The Plane With No Name
The F-111: In Australia, an airplane for all seasons.
- By William Triplett
- Air & Space magazine, March 2002
(Page 4 of 8)
The Air Force soldiered on with the F-111A, which turned out to be a revolutionary aircraft, exemplifying, according to the U.S. Air Force historian Richard P. Hallion, two great aeronautical advances then under way. One was the breakthrough in high-speed flight made possible by the maturation of turbojet technology. The second was an explosive growth in the use of electronics, which led to the development of the first "systems" airplanes. "The first category of those airplanes were the air defense interceptors," says Hallion. "But the second category was the sophisticated air-to-surface attack aircraft, and coming out of that was the notion of all-weather attack. There were two great early systems airplanes in the air-to-surface arena. One was the F-111 and the other was the [U.S. Navy's] A-6."
The electronics package in the F-111 included the hair-raising terrain-following radar, built by Texas Instruments and integrated with a targeting radar, an inertial navigation system, and other sophisticated avionics. The result was an unprecedented autopilot that would enable high-speed flight at extremely low altitude at night and in all kinds of weather. The pilot and weapon systems operator could be guided with electronics to strike a target they couldn't see. At least that was the plan.
The F-111A saw its first action with the 428th Tactical Fighter Squadron in Vietnam during the spring of 1968. Three crashed within a month of the first combat sortie, killing two crews. A fourth crashed at Nellis Air Force Base in Nevada that May. The Air Force suspected that in at least two of the crashes, the cause was TFR failure. At the same time, -111s were suffering engine compressor stalls, during which airflow reverses because of pressure fluctuations at the inlet. The Air Force grounded the aircraft and, along with NASA and General Dynamics, worked to redesign the engine inlets.
The sink rate of a variable-sweep-wing aircraft on final approach was a challenge to pilots. "We lost one airplane and one crewman at Edwards Air Force Base as a result of that," says Hallion. Then during spin-and-departure trials, the test model went out of control and crashed.
The RAAF took delivery of its first F-111C in July 1968. During static testing in September, a wing failed, and General Dynamics suspended delivery of the 23 remaining aircraft.
"The F-111 was a very difficult airplane for the Air Force to deal with," says Hallion with a sigh. The critical areas were the pivot joint, where the wings attach to the fuselage, as well as a fitting called the wing-carry-through box (WCTB), wherein the loads from the wings pass through the fuselage. Hairline cracks were causing catastrophic failure of the pivot joints, while an investigation of the WCTB traced the failures to defective manufacturing. Over the next several years all USAF F-111As (and the RAAF's one C) were retrofitted with strengthened pivot joints and properly manufactured WCTBs. The compressor stalls were fixed by expanding the inlet and inserting a new adjustable inlet device that maintained proper airflow into the compressor. But the modifications were driving up the price of the aircraft, first from the original $4.5 million per unit to $6.3 million, then later much higher.
Some in Congress took to calling the F-111 "McNamara's Flying Edsel." In Australia critics disparaged it as "the Flying Opera House," linking it with the Sydney Opera House, then under construction and suffering from massive cost overruns and delays. The RAAF didn't take delivery of its remaining 23 F-111Cs until June 1973. Four were later converted for reconnaissance and designated RF-111Cs.
Even after its U.S. redeployment to Southeast Asia in the fall of 1972, bugs continued to infest the -111's avionics, but the aircraft nonetheless began to prove itself—flying in weather that kept other aircraft on the ground, hitting targets using only instruments. The Air Force flew F-111s on some 4,000 combat missions in Vietnam and lost only six aircraft.