Fighter Wing: A Guided Tour of an Air Force Combat Wing

by Tom Clancy

  All the basic GBU-15s can be launched from a maximum range of 8 miles/14.6 km. at low altitude, and up to 20 miles/36.6 km. at higher altitudes. The key to this relatively long range is the lift capabilities of the cruciform wings at the front and rear of the GBU-15; these make the bomb an unpowered glider, with much greater maneuverability than previous HOBOS.

  Following Desert Storm, several new variants, called the GBU-151 series, came into service with the Air Force. But at an FY-1991 cost of $227,000 per copy, a GBU-15 is anything but cheap, and further development is unlikely. There is, however, one GBU-151 variant which is rapidly gaining momentum, the Air-to-Ground Missile (AGM) -130. The AGM-130 is basically a GBU-151 with a small rocket motor strapped to its belly. This has the effect of extending the AGM-130’s range to 16 nm./30 km. at low altitudes, and up to 40 nm./45.7 km. at higher release altitudes. It’s an impressive set of capabilities for one family of weapons, though it places a great burden of responsibility on its operators. WSOs assigned to operate the GBU-15/AGM-130-series weapons have to be carefully trained, and have a delicate touch, to get the most out of this most accurate of PGMs.

  Laser-Guided Bombs: The Paveway Series

  Once there were two bridges that were the stuff of nightmares to U.S. pilots who flew over North Vietnam. The Paul Doumer Bridge over the Red River in Hanoi and the Dragon’s Jaw Bridge (Ham Rung in Vietnamese) near Thanh Hoa were the toughest targets in a war full of tough targets. Prior to 1972, despite the efforts of thousands of U.S. Air Force, Navy, and Marine strike sorties, millions of pounds of bombs, and dozens of lost airplanes and killed and/or imprisoned aircrews, the Paul Doumer was only dropped for a few weeks at a time. Then it would quickly be repaired, to carry rail traffic south, laden with supplies for the ground war in South Vietnam. Even worse, despite every effort that the Department of Defense could devise in the 1960s, the Thanh Hoa bridge was never dropped.

  Then, in just four days of May 1972, both targets went down for good, the most visible sign of a new weapons technology which saw its first use in 1967—the laser-guided bomb (LGB). On May 10th, 1972, sixteen F-4Ds from the 8th Tactical Fighter Wing (TFW) at the RTAFB at Ubon, Thailand, roared down on the Paul Doumer Bridge. Twelve of them were each armed with a pair of the new 2,000 lb./909.1 kg. LGBs. When the smoke and spray from the exploding bombs subsided, the bridge was heavily damaged and closed to all traffic. Amazingly, not one of the strike aircraft was damaged.

  Then, the next day, four more 8th TFW F-4Ds again attacked the Doumer Bridge with LGBs, this time dropping several spans. After several more applications of LGBs, the bridge would not be rebuilt until after the cease-fire in 1973. As an added bonus, the control bunker for the entire North Vietnamese air defense system at Gia Lam airfield was destroyed by four more LGB-ARMED F-4Ds from Ubon.

  The crowning achievement came two days later when the laser bombers of the 8th TFW went after the big one: the Dragon’s Jaw. It took everything the ordnance shop and contractor techreps at Ubon could put together, including some specially built 3,000 lb./1,363 kg. LGBs; but when the smoke and limestone dust cleared, one whole end of the bridge had been lifted off of its abutment and heaved into the river.

  The weapons that did this amazing job were certainly not the most advanced or sophisticated ever deployed by the U.S. to Southeast Asia. On the contrary, first-generation LGBs were extremely simple in concept and execution, yet they have been the most successful type of PGM in history. Like the ubiquitous AIM-9 Sidewinder, a simple concept behind the LGB paid massive dividends when it got to war.

  If you are over forty, you probably remember when the magic of the laser beam was first touted by its inventors at Bell Labs. Laser stands for Light Amplification by Stimulated Emission of Radiation. What it means is that a coherent (composed of only one primary wavelength) beam of light with a very high amplitude (bright in the extreme) can be produced and manipulated. The first lasers relied upon solid materials like synthetic ruby to provide a medium to produce the laser light. Today, most lasers are based on gases like carbon dioxide (CO2) or argon (AR). At the time of their introduction, lasers promised to become the “death beams” envisioned by science fiction authors like Jules Verne and H. G. Wells. But the truth was somewhat more modest, for the lasers of the 1960s had nothing like the power required to burn through the solid metal of a rocket or aircraft at tactical engagement ranges.

