FB-111A Formation, December 1983
FB-111A Formation, December 1983
'Dark Vark' FB-111A 'Aardvark'
Nuclear Gravity (Free Fall) Bombs
SRAM (Short Range Attack Missile)
In the 1960s the B-58 Hustler, Strategic Air Command's futuristic-looking medium bomber, had a single mission profile: fast, high altitude penetration of enemy airspace. SAC doubled down on that mission profile with the B-70 Valkyrie bomber project - canceled in 1961 and relegated to a flight test program. Fast and low were the new watch words after the shoot down of Gary Power's U-2 in 1960. It was also clear that there would be further advances in surface to air missile technology ahead. Strategic Air Command needed an aircraft that could fly at Mach 2 plus speeds at high altitude and then, critically, perform a supersonic, low level dash to the target. That aircraft turned out to be the FB-111. B-52s remained SAC's long-range bomber deterrent until a suitable replacement appeared. A point that would be more than 20 years in the future when the B-1B started to take over that role.
With the announcement of the FB-111 in December 1965, it was envisioned that SAC would possess a total of 263 FB-111 aircraft (20 of which would be trainers). This total was eventually reduced to only 76 amid the ascendancy of the Inter-Continental Ballistic Missile (ICBM) as SAC's main deterrent and in anticipation of the Advanced Manned Strategic Aircraft (AMSA) project (the B-1 bomber). Bad publicity and cost over runs also 'dinged' the FB-111 program. Initial flight of the General Dynamics FB-111A took place in July 1967, with the first production aircraft delivered in August 1968. Production of the FB-111 lasted for 3 years (August 1968 - June 1971).
Compared to the F-111A/E, each wing saw lengthening by 3.5 ft. (a little over one meter) and the landing gear was strengthened to handle a greater take off weight. It also incorporated more powerful engines with 20,350 lbs (90.52 kN) of thrust each rather than 18,500 pounds (82.29 kN) thrust. New avionics, including a astronavigation system (ANS) accurate to several hundred feet (~ 100 m) were fitted. This system could even work during daylight. For a time before a working global positioning system (GPS) this accuracy was remarkably good and it was needed for transiting regions devoid of navigational cues like the polar route - the shortest path to targets in Russia. Able to carry six 600 US gallon (2270 l) drop tanks to extend range - a configuration that was rarely if ever utilized in active service - the FB-111 still needed additional refueling and basing in certain areas closer to the enemy.
Principal weapons included nuclear gravity bombs, like the B43, B61, and the B83, and Short Range Attack Missiles (SRAMs). Also, 24 conventional bombs could be carried when desired. The SAC paint scheme of dark green and gray led to the unofficial nickname 'Dark Vark' for these planes. For info on a 'Super FB-111' click here
| Designation | FB-111A |
|---|---|
| Type | Strategic medium-range bomber |
| Crew | Two, pilot and navigator (side by side) |
| Contractor | General Dynamics |
| First Flight | 30 July 1967 |
| Production | 76 built between August 1968 and June 1971 |
| Propulsion | Two Pratt & Whitney TF30-P7 afterburning turbofans |
| Engine thrust | 20,350 lbs (90.52 kN) thrust each |
| Weight, empty | 45,200 lbs (20500 kg) |
| Weight, basic | 49,090 lbs (22680 kg) |
| Weight, combat | 70,380 lbs (31920 kg) |
| Weight, max. t/o | 114,300 lbs (51850 kg) |
| Wing Span | 70 ft (21.3 m) (fully extended wings) |
| Wing Span | 33 ft, 11 in (10.4 m) (fully swept wings) |
| Wing Area | 550.00 sq ft (51 sq m) |
| Length | 75 ft 6 in (23 m) |
| Height | 17 ft 2 in (5.2 m) |
| Service Ceiling | 60,000 ft (18300 m) |
| Climb rate | 23,418 ft/min (7140 m/min) |
| Speed, max. | 1,675 mph (2700 km/h) (Mach 2.2) |
| Speed, cruise | 571 mph (920 km/h) |
| Range | 2,920 miles (4700 km) (non-refueled) |
| Weapons | Nuclear gravity bombs, like the B43, B61, and the B83, SRAMs; up to 24 conventional bombs 1 |
| Weapon load | 35,500 lbs (16100 kg) in weapons bay and on wing pylons |
| 1 | Weapons also included one 20mm M61A1 cannon, usually kept in storage at air bases. |
Two 509th Bomb Wing FB-111s
"General Dynamics F-111 Aardvark (Air Vanguard)" by Peter E. Davies. Bloomsbury Publishing. Kindle Edition. 2013
"F-111 Aardvark: General Dynamics' Variable-Swept-Wing Attack Aircraft" by John Gourley. Schiffer Military. 2021
Strategic Air Command (SAC) & Aerospace Museum
March Field Air Museum
The Nuclear Information Project (Federation of American Scientists)
