Category SA-2 "GUIDELINE" SAM

BOOKS

Anderton, David, Republic F-105 Thunderchief (Osprey Air Combat, 1983)

Bamford, James, Body of Secrets — Anatomy ofthe Ultra-secret National Security Agency (Doubleday, 2001) Broughton, Col Jack, Thud Ridge (J. B. Lippincott Company, 1969)

Broughton, Col Jack, Going Downtown — The War Against Hanoi and Washington (Orion Books, 1988) Campbell, J. and Hill, M., Roll Call — Thud(Schiffer, 1996)

Colvin, John, Twice Around the World (Leo Cooper, 1991)

Davies, Peter E., Osprey Combat Aircraft 84 — F-105 Thunderchief Units ofthe Vietnam War (Osprey, 2010) Davis, Larry and Menard, David, Republic F-105 Thunderchief (Specialty Press, 1998)

Davis, Larry, Wild Weasel — The Sam Suppression Story (Squadron/Signal Publications, 1986)

Eschmann, Karl J., Linebacker — The Untold Story ofthe Air Raids over North Vietnam (Ivy Books, 1989) Fitzgerald, Frances, Fire in the Lake — The Vietnamese and the Americans in Vietnam (Little, Brown and Company, 1972)

Geer, James, The Republic F-105 Thunderchief, Wing and Squadron Histories (Schiffer, 2002)

Hewitt, Maj William A., Planting the Seeds of SEAD (Air University, USAF, 2002)

Hobson, Chris, Vietnam Air Losses (Midland Publishing, 2001)

Jenkins, Dennis R., F-105 Thunderchief, Workhorse ofthe Vietnam War (McGraw-Hill, 2000)

Lashmar, Paul, Spy Flights ofthe Cold War (Sutton, 1996)

McCarthy, Brig-Gen James R., Linebacker II—A View from the Rock (Air War College, 1979)

McNamara, Robert S., In Retrospect — The Tragedy and Lessons of Vietnam (Times Books, 1995)

Michel, Marshall L., The 11 Days of Christmas (Encounter Books, 2002)

Momyer, Gen William W., Airpower in Three Wars (University Press of the Pacific, 1982)

Plunkett, W. Howard, F-105 Thunderchief — A 29-Year Operational History (McFarland and Co., 2001)

78 Pocock, Chris, 50 Years ofthe U-2 (Schiffer, 2005)

Price, Dr. Alfred, War in the Fourth Dimension (Greenhill Books, 2001)

Rasimus, Edward J., When Thunder Rolled — An F-105 Pilot Over North Vietnam (Smithsonian Books, 2003) Rock, Col Edward T. (Ed.), First In, Last Out (The Society of Wild Weasels/Authorhouse, 2005)

Rottman, Gordon L., Osprey Warrior 135 — North Vietnamese Army Soldier 1958—75 (Osprey Warrior, 2009) Thompson, Wayne, To Hanoi and Back — The USAF and North Vietnam 1966—73 (University Press of the Pacific, 2000)

Thorsness, Leo, Surviving Hell — A PoW’s Journey (Encounter Books, 2008)

Tilford, Earl H., Jr., Setup — What the Air Force Did in Vietnam and Why (University Press of the Pacific, 1991) Truong Nhu Tang, A Viet Cong Memoir (Vintage, 1986)

Van Staaveren, Jacob, Gradual Failure — the Air War over North Vietnam 1965—66(Air Force History and Museums Program, 2002)

Wilson, Tom, Lucky’s Bridge (a novel based on the 355th TFW) (Bantam 1993)

Zaloga, Steven J., Osprey New Vanguard 134 — Red SAM: The SA-2 “Guideline” Anti-Aircraft Missile (Osprey New Vanguard, 2007)

Pyotr Grushin, who headed the OKB-2 design bureau that conceived the V-750/ SA-2 in 1953, would have been surprised that “his” missile was used in Vietnam primarily against tactical fighters. Its original purpose was to intercept high-flying American bombers equipped with nuclear weapons, as Premier Joseph Stalin had considered them to be the biggest threat to the USSR. Only at the conclusion of the Vietnam War was it pitted against the B-52 Stratofortress, the opponent that had motivated Grushin’s team 20 years earlier.