  Then in 1965, a simple idea for using the laser in a weapons system came to a small engineering team at Texas Instruments (TI). Weldon Word, the brilliant engineer who led the team, decided that instead of using the laser as a weapon, he would use the laser as a way to guide a weapon. Laser light, because it is coherent and tends to stay in a tight beam, has the ability to mark a very small target from a long distance. This means that a seeker could be devised that would “see” only a specific (coherent) frequency of laser light and guide onto it, much as the AIM-9M seeker looks for specific “colors” of light to home in on. It’s like shining a flashlight in a completely dark room. If you are human, all you can see is the target illuminated by the flashlight.

  Simple as this sounds, it posed daunting technical and financial problems for Weldon Word and his TI team. As a starter, there was not much money to develop this new strike technology. In the mid-1960s, DoD was offering $100,000 for ideas that could be put to winning use in Vietnam. But only $100,000 until the ideas had been tested and proven. For Word and his team, this meant the entire system—the seeker/guidance package, the laser “flashlight” (designator), and the warhead—had to be made for that $100,000, and not one penny more. Even in 1965, this would buy only a few thousand man-hours of TI engineering and technical talent, and a small amount of technical hardware for testing the concept. With only a short time available for development, the team made some important decisions. One of the first was that the warhead sections of the new guided bombs, now called Paveway, would be composed of normal 80-series LDGP bombs. The seeker and guidance sections would literally be “screwed” onto the LDGP bombs, providing a solid airframe for the whole package. This meant that the warheads, fuses, and assorted other equipment could be supplied, at no cost to TI, as government-furnished equipment (GFE). Then, rather than building the laser designator from scratch, they adapted a design from a scientist in Alabama. Finally, the team obtained their parts for the laser seeker from a West German salvage firm. Wind-tunnel testing of the proposed bomb package was found to be too expensive, so Weldon Word had his team test the bomb shapes with subscale models in a swimming pool.

  In spite of the “low ball” approach to the problem, the result was successful beyond the wildest dreams of anyone at TI or in the Air Force, even though the first Paveway laser designator (called Paveway I) was about the size of an old sheet-film camera, was bolted to the canopy rails of an F-4 Phantom, and was manually aimed through a telescopic lens by the backseater. Once this was done, then another aircraft had to fly over the target and drop the bomb. As might be imagined, this made the designating aircraft highly vulnerable to AAA guns and SAMs. Nevertheless, the results of the Vietnam combat tests held in 1967 were good enough for the Air Force to order the Paveway guidance kits into limited production. Eventually, the “limited” production wound up totaling over 25,000 units (each virtually hand-built) that were dropped during the Vietnam War. And amazingly, some seventeen thousand hits were scored, for an overall combat success record of some 68%.

  But maybe even more amazing was the way Paveway bombs redefined the word hit. With LGBs frequently generating average circular error probability (CEP) miss distances under 10 feet/3.05 meters (a typical Vietnam-era F-4D CEP with “dumb” LDGP bombs was commonly 150 feet/45.7 meters), it frequently only took a single bomb from one plane to destroy a target which previously took a whole squadron of fighter bombers to hit. Quickly, the cry of “one bomb, one target” became a hallmark of LGB performance around Southeast Asia. As if to highlight the economy of the LGB effort further, a Paveway I guidance kit cost only about $
2,700 in 1972 dollars—cheap compared to over $20,000 for a GBU-8 E/O guidance kit.

  Paveway caused a revolution in aerial warfare, and it showed during the final U.S. air campaigns of the war, Linebacker I/II. During these efforts, which ran from May 1972 until January 1973, Paveway LGBs were the “magic bullets” of the American arsenal. They were everywhere, doing everything. In the south, LGBs from the 8th TFW (the only unit equipped with them at the time) helped stop the armored drive of the North Vietnamese at An Loc with an early demonstration of what would become known as “tank plinking” during the 1991 Persian Gulf War. In the north, they were dropping every vital bridge between the Chinese border and Vinh, as well as a variety of other vital targets.

