Subject: Number 111 in the Series--General Dynamics F-111 (9 of 13)

From: [email-masked]
Date: 18 Mar 94 17:44:43 GMT

>From [email-masked]

The FB-111A was the all-weather strategic bombing version of the F-111, 
intended as an interim successor to the B-52 and B-58 of the Strategic 
Air Command.  It was initially developed as Weapon System 129A.  

The FB-111A differed from the F-111A primarily in having a longer 
fuselage (75 feet 7 inches as compared to 73 feet 5 1/2 inches) to 
accommodate the additional fuel required for its strategic mission.  
In order to provide a longer range and greater load-lifting 
capability, the FB-111A had the extended wing of the F-111B (unfolded 
span of 70 feet as compared to 63 feet).  It also had a stronger 
undercarriage and landing gear, and was powered by TF30-P-7 turbofan 
engines.  It featured the Mark IIB avionic subsystem planned for the 
F-111E, which comprised an improved F-111A attack radar, an inertial 
navigation system, digital computers, plus some advanced displays of 
the later Mark II that equipped the delayed F-111D 

The FB-111A was actually the first F-111 version to fly with the new 
Triple Plow II air intakes, beginning with the third example 
(67-0161).  The Triple Plow II intakes were mounted four inches 
farther from the airframe in order to improve the boundary layer 
"plow", and the translating cowl was replaced by a series of blow-in 
doors which fed additional air to the engines during takeoff or when 
the aircraft was moving slowly.  

The development of the FB-111A was prompted by the slow progress of 
the Advanced Manned Strategic Aircraft (AMSA) program and by fears 
that fatigue failures in the B-52 fleet might come earlier than 
expected.  A proposal to resume production of the Convair B-58 Hustler 
was rejected as being too costly.  In the spring of 1963, the Air 
Force turned to General Dynamics for a solution to its problem.  In 
November of 1963, General Dynamics responded with a suggestion for two 
strategic versions of the F-111A.  In order to hasten availability, 
the Air Force decided on June 2, 1965 that the least modified version 
was the one that they would go with.  The designation FB-111A was 
applied, which is sort of curious since the design was basically a 
modified F-111A, which would have suggested that the designation 
should have been BF-111A.  

The Air Force initially planned to order 263 FB-111As (210 to equip 14 
squadrons, plus 20 for combat crew training and the remaining 33 for 
support and testing).  It wanted them in service quickly, the first 
FB-111As being expected to be operational as early as fiscal year 
1969.  

Secretary of Defense Robert McNamara publically announced plans to 
develop the FB-111A on December 10, 1965.  However, the implementation 
of the program was postponed until February 1966, when the FB-111A had 
been added to the basic F-111A RDT&E contract and Congress had 
approved the funds.  In January of 1966, Secretary McNamara asked the 
Air Force to begin contract definition on Mark II avionics systems for 
both the FB-111A and the delayed F-111D, with maximum commonality 
being a key requirement.  The primary weapon of the FB-111A was to be 
the Boeing-designed AGM-69A Short-Range Attack Missile (SRAM).  

A modified RDT&E F-111A (serial number 63-9783) was converted as the 
prototype of the FB-111A and flew for the first time on July 30, 1967.  
It achieved Mach 2 on its first test flight.  

Pending the availability of the P-7 engine, it was decided that the 
first few FB-111As would receive P-12A engines (the USAF version of 
the Navy P-12 engine that was used in the F-111B) and these engines 
would subsequently be brought up to the P-7 configuration once the 
aircraft was in service.  

The first production FB-111A aircraft flew on July 13, 1968.  It was 
accepted by the Air Force on August 30, 1968.  A second FB-111A was 
delivered on October 25.  These two planes were powered by TF30-P-12A 
engines.  Problems with the Mark IIB avionics slowed further 
deliveries, with the Air Force not accepting its next FB-111A until 
June 23, 1969.  This aircraft featured a fully-developed Triple Plow 
II air diverter, a complete Mark IIB avionics system, and the new P-7 
engines.  

The first 6 FB-111A production aircraft were used for testing.  
Category III tests did not finish until July 31, 1972.  

A total of 263 planes was projected when the FB-111A program began.  
This was reduced to 126 on November 28, 1968 because of rising costs 
and production delays with the basic F-111 program.  The final cut 
took place on March 16, 1969, with the total FB-111A order being 
reduced to 76.  

On October 8, 1969, the 7th FB-111A entered service with the 4007th 
Combat Crew Training Squadron of the 340th Bomb Group at Carswell AFB.  
Even though the FB-111A was officially declared operational, it had 
yet to reach the combat forces.  After reaching operational 
capability, the 4007th CCTS relocated to Plattsburg and became part of 
the 380th Strategic Aerospace Wing.  

The primary offensive armament of the FB-111A was the Boeing-designed 
AGM-69A SRAM, a missile designed primarily to neutralize enemy defense 
systems such as radars, SAMs, and other anti-aircraft systems.  The 
launch weight of the SRAM was 2230 pounds, and it was powered by a 
two-pulse solid-fuel rocket motor.  Maximum speed was Mach 2.8-3.2, 
and the range varied from 35 to 105 miles, depending on the mission.  
The guidance system consists of a Singer Kearfott inertial guidance 
operating in conjunction with a Delco on-board computer.  Various 
attack trajectories could be chosen, ranging from semi-ballistic to 
terrain-following.  During an actual operational mission, the 
bombardier would selects each missile in turn, update the inertial 
guidance system, then would let the missile drop.  The rocket motor 
would then fire and accelerate the missile to Mach 3.  fast enough to 
fly and steer with body lift and three tail fins.  When the missile 
neared the target, the second propulsion stage would then ignite for 
the final run in to the target.  The SRAM carried a W6 nuclear warhead 
with an explosive yield of 200 kilotons.  