Similarly, Alexander Kartveli, a Russian emigrant from Stalin’s hometown, Tbilisi, and primary designer of the F-105 Thunderchief nuclear strike fighter in 1952, could hardly have guessed that his creation would evolve into the USAF’s first dedicated aircraft for the suppression of enemy air defenses (SEAD), particularly the SA-2, over North Vietnam.

Suppressing anti-aircraft fire was an established mission for tactical aircraft, and its dangers were well known. In support of the massive airborne assault codenamed Operation Market Garden in September 1944, four USAAF fighter groups attacked German flak batteries and the 56th FG lost a third of its P-47 Thunderbolts on one mission alone. This role continued through the Korean War and into Vietnam, where anti-aircraft artillery (AAA) was the largest component in the communist North’s air defense network. Dueling with flak gunners was risky, officially discouraged, but sometimes inevitable.

The introduction of surface-to-air missiles (SAMs) in the early 1950s demanded new approaches. Radar-directed missiles were seen as the replacement for air-to-air guns, being the nemesis of both manned fighters and bombers. Tests indicated that their probability-of-kill rate was close to 100 per cent even with unreliable thermionic valve technology that existed at the time. The loss of a Lockheed U-2 spyplane over

the USSR in May 1960 and another over Cuba in October 1962 showed the accuracy of the SA-2 and the difficulties in defeating it. Ten years later, America’s foremost military aircraft were still being destroyed by the same missile over North Vietnam.

In Korea, the USAF was unprepared for the radar-directed AAA which threatened its B-29 bombers, forcing it to resort to World War Il-vintage radar jammers and B-26 Invaders fitted with radar homing. In 1953 the American military responded to the advent of the SA-2 with the funding of urgent electronic warfare research, although fitting SAM warning systems to aircraft like the U-2 still had a low priority.

The Cuban missile threat hastened the development of the Texas Instruments ASM-N-10 (later designated AGM-45 Shrike) as a US Navy anti-radiation missile (ARM) in 1962—64, although it did not appear on USAF aircraft until March 1966. The Bendix Corporation responded quickly to the arrival of SA-2s around Hanoi with a Radar Homing and Warning (RHAW) system proposal for the F-100 Super Sabre that used existing, tested equipment.

By August 1965, after USAF jets began to fall to SA-2s, Brig Gen Kenneth Dempster was tasked with energising the anti-SAM program and finding rapid, operationally practical solutions. His committee recommended a force of hunter-killer aircraft to extend Korean War tactics by using SAM radar detection equipment to identify SA-2 sites rather than merely jamming them.

For Project Wild Weasell, four F-100F Super Sabres carried two systems produced by Applied Technologies — the Vector IV (APR-25) RHAW set with a cathode ray tube strobe showing the direction of a SAM threat, and the IR-133 panoramic receiver which analysed and identified radar emissions. Finally, a WR-300 unit warned of an imminent SAM launch.

As Wild Weasel pioneers, Maj Garry Willard and his four-aircraft F-100F Detachment interrupted their training at Nellis AFB due to the urgent need (as seen by the Pentagon) for “an immediate RHAW capability to counter the missile threat” and headed to Korat Royal Thai Air Force Base (RTAFB). Commencing operations on November 24, 1965, the “det” quickly established many of the tactics used by later F-105F/G crews, including the standard SAM evasion tactic — a “split-S” diving turn into the missile’s trajectory, with a last-second break that the missile could not follow. Capts Allen Lamb and Jack Donovan made the first of nine SAM-site kills on December 22, 1965, attacking and marking the target with guns and LAU-3 rocket pods for F-105D bombers. Lamb recalled, “As I pulled off there was a bright flash. I must have hit the oxidizer supply for the SA-2 rocket motor”.

This engagement introduced a new era of electronic warfare between the crews of the F-100F’s successor, the F-105 Thunderchief, and teams of North Vietnamese conscripts and their Soviet advisors. Operating in hot, dark, claustrophobic radar vans, the missile technicians sat close together on simple metal chairs, grappling with the crude but tricky manual control wheels of “Fan Song” guidance radars and learning to penetrate US jamming and countermeasures. They faced the constant risk of an anti-radiation missile strike on their compartment, or a lacerating cluster-bomb attack. Other troops drove the SA-2’s cumbersome trans-loader vehicles from the SAM sites into crowded urban areas to collect new missiles once the SAM battery’s complement of 12 weapons was exhausted.