  Now, with all this success, there also came problems. While the LGB seeker would guide the bomb to an almost perfect bull’s-eye every time, the bomb had to be dropped within a fairly narrow “basket” in the sky (within a few thousand feet of a “perfect” ballistic launch point) for the bomb to have the necessary energy or “smash” to reach the target. This meant that in Vietnam, the Paveway I-series bombs had to be dropped from medium to high altitude (above 10,000 feet/3,048 meters); low-level drops (less than 10,000 feet/3,048 meters) were completely out of the question. In addition, clear visibility in daylight was a must, because the early Paveway I designators did not have low-light or thermal imaging systems. In fact, until the introduction of the AAQ-26 Pave Tack targeting and designation pod in the late 1970s, the designators were the major limitation in the use of LGBs.

  The first designation system that made LGB drops in high-threat areas viable was the Pave Knife built by Ford Aeronutronic (now Loral Aeronutronic). Hand-built and fielded by a team led by the legendary optical engineer Reno Perotti, the six prototype Pave Knife pods that were available became one of the single most important factors to the continued success of the Linebacker campaigns in 1972.

  In the late 1970s, DoD began fielding a new version of the bomb-guidance kit, the Paveway II. Essentially a production version of the hand-built Paveway I-series kits, they provided the USAF, USN, and USMC with their primary PGM capability well into the 1980s. They have even enjoyed a measure of export success, including use by the British in Desert Storm. In fact, Paveway II-series kits are still in the U.S. and NATO inventory, and will continue to soldier on well into the 21st century.

  The Paveway II kits come in three varieties, broken down by the following bomb configurations:

  The Paveway II-series bombs proved to be extremely successful, and have enjoyed a long and useful career. The first attempted combat use of Paveway II appears to have occurred in October 1983, when an A-6E from the USS John F. Kennedy (CV-67) dropped several LGBs on targets in the Beirut area. Unfortunately, problems with the ground-based laser designator caused them to miss their assigned targets. They saw their first really successful combat trials during Operation Prairie Fire in 1986, a series of confrontations between the U.S. Navy and Libya in the Gulf of Sidra. During the famous “Line of Death” confrontations, USN A-6Es used Paveway II-series bombs to help destroy/disable several Libyan patrol boats. Later, they were used during Operation Eldorado Canyon, the joint April 1986 USAF/USN/ USMC raid on Benghazi and Tripoli.

  One of the Paveway II configurations, the diminutive 500 lb./227.3 kg. GBU-12, proved to be one of the most important weapons of the 1991 Persian Gulf War. In late January and early February of 1991, CENTAF BDA teams showed that the “battlefield preparation” in the KTO (Kuwaiti Theater of Operations) was not destroying enough armored vehicles and artillery pieces with standard LDGP bombs to meet the proposed attrition target of 50% prior to the start of the ground war.

  To help overcome this problem, Major General Buster Glosson, the CENTAF Director of Operations, came up with an idea called “tank plinking.” General Charles A. Horner, the commander of CENTAF during the war, is said to have been told by the commander of CENTCOM, General H. Norman Schwarzkopf, to never call this tactic “tank plinking.” General Horner, always the obedient fighter pilot, promptly ordered his staff to make sure that everyone always called it “tank plinking.”

  Here is how tank plinking worked. A flight of F-111Fs or F-15Es would fly over an Iraqi artillery or armored unit shortly after sunset. Since the sand of the desert cooled faster than the military equipment dug in among the dunes, the vehicles and artillery tended to show up as “hot spots” in the aircraft’s FLIR targeting systems. They would then drop one of the “old” GBU- 12s on the desired target, and the results were, in a word, spectacular. Despite what you might think, even a main battle tank cannot have armor everywhere, especially on top. Thus, when one of the “little” LGBs hit one, the target would go up in flames, and the BDA assessments were quite positive. The fact that an F-111F might carry four GBU-12s, and an F-15E up to eight, meant that tank plinking was a surprisingly economical way of killing targets up in the KTO. Every night, for several weeks in early February 1991, the 4th and 48th TFWs would send pairs of F-15Es and four ship flights of F-111Fs into the KTO to hunt artillery and armor targets. The results were spectacular. Often, the small formations would come home with anything from twelve and sixteen targets killed per mission.

  Combined with the capabilities of an integrated thermal imaging/laser designation/weapons delivery system, the Paveway II-series LGB was a formidable weapon when properly employed. Formidable, but very limited. Paveway II still had a very small launch “basket,” which diminished its utility in high-threat environments. In particular, its low-level capabilities were highly restrictive, making its utility in that mode marginal. Even with drops from 20,000 feet/6,096 meters, the favored altitude for Paveway II drops, there were challenges for the crews.