FB-111A testing of the SRAM began on March 27, 1970.  Initial test 
started poorly--in almost a year, there were only seven successes out 
of 11 launches.  However, by early 1961, the results began to get 
better, with the final score being 15 successes out 19 launches during 
the entire test series.  

In January 1971, the FB-111A achieved initial operational capability 
with the 509th Bomb Wing (393 and 715 Squadrons) based at Pease AFB in 
New Hampshire.  After many difficulties, the 509th was finally 
declared fully combat-ready in October of 1971.  The 380th Strategic 
Aerospace Wing (528 and 529 Squadrons, plus the 4007th Combat Crew 
Training Squadron) at Plattsburg AFB in New York became combat ready 
in 1972.  These were the only two SAC wings to receive the FB-111A.  

The last production FB-111A (68-0291) was delivered to SAC on June 30, 
1971.  

The FB-111A could carry two AGM-69A SRAMs in the internal weapons bay 
along with two more on the inner underwing pylons.  Typically, four 
600-US gallon drop tanks were carried on the outermost underwing 
pylons, although the SRAMS carried underneath the innermost underwing 
pylons could be replaced by another pair of 600-gallon drop tanks, 
bringing the total number of drop tanks to six.  The non-swiveling 
outer pylons are intended for subsonic flight only and are jettisoned 
when wing sweep exceeds 26 degrees.  Alternatively, up to 24 750-pound 
conventional bombs could be carried externally.  The FB-111A could 
also carry six gravity nuclear weapons or a B77 nuclear bomb.  A total 
offensive load of 35,500 pounds could be carried.  

The FB-111A carries the APQ-144 forward-looking attack radar, which 
was derived from the APQ-113 of the F-111A.  It adds a beacon mode, a 
photo recording capability, and a north-oriented display.  

Landing gear malfunctions persisted throughout mid-1971 and were 
finally solved by a simple field modification.  In late 1971, weapons 
delivery was still marginal, reflecting failures in the inertial 
navigation system.  There were some problems with engine flameouts 
following use of the afterburner, these being probably caused by 
moisture in the engine sensing line.  

In April 1972, new SRAM-carrying equipment was installed on the 
FB-111A.  

In November 1970, the FB-111A took top honors in bombing and 
navigation during SAC's competition at McCoy AFB in Florida.  The 
first overseas deployment of the FB-111A was the entrance of two Pease 
FB-111As in a Royal Air Force bombing and navigation meet at RAF 
Marham.  

As the Rockwell B-1B Lancer came into service, the FB-111A became 
redundant to SAC needs, and most surviving FB-111As were converted 
into ground attack configuration and assigned to training units 
operating out of Cannon AFB in California.  During 1988, the 
designation F-111G was adopted for the FB-111As that were to be 
converted eventually to serve in the tactical role when displaced from 
SAC.  

In June of 1990, the SRAM missiles were removed from the inventory 
because of safety concerns regarding the integrity of their W69 
nuclear warheads in the event of a fire.  After that, the FB-111As 
stood alert with only gravity bombs.  

Serials of the FB-111A: 

67-0159/0163 
67-7192/7196 
68-0239/0202 
69-6503/6514 

Specification of the FB-111A: 

Two Pratt & Whitney TF30-P-7 turbofans, 12,500 lb.s.t. dry and 20,350 
lb.s.t. with afterburner.  Maximum speed (clean): 1453 mph at 50,000 
feet, 1320 mph at 36,000 feet, 838 mph at sea level.  Initial climb 
rate (clean) 23,418 feet per minute.  Service ceiling: 50,263 feet.  
Range: 2500 miles with four SRAMs and internal fuel only.  Maximum 
ferry range: 4786 miles with six 600-US gall. auxiliary fuel tanks 
mounted on underwing pylons.  Weights: 47,980 pounds empty, 119,250 
pounds gross.  Dimensions: Wingspan 70 feet 0 inches (minimum sweep), 
33 feet 11 inches (maximum sweep), length 73 feet 6 inches, height 17 
feet 0 inches.  Internal fuel capacity of 5010 US gallons.  With six 
600 US gallon underwing drop tanks, a total of 9223 US gallons of fuel 
can be carried.  Armed with up to six Boeing AGM-69A SRAMs on external 
pylons or in internal weapons bay, or a conventional ordnance load of 
up to 37,500 pounds of bombs, rockets, or fuel tanks.  

Sources:

  United States Military Aircraft Since 1909, Gordon Swanborough and
  Peter M. Bowers, Smithsonian, 1989.

  General Dynamics Aircraft and their Predecessors, John Wegg, 
  Naval Institute Press, 1990.

  Post-World War II Fighters: 1945-1973, Marcelle Size Knaac,
  Office of Air Force History, 1986.

  The American Fighter, Enzo Angelucci and Peter Bowers,
  Orion, 1987.

  The World Guide to Combat Planes, William Green, Macdonald, 1966. 

  Modern Air Combat, Bill Gunston and Mike Spick, Crescent Books, 1983.

  The Illustrated Encyclopedia of Aircraft Armament, Bill Gunston,
  Orion, 1988. 

  Flying the Frontiers--NACA and NASA Experimental Aircraft, Arthur
  Pearcy, Naval Institute Press, 1993.

  F-111 Aardvark--USAF's Ultimate Strike Aircraft, Tony Thornborough,
  Osprey Aerospace, 1993.

  F-111 Aardvark, Hans Halberstadt, Specialty Press, 1992.

Joe Baugher		AT&T Bell Laboratories   	
2000 North Naperville Road      Naperville, Illinois 60566-7033