In the cockpits of the small numbers of F-105 Wild Weasels, pilots struggled to steer their heavy aircraft through unprecedented levels of AAA, not to mention multiple SA-2 launches, trying in poor visibility to identify camouflaged SAM sites and set up missile attacks on them. Their electronic warfare officers (EWOs, or “bears”) faced an increasing overload of work as they managed the EW systems and weapons panels. They also had to watch for MiGs, despite the very limited view from their cockpits, and monitor crowded communications and navigation channels, while enduring constant high-g maneuvering. Their mission was neatly summarized in the 388th TFW’s Tactics Manual:

The mission of Wild Weasel aircrews generally falls into two roles — Iron Hand to suppress and Wild Weasel to destroy. Tactics employed on the Iron Hand missions are primarily designed to suppress the SA-2 and gun-laying radar defenses of North Vietnam during the ingress, attack and egress of the main strike force. Shrike missiles are used to kill, or at least harass, the SA-2 and/or “Fire Can” (AAA) radar transmitters. Coincidentally the threat represented by the Iron Hand flight also diverts the attention of enemy radar operators from the main strike force and this, in itself, is a form of suppression.

On both sides, courage and ingenuity were at least as important as technology.

F-105F/G THUNDERCHIEF

For the first seven years of the F-105’s development and service, its pilots learned to fly the fighter in single-seat versions – the YF-105A, F-105B and F-105D. By 1963 the increasing complexity, weight and cost of these strike variants meant that it had become too hazardous to allow pilots to train wholly on single-seaters. USAF Air Training Command had requested a two-seat F-105B (designated the F-105C) in 1956, but this was cancelled in favor of the F-105E — a two-seat F-105D variant — the following year. The E-model was also cancelled in 1959 as a cost-cutting measure, but in June 1962 an order for 36 F-105Fs was approved, with another 107 planned for Fiscal Year 1963. The latter were financed by cancelling the last 143 F-105D-31-REs.

F-105Fs were intended to fly the same tactical nuclear strike missions as the F-105Ds. This role dated back to 1952 when Republic’s Chief Engineer, Alexander Kartveli, adapted his RF-84F Thunderstreak design to carry a small tactical nuclear weapon internally. Evolving slowly via YF-105A prototypes into the F-105B, the type eventually entered Tactical Air Command (TAC) service in 1959. Its massive J75 engine could drive it at 750 knots at ground-hugging altitude with a Mk 28 “nuke” aboard, or almost 1,200 knots at 36,000ft. The 45-degree swept wing spanned only 34.9ft (two feet less than a Spitfire from World War II) against a fuselage length of 63.1ft (similar to that of a C-47 Skytrain). With only 385 sq. ft of wing area to support 10 a 47,000lb take-off weight, the F-105B had limited maneuverability, but offered great

stability in its primary strike role. Evading enemy radar via terrain masking, it could outdistance any other fighter at low altitude.

The F-105D proposal in 1957 sought to give all-weather capability, particularly in the European Cold War scenario. A 15-inch fuselage extension allowed a 2,000lb increase in combat weight through the addition of an AN/ASG-19 fire control system,

FC-5 flight control system (FCS) and R-14A radar that was optimized for ground mapping. The jet’s limited all-weather capability came from the FCS, which permitted both visual and “blind” delivery of conventional and nuclear ordnance. The FCS’s terrain guidance mode also enabled the pilot to perform low-altitude navigation in poor visibility. In the cockpit, new vertical tape displays provided basic flight information at a glance. Externally, an arresting hook was added.

In an effort to offset the weight gain associated with these improvements, the aircraft was fitted with a Pratt & Whitney J75-P-19 engine whose water-injection gave it a short-term 2,000lb thrust increase for take-off at increased weight. The M61A1 20mm rotary cannon installed in the F-105B’s nose was moved back to accommodate the larger radar, the weapon drawing ammunition from a drum rather than via belts from a box as with the F-105B.

The first F-105D flew on June 9, 1959, and the 4th Tactical Fighter Wing (TFW), which was selected to introduce the aircraft into frontline service, was in business by late 1962. D-models eventually equipped 12 tactical fighter wings before going on to serve with Air Force Reserve and Air National Guard units until 1984.