"A Compendium of Armaments and Military Hardware" by Christopher Chant. Routledge & Kegan Paul Books. 1987
"Aircraft Armaments Recognition" by Christopher Chant. Ian Allan Ltd. 1989
"Illustrated Encyclopedia of the World's Rockets and Missiles" by Bill Gunston. Crescent. 1979
Metric values calculated with the help of Convertworld
B61 nuclear bomb
| Designation | B43 | B61 | B83 |
|---|---|---|---|
| Type | thermonuclear bomb | thermonuclear bomb | thermonuclear bomb |
| Intended role | strategic | tactical / strategic | strategic |
| Developed by | LASL 1 | LANL 1 | LLNL 1 |
| Manufactured | 4/61 - 10/65 | 10/66 - early 90s | 6/83 - 1991 |
| Retired | (early Mods) began 12/72, last 4/91 | (early Mods) retired 70s - 80s | To be retired 2 |
| Production | 1000 (all Mods) | 3150 (all Mods) | 650 (all Mods) |
| Warhead | Mk-43 | Mk-61 | Mk-83 |
| Yield | 70 kT to 1 Megaton | (Mod 7) 10 - 340 kilotons | low kT to 1.2 MT |
| PAL Cat 3 | (Mod 2) B | (Mod 7) D | D |
| Fuzing | airburst or contact | airburst or contact | airburst or contact |
| Delivery | F/F 4 or retarded, 5 laydown 6 | F/F 4 or retarded, 5 laydown 6 | F/F 4 or retarded, 5 laydown 6 |
| Accuracy | < 600 ft ? (180 m) | < 600 ft (180 m) | < 600 ft (180 m) |
| Parachutes | 1x4 ft (1.2 m), 1x23 ft (7 m) ribbon 7 | 1x17 ft (5 m) or 1x24 ft (7.3 m) ribbon 7 | 3x4 ft (1.2 m), 1x46 ft (14 m); 1x5 ft (1.5 m), 1x46 ft (14 m) |
| Features | available in five yields | release height: low as 50 ft (15 m) DAY (Dial-A-Yield) FUFO: Full Fuzing Options | release height: low as 150 ft (45 m) DAY (Dial-A-Yield) FUFO: Full Fuzing Options |
| Weight | 2,060 - 2,125 lbs (935 - 960 kg) | 695 - 716 lbs (315 - 325 kg) | 2,408 lbs (1090 kg) |
| Length | 12 ft 6 in - 13 ft 8 in (3.81 - 4.17 m) | 11 ft 9.5 in (3.59 m) 8 | 12 ft 1 in (3.68 m) |
| Diameter | 18 in (0.46 m) | 13.4 in (0.34 m) | 18 in (0.46 m) |
| 1 | LASL (Los Alamos Scientific Laboratory); LANL (Los Alamos National Laboratory); LLNL (Lawrence Livermore National Laboratory). |
| 2 | B83 to be retired under the 2022 Nuclear Policy Review. |
| 3 | PAL Cat denotes the Permissive Action Link (PAL) Category of the bomb (A - F). |
| 4 | F/F (Free Fall). |
| 5 | Retarded delivery means a parachute slows down the bomb as it falls, allowing the aircraft to escape the weapon's blast. |
| 6 | Laydown is a high / supersonic speed, low-level release over the target. |
| 7 | Ribbon parachutes resist ripping and bursting at high / supersonic speeds. |
| 8 | B61 length includes tail fins; body length alone equals 10 ft 10.75 in (3.32 m). |
data from https://nuclearweaponarchive.org/index.html
For more info on the latest B61 nuclear weapon including its possible use in bunker busting
The Short Range Attack Missile or SRAM is a rocket propelled air-to-ground missile with a nuclear warhead. It has the great advantage over free fall nuclear bombs of allowing a launch aircraft to standoff and fire at a target rather than overflying it. Considered a replacement for the much larger AGM-28 'Hound Dog' missile, the Boeing Company received an Air Force contract for developing and building the Short Range Attack Missile on 31 October 1966. The first launch of a SRAM took place on 29 July 1969, and it entered service in 1972. A basic inertial guidance system meant an accuracy of approx. CEP 1400 ft (430 m) - adequate considering we're dealing with a ~200 kiloton nuclear weapon. Although primarily intended to take out defensive installations, like SAM sites, the SRAM could also be used against strategic targets. Range of the weapon depended on launch altitude but could be over 100 miles (160 km). It had a maximum speed of Mach 3+ and a weight of about 2,240 lbs (1010 kg). For full specifications click on this link or scroll down.
The weapon has several flight profiles available: semi-ballistic, terrain following by radar altimeter, ballistic pop-up followed by terrain following, and a combination of terrain following and inertial guidance. In addition, any of these flight profiles can factor in pre-set 180 degree course changes. All of this made the SRAM, who's radar cross section (RCS) is already small, even harder to detect and intercept.
B-52G and H models could carry 20 Short Range Attack Missiles, six on each of two wing pylons and eight on a rotary launcher in the aft bomb bay while the FB-111A could haul a maximum of six SRAMs, two in the bomb bay and four on underwing pylons. Finally, the B-1B bomber has the capacity to carry 24 SRAMs internally, using three eight round rotary launchers.
