16s were delivered to NAS Fallon in Nevada (the current home of Top Gun). These aircraft, with distinctive paint schemes, are low-hour F-16A/Bs that had been in storage.
Block 40/42 Night/Precision Attack
With Block 40/42, the F-16 gained capabilities for navigation and precision attack at night and in all weather conditions and traded its original analog flight controls for a digital system and new core avionics.
The landing gear of Block 40/42 was beefed up and extended to handle the Low Altitude Navigation and Targeting Infrared for Night, or LANTIRN, targeting and navigation pods and more extensive air-to-ground loads. By design, the landing gear bay doors bulge slightly to handle the larger wheels and tires. The LANTIRN pods also necessitated moving the landing lights from the struts of the main landing gear to the leading inside edge of the nose gear door. The larger wide angle collimating, or WAC, head-up display was needed for LANTIRN as well. This wide-angle raster HUD, as it is called, is capable of displaying the infrared image from the LANTIRN navigation pod used in low-altitude night navigation.
The precision weapons incorporated by Block 40/42 include the GBU-10, GBU-12, and GBU-24 Paveway family of laser-guided bombs as well as the GBU-15 glide bomb.
Block 40/42 also featured the addition of the APG-68(V5) radar, automatic terrain following (part of the LANTIRN system), global positioning system, full provisions for internal electronic countermeasures, an enhanced-envelope gun sight, and a capability for bombing moving targets.
Production of Block 40/42 began in 1988 and ran through 1995. Twenty-one more Block 40s were built for Egypt, and ten single-seat Block 40s were built for Bahrain during 1999 to 2000.
US Air Force Block 40 aircraft are now equipped and flying missions with night vision goggles and with a datalink system. This system receives highly accurate position information from a forward air controller on the ground. The system then inputs the data into the weapon system computer and displays it as a waypoint on the head-up display.
Block 20 And MLU
Block 20 refers to new-production F-16As that incorporate significant avionic enhancements, including a modular mission computer, or MMC, replacing three other computers. The processing speed of the computer is more than 740 times faster than the computer in the original F-16. It has more than 180 times the memory. An improved radar, the APG-66(V2), features increased detection and tracking ranges and the ability to track more targets.
The Mid-Life Update program, or MLU, refers to the 300 retrofitted Block 15 F-16A/B Belgian, Danish, Dutch, and Norwegian aircraft. These aircraft were also structurally upgraded to meet an 8,000-hour airframe life span in a program called Falcon UP (for unos programmum).
Block 20 and MLU F-16s have wide-angle head-up displays, color multifunction cockpit displays, upfront controls (a set of programmable pushbuttons placed just below the head-up display), a Block 50-style side stick and throttle, ring laser inertial navigation systems, miniaturized global positioning system receivers, digital terrain systems, improved data modems, and advanced interrogators for identifying friendly or foe aircraft. The lighting in the cockpit is compatible with night-vision systems. The aircraft also have provisions for microwave landing systems and helmet-mounted displays.
Block 50/52 Wild Weasel Plus
The first Block 50/52 was delivered to the US Air Force in 1991. The Block 50/52 F-16 is recognized for its ability to carry the AGM-88 HARM in the suppression of enemy air defenses, or SEAD, missions. The F-16 can carry as many as four HARMs.
An avionics launcher interface computer allows the F-16 to launch the HARM missile. US Air Force F-16s have been upgraded to carry the HARM Targeting System, or HTS, pod on the left intake hardpoint so it can be combined with laser targeting pods designed to fit on the right intake hardpoint. The HTS pod contains a hypersensitive receiver that detects, classifies, and ranges threats and passes the information to the HARM and to the cockpit displays. With the targeting system, the F-16 has full autonomous HARM capability.
The Block 50/52 F-16 continued to be improved, and the current aircraft sold to the FMS customers is equipped with the APG-68(V9) radar, which offers longer range detection against air targets and higher reliability. The Block 50/52 now includes embedded global positioning system/inertial navigation system, a larger capacity data transfer cartridge, a digital terrain system data transfer cartridge, a cockpit compatible with night vision systems, an improved data modem, an ALR-56M advanced radar warning receiver, an ALE-47 threat-adaptive countermeasure system, and an advanced interrogator for identifying friendly aircraft.
In the cockpit, an upgraded programmable display generator has four times the memory and seven times the processor speed of the system it replaces. New VHF/FM antennas increase reception ranges. The Block 50/52 is powered by increased performance engines—the General Electric F110-GE-129 and the Pratt & Whitney F100-PW-229—each rated to deliver over 29,000 pounds of thrust in afterburner. Block 50/52 are the first F-16 versions to fully integrate the AGM-84 Harpoon anti-shipping missile.
New-production Block 50/52 aircraft ordered after 1996 include color multifunction displays, the modular mission computer, and a multichannel video recorder. All international versions of the Block 50/52 have LANTIRN capability.
More than 800 Block 50/52s have been delivered from production lines in Fort Worth, Korea, and Turkey. The Fort Worth production line is currently the only active F-16 line. The other production lines have completed their production runs and have been shut down.
Engines
The engines that power the F-16 have improved in more ways than in maximum thrust. Engines used in early F-16s required from six to eight seconds to spool up from idle to afterburner. Since then, electronic controls have replaced hydro-mechanical systems. The changes allow current engines to go from idle to full afterburner in two seconds. Engine reliability and ease of maintenance have also been improved significantly. Today’s F-16 engines can be expected to deliver eight to ten years of operational service between depot inspections.