In order to preserve the range and combat capability of the F-105D, Republic elected to extend its fuselage by 31 inches for the F-105F through the fitment of a “plug” ahead of the air intake line. The two cockpits were given separate canopies and the electronics compartments were moved behind the rear cockpit. The rear fuselage was strengthened and a new vertical stabilizer some five inches taller and 15 per cent larger in area was also added. These changes, together with beefier landing gear components, added 3,000lbs to the overall weight. Nevertheless, the F-105F could fly the same strike missions as the D-model jet, with the front-seat pilot performing most of the mission-related tasks.

Interest in the F-105F as an anti-SAM electronic countermeasures platform began in August 1965 after several US aircraft had been destroyed by SA-2s. However, the scarcity of F-105Fs meant that the more plentiful, though slower, two-seat F-100F was chosen to flight-test equipment for detecting and suppressing SAM sites. In record time, Applied Technologies, Incorporated (ATI) adapted existing ECM devices and produced the Vector IV RHAW set (based on its System 12 for the U-2), the IR-133 panoramic S-band receiver to locate emissions from the SA-2’s “Fan Song” guidance radar, and the WR-300 receiver that warned of the imminent launch of an SA-2.

Combat-tested in four F-100Fs, this equipment set, codenamed Wild Weasel I, enabled a flight of F-105Ds led by a Weasel Super Sabre to destroy a SAM site only five months after the first SA-2 shoot-down of a USAF fighter. However, the IR-133 was susceptible to jamming by USAF EB-66 aircraft operating in the same area and unable to home onto a “Fan Song” while the F-100F was maneuvering energetically. The

equipment did not indicate whether the aircraft was being tracked by a SAM either. 11

As part of their dominant role in the air war over North Vietnam, F-105D and F-105F Thunderchiefs attacked SA-2 sites as soon as permission was granted to do so. In this typical 1970 scene at Takhli RTAFB, Lt Col Jack Spillers, commanding the 355th TFW’s 357th TFS, begins a take-off roll in the relatively spacious single cockpit of F-105D 62-4229, named after his wife. Note that the Mk 83 1,000lb high explosive bombs attached to the jet’s center pylon have been fitted with fuze extenders. (Mrs J.

Spillers via Norman Taylor)

Republic Aviation had already tested an AN/APS-107 RHAW in an F-105D but rejected it in September 1965 in favor of the Vector IV as an urgent means of reducing the escalating attrition amongst Thunderchief units over North Vietnam. ATI and the Sacramento Air Material Area (SMAMA) successfully completed an installation in F-105D 62-4291 within five days, and a second aircraft was ready on 27 October 1965. This F-105D (61-0138) was fitted with a Bendix DPN-61 homing receiver, a fin-cap radar-warning receiver (RWR) and a SAM threat warning CRT display as the

F-105G-1-RE 63-8336 PATIENCE of the 17th WWS/ 388th TFW in February 1973. This aircraft entered service as an F-105F with the 23 rd TFW in September 1964, and in March 1968 the jet went to war as a single-seat Combat Martin jammer aircraft with the 388th TFW at Korat RTAFB, although it actually flew most of its missions in a strike or Iron Hand role. Transferred to the 355th TFW in May 1969, 63-8336 then served with the 18th TFW at Kadena AB, prior to being flown back to the USA and placed in storage under 23 rd TFW management at McConnell AFB. Converted to F-105G configuration in 1972, the aircraft returned to the war torn skies of North Vietnam with the 17th WWS for Operation Linebacker I. The Thunderchief continued to fly Wild Weasel missions from Korat RTAFB until October 1974, when it was transferred to the 35th TFW and thence to ANG units and final storage at Davis-Monthan AFB in April 1982, with more than 4,000 flying hours on

first attempt to equip the jet for the SEAD role under project Wild Weasel II. This included F-105F 62-4421 using the AN/APS-107, the US Navy’s AN/ALQ-51 and external QRC-160-1 jamming pods.