  Even before Paveway II went into combat, the Air Force and TI had begun to develop the replacement for the Paveway II under a program called the Low-Level Laser-Guided Bomb (LLLGB). Begun in 1981, it was designed to overcome the shortcomings inherent in the previous Paveway II bombs and take full advantage of the new series of laser designator systems being deployed worldwide. The result was the Paveway III series of bombs, which came into service in the mid-1980s.

  The key was to be an all-new guidance section, which would be equipped with a microprocessor-controlled digital autopilot adaptive to the flight and release conditions. There are a variety of settings for delivery aircraft, flight mode, warhead configuration, laser coding, and delivery profile. Even more important, with a change of the Programmable Read Only Memory (PROM) chips which hold the autopilot software, the basic guidance package can be adapted to a variety of bomb configurations and capabilities. The changes to Paveway III start at the front of the seeker with the seeker dome, which is made of Lexan plastic with a fine wire mesh. Inside this dome is an optics housing containing a four-quadrant laser sensor and optics to focus the spot of laser light from the laser designator. The simple four-quadrant detector in the seeker is the touchstone of the Paveway program’s simplicity, and is one of the keys of its success. And the sensitivity of the seeker itself has also been improved, so that even low-power laser designators (or standard designators degraded by weather) can be used. The seeker housing is gimbaled in two axes, and can scan in a bar (horizontally, back and forth), box (rectangular), or conical (circular) mode. Aft of the seeker is the guidance electronics section, which contains the autopilot, laser decoding, and signal processing circuitry, as well as the rotary switches for programming the bomb. The control setting switches are mounted flush with the exterior of the airframe, and can be set with almost any flathead tool, though the “ordies” (ordnance technicians) from the 391st Fighter Squadron at Mountain Home AFB (they fly the F-15E Strike Eagle) tell me that a quarter works best for this job.

  The laser seeker, guidance electronics, and control section form what is termed the Guidance and Control Unit (GCU), which is attached to the front of the selected warhead. Paveway LGBs have always made use of standard USAF munitions as the warhead; and Paveway III is no exception. It can be attached to any o
f the 80-series bombs, as well as the BLU-109/B penetrating warhead. At the rear of the warhead is mounted the cruciform airfoil group. This is a tail section equipped with four pop-out wings to help stabilize the weapon during its flight. Along with mounting lugs for the bomb rack on top of the weapon, this is the makeup of a complete Paveway III LGB.

  The first production versions of the Paveway III were the GBU-24 family, which entered service in the mid-1980s. Designed as the general purpose LGB, the GBU-24 quickly became the primary weapon of the F-111Fs of the 48th TFW at RAF Lakenheath. It is the airfoil group, with its large spring-deployed planar wings, that makes all the difference in expanding the launch and delivery envelope of the GBU-24. When the wings are fully extended some two seconds after the bomb is dropped, they have twice the lift area of the Paveway II-series airfoil group, and give the GBU-24 a glide ratio of 5:1, meaning that for every foot/meter of altitude lost in flight, the bomb can travel forward five feet/meters. This means that the launch envelope for the GBU-24 is vastly greater than the Paveway II-series bombs, and gives it the energy and maneuverability for a lot of tricks.

  The second version of the GBU-24 family, while a bit different, became one of the stars of Desert Storm. This variant has a BLU-109/B penetrating bomb warhead, designed to punch through heavy reinforced concrete and armor. Called a GBU-24/B, it was Saddam Hussein’s greatest nightmare, and his worst tactical surprise when Desert Storm kicked off. With the exception of a handful of command bunkers outside of Baghdad, it was capable of destroying every hardened target in Iraq. This included the Yugoslav-built hardened aircraft shelters (HASs) that had been previously thought to be impervious, even to a near-miss by a tactical nuclear device! The GBU-24/B is composed of the same components as the basic GBU-24/B, with the difference of the BLU-109 being substituted for the Mk 84. In addition, there is a spacer attached to the bomb body called an ADG-769/B Hardback. This helps maintain the same tail clearances as the larger-diameter Mk 84. In addition, there is only one fuze, an FMU-143/B delayed action unit mounted in the rear of the BLU-109/B. Other than that, the two models are identical, with the necessary software to operate both models already being built into the common guidance and control unit. A third variant, the GBU-24B/B, is an improved GBU-24A/B.