Digital engine controls, first introduced on Pratt & Whitney-powered F-16s in 1986, have also improved performance. Older hydro-mechanical controls had to be trimmed to operate at the most challenging point within the F-16’s flight envelope. Digital engine controls automatically adjust to the operating environment, so that they optimize engine performance at all points within the flight envelope. All engines being built today for the F-16 have digital engine controls.
Commonality
With all the varieties of the F-16 produced through the years, the US Air Force decided to standardize its F-16 fleet to simplify logistics, maintenance, and training. The service, building on the success of the MLU program, implemented the Common Configuration Implementation Program (CCIP) in 1997 to bring all of the Block 40/42/50/52 into a common avionics configuration.
The CCIP added color displays, common missile warning systems, and an improved modular mission computer to Block 40/42 and Block 50/52 F-16s as well as an advanced datalink, called Link-16, that is standard for US and NATO aircraft. The upgrade also included the multi-service standard joint helmet-mounted cueing system (JHMCS). This system works with the high-off-boresight AIM-9X air-to-air missile as well as with other slewable sensors and provides the pilot with other situational awareness and navigation data without looking in the cockpit. More than 200 Block 50/52 and 420 Block 40/42 aircraft were involved in the program. The Air National Guard (ANG), Air Force Reserve Command (AFRC), and active duty Air Force units are now operational with the upgrades. This program successfully completed in 2011, and now all of the US active duty aircraft fly with common/compatible systems.
Exceptions include Block 30/32 F-16s at the Aggressor squadrons in Nevada and Alaska and Block 25 F-16s in training squadrons at Luke AFB, Arizona. Block 25 and Block 30/32 aircraft are concentrated in Air National Guard and Air Force Reserve Command units. A few Reserve Component units do already fly more advanced versions of the F-16.
Block 60 And Beyond
The F-16 Block 60, also known as the Desert Falcon, is the most advanced F-16 produced to date. An internal, forward-looking infrared navigation sensor mounted as a ball turret on the upper left nose is the main feature that distinguishes the Block 60 from previous F-16s. Both single- and two-seat aircraft carry conformal fuel tanks.
The Desert Falcon’s increased-thrust GE-132 engine helps compensate for the increase in weight and payload over the basic F-16. Internal differences, on the other hand, add up to a huge improvement in capability.
The Desert Falcon has many automated modes, including autopilot, auto-throttle, an automatic ground collision avoidance system, and a pilot-actuated recovery system. The recovery system allows pilots to recover the aircraft with the push of a button the moment they sense they have lost situational awareness. The Block 60’s electronic warfare system, produced by Northrop Grumman, is the most sophisticated subsystem on the aircraft. It provides threat warning, threat emitter locating capability, and increased situational awareness to pilots. A fiber-optic databus handles the throughput and speed needed for many of these systems. The maintenance system is laptop-based.
The APG-80 agile beam radar underpins many of the new capabilities of the Block 60. The radar, produced by Northrop Grumman, is an advanced electronically scanned array offering much greater detection ranges. The radar can continuously search for and track multiple targets and simultaneously perform multiple functions such as air-to-air search and track, air-to-ground targeting, and terrain following. The radar vastly improves the pilot’s situational awareness.
Block 60’s General Electric F110-GE-132 turbofan engine produces approximately 32,500 pounds of thrust in maximum afterburner. The engine is a derivative of the F110-GE-129 engine that powers the majority of F-16C fighters worldwide.
The Evolution Continues . . .
In recent years, significant improvements in F-16 capability have been developed and added to the stream of software and systems upgrades that have been a part of the program from its inception. Most recently, the US Air Force is fielding the Automated Ground Collision Avoidance System, or AGCAS, which provides the pilot with improved situational awareness of imminent collision with the ground. The system can take control of the aircraft to avoid a collision if the pilot doesn’t respond to the visual cues.
Additionally, to implement customer requirements for newer, more advanced capabilities and to meet the data processing loads required to fulfill those requirements, the avionics configuration for the F-16V has been developed to keep the F-16 capable and relevant. The V configuration incorporates an improved MMC; upgraded programmable displays generator; an active electronically scanned array radar; a large, high-resolution center pedestal display; and integrated control for the various electronic warfare displays and systems all supported by a gigabit Ethernet architecture.
Still Exceptional
In the 40 years since the YF-16 was flown for the first time in the Air Force Flight Test Center at Edwards AFB, California, it has continued to evolve to meet new requirements for each of the twenty-six customers who operate the F-16 as their front-line fighter. The first production F-16 rolled out of the factory in Fort Worth in August 1978. Since then, more than 4,500 F-16s have rolled off assembly lines in five countries. The F-16 will continue to serve as a front-line fighter and sustainment will extend well beyond 2030.
The present state of the F-16 encompasses a broad range of configurations. While the earliest F-16s perch atop poles for public display, others test the latest weapon and sensor technologies. Those rolling off the factory line represent the most advanced fourth-generation fighter produced today. Even though the F-16 has been flying for forty years, its evolution continues to build on the fundamental strengths of its original design.
Eric Hehs is the editor of Code One.