The project was quickly replaced by Wild Weasel III, which focused solely on the F-105F with the AN/APR-25 (Vector IV), AN/APR-26 (WR-300, conceived by ATI’s Bill Doyle) and IR-133 — basically the Wild Weasel I suite. It was initiated on January 8, 1966 by Brig Gen Kenneth C. Dempster, who headed the USAF Anti-SAM Task Force from August 13, 1965. His brief from the outset had been to develop effective systems for tactical aircraft that allowed them to protect themselves from radar-directed weapons. A primary objective was the evolution and speedy deployment of fast hunter- killer teams to locate SA-2 sites using WildWeasel detection aircraft and destroy them with Iron HandF-105Ds equipped with 2.75-inch rockets, bombs and 20mm cannon. Republic and SMAMA had quickly modified the prototype F-105F (62-4416) to serve as the Wild Weasel III test-bed by February 3, 1966, and work began on six more F-105Fs while the prototype started a hasty test program at Eglin AFB.

The speed of the latter caused numerous quality control and technical problems with the installations, particularly the AN/APR-25, which failed to equal its performance in the F-100F because of inadequate co-axial cabling. With an imminent deployment to Korat RTAFB looming for five of the Thunderchiefs, all seven aircraft were re-worked and re-tested repeatedly, while six more F-105Fs were re-fitted in May 1966. An additional system was installed to help pilots locate SAM sites, particularly when they were well camouflaged. This ATL AE-100 system used a pattern of small antennas around the F-105F’s nose to receive azimuth and elevation information on an emitting “Fan Song” and display it so that a pilot could establish the direction of the threat radar. Delays in installing this gear, and in testing the rival AEL Pointer III system and the QRC-317 SEE-SAMS threat detection and evaluation system, meant that the five WildWeasel III-1 aircraft could not fly to Korat until May 28, 1966.

Although SEE-SAMS was initially rejected, development continued by North American Aviation and an improved SEE-SAMS B variant was evaluated in the Korat aircraft. In a period of experimentation with evolving ECM technology and tactics, together with the frequent development of relevant new products by the US defense industry, the WildWeasel F-105s received constant modification so that each aircraft soon had minor differences from the rest.

At Korat and Takhli RTAFBs the Weasels expanded the tactics pioneered by Wild Weasel IF-100F crews, although they initially continued to use the F-105F as a pathfinder/flight leader for three F-105D bombers on Iron Hand hunter-killer operations. With the adoption of the US Navy’s AGM-45 Shrike ARM from March 1966, however, the F-105F could now also make stand-off attacks on “Fan Song” radars rather than merely marking them with 2.75-inch rockets for F-105D bombers.

The employment of the Shrike also changed the role of Weasel crews during 1966-67, for missile-equipped F-105s could now suppress SAM batteries simply through their mere presence, forcing a “Fan Song” team to shut down rather than attract a radar-homing missile. It was no longer necessary to risk life and limb 14 physically knocking out an SA-2 site with bombs and/or rocket projectiles.

Another batch of 18 F-105Fs was pulled out of the training program from July 1966, these jets being fitted with ER-142 receivers operating in the E-G frequency bands in place of the IR-133 — the new receiver displayed its information on two panoramic cockpit scopes. The ER-142 was in turn superseded by the ER-168 (AN/APR-35), installed with the AN/ALT-34 jamming system. An improved SEE – SAMS set (eventually re-designated AN/ALR-31) boasting additional wing-tip antennas was installed in a number of F-105Fs in 1968.

Various built-in jamming systems, including the US Navy’s AN/ALQ-51 deception jammer, were tested to provide anti-SAM protection. All F-105s operating over North Vietnam were required to carry jamming protection, but pylon-mounted QRC-160- 1/8 pods used up a weapons station and could interfere with the Wild Weasel equipment. The solution to this problem came in the form of “split” AN/ALQ-101 pods, attached to either side of the lower central fuselage, housing QRC-288 (later QRC-335) jammer components. As the AN/ALQ-105, this system equipped the ultimate Thunderchief Wild Weasel, the F-105G.

The jet’s most important enhancement was the provision of AGM-78A Mod 0 Standard ARM capability. This weapon — another US Navy initiative — had a warhead three times larger than the Shrike’s and a range three times greater than its 12-mile radius. The latter meant that aircraft could now fire an ARM from outside the effective range of an SA-2. And while the Shrike had to be launched almost directly at its target, the Standard ARM could be made to turn up to 180 degrees before homing on a

hostile radar. If that radar was turned off (which would cause a Shrike to break lock and fail), the AGM-78 used a memory circuit to log the last known position of the radar signal and continue to head towards it.