The first B-52 unit to to become operational with the SRAM was the 42nd Bomb Wing (B-52G), Loring AFB, Maine, on 15 September 1972. The 509th Bomb Wing (FB-111), Pease AFB, New Hampshire became the first FB-111 unit operational with the weapon on 1 January 1973. On 20 August 1975, the last of the 1500 SRAMs produced were delivered to SAC's 320th Bombardment Wing, Mather AFB, California.
Concerns about degradation of the rocket propellant inside the SRAMs and lack of a fire resistance pit in its nuclear warhead led to the weapon being withdrawn from service in June of 1990. Work on the AGM-69B, an upgraded AGM-69A with a new Thiokol liquid propellant rocket, was canceled in 1977. Later, in December 1986, Boeing was selected to produce a new SRAM (the AGM-131A SRAM II). Click on the link for more info about the SRAM II or scroll down.
| Name | SRAM (Short Range Attack Missile) |
|---|---|
| Designation | AGM-69A |
| Type | rocket propelled air-to-ground nuclear missile |
| Contractor | Boeing |
| First Launch | 29 July 1969 |
| In Service | 1972 - 1990 |
| Production | 1500 built |
| Propulsion | one Lockheed SR75-LP-1 two-stage solid-fuel rocket |
| Warhead | W-69 nuclear warhead |
| Yield | 170 - 200 kT |
| Fuzing | airburst and contact |
| Guidance | Singer-Kearfott KT-76 inertial plus terrain-avoidance radar altimeter |
| Features | multiple flight profiles optional 180 degree course changes can be pre-set |
| Weight | 2,240 lbs (1010 kg) |
| Length | 14 ft (4.27 m) 1 |
| Diameter | 17.5 in (0.44 m) |
| Span | 3 small tail fins set 120 degrees apart |
| Speed | Mach 2.8 to Mach 3.2 |
| Range | 100 - 137.5 miles (160 - 220 km) high-altitude launch 35 - 50 miles (55 - 80 km) low-altitude launch |
| Accuracy | CEP 1400 ft (430 m) 2 |
| 1 | 15 ft 10 in (4.83 m) with tail fairing, used to reduce drag when the SRAM is carried externally. |
| 2 | CEP stands for Circular Error Probable. a measure of weapon accuracy, often defined as the radius of a circle in which 50% of the weapons fired will impact. |
SRAM missiles (inert)
In December 1986 Boeing was tasked with developing a follow on to the Short Range Attack Missile (SRAM). Designated AGM-131A SRAM II, it featured a 200 kiloton W-89 nuclear warhead, digitally-controlled with significant safety features: a Fire Resistant Pit (FRP), the use of Insensitive High Explosives (IHE) and a Permissive Action Link (PAL) D Category. The new SRAM reached full-scale development in 1987. About 2/3 the size of the AGM-69A Short Range Attack Missile, the AGM-131A had an advanced two-pulse solid fuel rocket motor, and improved guidance with a laser ring-gyro inertial navigation system. The airframe, made of mostly composite materials, enhanced the missile's low-observable characteristics (stealth). Although, it was expected to enter service in 1992 the SRAM II was canceled in 1991 as part of an arms control initiative. There were also production problems with the missile's motor, according to a USAF fact sheet.
The Nuclear Information Project (Federation of American Scientists)
"Aircraft Armaments Recognition" by Christopher Chant. Ian Allan Ltd. 1989
SRAM II missile at the NMUSAF *
* National Museum of the United States Air Force
General Dynamics had been working earlier, on a possible F-111G - a bomber variant of the F-111. This was not pursued with. In the wake of the B-1 program being canceled by President Jimmy Carter on 30 June 1977 there appeared an opening for an aircraft to fill the void. Now the company looked at a stretched and improved version of the FB-111A - the FB-111H.
Powered by two General Electric F-101 30,000 lbs (133.45 kN) thrust afterburning turbofans, 17,000 lbs (75.62 kN) thrust w/o afterburner, this was the same engine that was used with the B-1 bomber. Length went from 75 ft 6 in to 88 feet 2.5 inches, allowing an internal fuel load of 64,574 pounds (29300 kg) and doubling the size of the weapons bay. The wingspan remained the same but maximum sweep back was limited to 60 degrees instead of 72.5 degrees with the FB-111A. This means that a supersonic dash at low level would not be possible, although it still would be traveling at very high subsonic speeds. Max. speed reached Mach 2.5 at altitude and range increased by about 1,200 nm (2220 km). Empty weight rose to 51,832 pounds (23300 kg) and max. t/o weight grew to 140,000 lbs (63500 kg). Also, a maximum inflight weight of 155,000 pounds (70300 kg) could be accommodated. A 43 percent commonality of structure was maintained with the F-111A - F.
A 4-round SRAM rotary launcher or 4 - 5 nuclear bombs fit in the weapons bay, while total payload would have been 15 nuclear weapons. Considered a candidate for a Long Range Combat Aircraft (LRCA), the matter was settled in October 1981 when President Ronald Reagan announced that 100 B-1Bs were to be built.
Artist concept of lengthened, advanced FB-111, 1980
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