Fourteen F-105Fs were modified to carry the AGM-78 from September 1967, and eight of these entered combat fromTakhli in early March 1968. A year later the ECM suite was radically updated to handle the AGM-78A Mod 1 missile and, in due course, the AGM-78B. Retaining only the AN/ALT-34 jammer and AN/ALR-31 (SEE – SAMS), the new installation used an AN/APR-35 panoramic receiver and AN/APR-36/37 sensors in place of the AN/APR-25/26. New missile control panels, a tape recorder and a tracker to feed back information on the missile’s flight in order to estimate its likely success rate were also installed. Deliveries of revised “Mod 1” aircraft began in January 1969, and the jets’ success in combat persuaded the USAF to standardize all surviving F-105F Weasels as Mod 1 airframes, re-designating them F-105Gs. With the addition of 12 new conversions, this placed 61 F-105Gs in the active inventory. They all received the AN/ALQ-105 suite in due course too, although a few F-105Gs entered combat before these external fuselage pods were added.

In this guise the F-105 Wild Weasel fought through the final stages of the Vietnam War in 1971-73, out-performing its intended replacement, the F-4C Phantom II Wild Weasel TV. The latter lacked AGM-78 capability, and from 1966 onwards never reached the standard of electronics systems reliability achieved by the F-105G.

In March 1946 Gen Carl Spaatz, commanding the US Army Air Forces, asserted that “Strategic Air Command will be prepared to conduct long-range offensive operations in any part of the world”. The success of heavy bombers during World War II had demonstrated their devastating power. Post-war, Strategic Air Command (SAC) acquired 2,042 jet-powered B-47 Stratojets and then 744 B-52 Stratofortresses capable of delivering nuclear weapons at 550kts over a 3,000-mile combat radius.

Faced with the formidable task of defending its vast land area against both this threat and high-flying US spyplanes, the Soviet Union urgently promoted a new generation of interceptor fighters, but for the defense of its cities another layer of protection was required that would be more effective than fighters or guns. In 1945 Soviet scientists used captured data from German surface-to-air guided missile projects to design first-generation SAMs, but internal political competition prevented their completion. By 1951 Joseph Stalin had instigated a new project, codenamed Berkut, which surrounded Moscow with SAM batteries and radars connected by ring-roads. The first batteries were declared operational in 1956, using the V-300 (NATO codename SA-1 “Guild”) missile conceived by fighter designer Semyon Lavochkin.

A second, mobile system was needed for the protection of wider areas of the Soviet Union, and in November 1953 the Almaz design bureau’s Boris Bunkin headed a team that conceived the S-75, with Lavochkin-trained Pyotr Grushin as principal designer.

F-105 WILD WEASEL

As the USAF’s first major SEAD aircraft, the F-105F/G enabled its crews to establish operational techniques for counteracting SAMs that were vital during the Vietnam conflict and still remain valid today.

Designed as a strike fighter to fly very fast, low and straight, the F-105 had the speed to duel with SAMs, although it lacked the agility in this role enjoyed by its successors like the F-4G and F-16D Block 50. It was 100mph faster than the F-100F Wild Weasel I (which tested the initial Wild Weasel electronics package operationally), however, thus allowing the F-105F/G to approach targets at low altitude at the same 500+ knots speed as the F-105Ds or F-4 Phantom IIs that accompanied it as bombers. The Thunderchief’s small wing and powerful Pratt & Whitney J75-P-19W engine enabled the aircraft to out-run all Vietnamese Peoples’ Air Force (VPAF) fighters – with the possible exception of the MiG-21MF – at low altitude.

The J75 powerplant was a development of Pratt & Whitney’s very reliable JT-3/J57 turbojet, designed in 1949 and crucial to the success of the first three “Century Series” fighters, the North American F-100, McDonnell F-101 and Convair F-102, as well as Boeing’s B-52, 707 and KC-135, among others. The engine also powered the two YF-105A prototypes. More than 21,000 J57s had been built by 1959 when Pratt & Whitney enlarged it by replacing the first three low-pressure turbine stages with two 24 more powerful fan stages. The new engine was designated the J75. Power with

afterburning increased from 16,000lbs thrust to 26,500lbs with water injection, and fuel economy was also improved, although it still burned JP-4 at almost 1,000lbs per minute at full thrust! The engine was fed by innovative forward-swept, variable-area intakes with moveable “plugs” and bleed-air doors to regulate the air volume at different airspeeds to avoid stalls.

In early service with F-105 units the 20ft long engine sustained a series of fires. This problem was solved by providing the jet with additional cooling ducts in the rear fuselage. Although the J75 usually proved to be tough and reliable, in combat, engine

Like many other 1950s fighters, the F-105 had a removable rear fuselage for access to the engine. This had the added advantage that damage to a rear fuselage could be repaired while the aircraft flew missions with a rear section borrowed from another F-105. In this photograph 388th TFW maintainers manhandle a massive J75 engine on an awkward-to-maneuver Model 400A hydraulic support trailer. (Fairchild-Hiller/Republic Aviation)

failures continued to be the second most common cause of F-105 losses next to battle damage. This was partly because the engines were often run at their maximum thrust for long periods, but losses declined after engine modifications in 1968.

The F-105 introduced numerous groundbreaking technological innovations, and like the J75, some of these took several years to get right. Probably the most troublesome element of the aircraft’s avionics was its complex General Electric ASG-19 Thunderstick fire control system. Indeed, its low serviceability rate earned the F-105 a poor reputation amongst USAF maintainers. Thunderstick offered radar search and ranging functions for visual and “blind” bombing, as well as an air-to-air interception mode.

Modification programs for the aircraft, including 29 major updates in 1967 alone, increased survivability. One of these, the pilot recovery system, was a response to the many combat losses caused by the F-105’s highly vulnerable hydraulic system. Designed for missions where small-arms fire was not anticipated, the system had hydraulic lines located along the aircraft’s belly. Combat had quickly revealed that even modest battle damage to a line usually resulted in a rapid loss of control as the fluid drained away and the stabilator moved to an unrecoverable pitch-down position.

From 1967, a cockpit switch activated a lock to secure the stabilator in the neutral position, allowing the pilot a little more time to fly to a safer area using his throttle and flaps to provide limited control. A further system introduced an emergency hydraulic reservoir pressurized by a ram-air turbine to give pilots a chance of safe recovery to base. Lines for this system ran in a new fairing above the rear fuselage.

The aircraft’s normal General Electric FC-5 automatic flight control system gave the option of stability augmentation in manual control or fully automatic mode for toss-bomb delivery and landing approaches.

WILD WEASEL ARMAMENT AND ELECTRONICS

Two-seat Thunderchiefs retained the M61A1 20mm rotary cannon and five weapons stations of the F-105D. The centerline and inboard pylons were plumbed for fuel, with a 450-gallon or 650-gallon centerline tank and a 450-gallon tank on each inboard pylon. Internal fuel amounted to 1,135 gallons, with a further 390-gallon tank occupying the internal bomb-bay. Typical F-105F/G weapons options included six 500lb Mk 82 low-drag general purpose bombs or five CBU-24/B canisters replacing the centerline tank, one or two AGM-78 Standard ARMs (F-105G only) replacing fuel tanks on the inboard wing pylons and either AGM-45 Shrikes or single cluster bomb units on the outer pylons. If AGM-78s were loaded, they also required special General Dynamics LAU-80 pylons. Each missile, with its pylon, weighed 1,600lbs.

A shortage of ordnance pylon space was a problem for the Weasel mission, particularly when crews were ordered to carry the QRC-160-1 jamming pod on all missions over North Vietnam in early 1967. The pod not only used up a pylon, it also interfered with the Wild Weasel ECM equipment.

The two cockpits, each fitted with a Republic-designed rocket-powered ejection seat, were essentially similar to the F-105D version, with full flight instrumentation and some armament controls repeated in the rear pilot’s “office”. F-105Fs sometimes operated as single-seat bombers to make up F-105D numbers, and ten were modified as single-seat Combat Martin aircraft with an AN/ALQ-59 communications jamming system replacing the rear seat. Their purpose was to jam VPAF MiGs’ ground control intercept (GCI) signals, although they seldom if ever performed this role in combat. All of these aircraft were later re-fitted as F-105Gs.

Changes to the Wild Weasel ECM packages in the F-105F and early F-105G airframes throughout 1966—68 resulted in the rear cockpits being frequently modified. The standard F-model engine and flying control panels were increasingly replaced by

The General Electric T171 cannon fitted in the nose of the F-105 revived a late 19th century design which added an electric motor to a “Gatling” rotary, multi-barrel gun. It entered production as the M61A1 in 1957, and its compactness, light weight and firing rate of up to 6,000 rounds per minute made it ideal for the F-104 Starfighter, F-105 Thunderchief and later fighters. In the F-105D, F and G, its 1,028 rounds of linkless 20 mm ammunition (allowing about ten seconds of firing) were stored in a drum that also collected empty shell cases. The hydraulically-powered gun weighed 275lbs – little more than half the weight of a full ammunition load.

F-105 MISSILES

Up to four Texas Instruments AGM-45 Shrikes could be carried by the F-105, although the usual load was two.

The ten-foot long, 390lb AGM-45A/B – the world’s first dedicated anti-radiation missile – was produced in 21 sub-variants, distinguished mainly by minor changes in their guidance sections and seeker heads. Its 147lb warhead and 18-mile effective range were limiting factors. Nevertheless, more than 18,500 were produced between 1963 and 1982. The appreciably larger General Dynamics AGM-78 Standard ARM was manufactured for the US Navy and USAF from 1967 through to 1978, the 15ft-long weapon boasting a 215lb warhead. A shortage of AGM-78s and the F-105’s high fuel consumption when carrying the bulky weapon resulted in typical ordnance loads of a single Standard and two Shrikes per jet, with a 450-gallon fuel tank “balancing” the AGM-78 on the opposite wing pylon. Although more effective than the Shrike, the Standard’s overall success rate was still only around the 20 per cent mark.

Between April 1 and September 30, 1972, F-105Gs launched 230 AGM-78s, although there was a failure rate of more than 25 per cent in the first two months that led to a temporary “grounding” of the missile. Rocket motors were also sometimes cracked in transit, causing premature detonation – motors were x-rayed on delivery thereafter. The smaller AGM-45 proved to be quite difficult to discard in an emergency, as it lacked an explosive jettison system for either the missile or its pylon. (USAF)

displays and controls for the AN/APR-35, AN/APR-36 and AN/ALR-31, while the introduction of the AGM-78 missile required the installation of another control panel and 14-channel tape recorder. Key components were the IR-133 display that provided indications of “Fan Song” activity.

The AN/APR-25/26 sensors “read” the SA-2’s signals, enabling the pilot to home onto “Fan Song” emissions. The system’s cockpit display included a yellow “launch” light to show that an SA-2 was headed towards the F-105. Within the correct range and with the aircraft pointed at the threat emitter, an AGM-45 Shrike could pick up

The standard bomb-load for F-105D/Fs throughout much of the war was six or eight 750lb M117 bombs, although CBU or “slick” Mk 82 bombs were often more effective against SAM sites. This 469th TFS/ 388th TFW flight is bombing “straight and level” above clouds early in 1967 – one of the most likely ways to attract a SAM that allowed insufficient time for the F-105s to avoid it. 62-4325 crashed near Korat when the flight control system failed during a test flight on March 14, 1967. (Lt Col Jack Spillers via Norman Taylor)

stable flight on launch. This burned for four to five seconds and then fell away, leaving the Isayev S2.711 sustainer motor to maintain flight at Mach 3. The latter burned hypergolic liquid propellant comprising TG-02 (50 per cent isomeric xylidine, 48.5 per cent triethylamine and 1.5 per cent diethylamine), with AK-20 fuming nitric acid as the oxidizer. This specification was derived from the Wasserfall.

A turbo-pump was required to supply the motor with OT-155 Isonite (isopropyl nitrate) liquid fuel sufficient for a 22-second engine burn. The later Item 20D Volkhov development of the S-75 used a different fuel comprising 56 per cent kerosene and 40 per cent Trikresol, with a TG-02 “starter fuel” supply to ignite the mixture. This was much safer to handle and store than the volatile mix used in the Dvina or Desna (“Guideline Mod 1”) models. For the North Vietnamese, a shortage of technicians qualified to perform these tasks meant that fewer than 40 missiles could be assembled and filled with fuel, oxidizer and compressed air daily.