The Plane With No Name
The F-111: In Australia, an airplane for all seasons.
- By William Triplett
- Air & Space magazine, March 2002
IT BEGINS WITH THE PUSH, USUALLY AT, say, 20,000 feet and maybe 50 miles from the target. The pilot runs through a checklist with the right-seater, then throws a switch on the left side of his flight control panel, engaging the terrain-following radar.
The TFR noses the airplane over into a 10-degree, half-G dive, hurtling aircraft and crew toward the ground at more than 8,000 feet a minute.
One of the first aircraft to be equipped with terrain-following radar was the F-111, the swing-wing tactical fighter-bomber that made prime contractor General Dynamics infamous for a while in the 1960s. When it started service with the U.S. Air Force in 1967, it followed the terrain of the Nevada desert near Nellis Air Force Base. Today the terrain is the scrubby hill country around Royal Australian Air Force Base Amberley in the Queensland province of Australia. The RAAF Strike Reconnaissance Group at Amberley is now the only combat unit in the world operating F-111s.
In the dive, the pilot throttles back a little to keep from going supersonic and then, with a pistol-grip control under the left canopy railing, sweeps the wings back to 44 degrees.
The F-111 was also the first operational aircraft with variable-geometry wings. When configured with the minimum sweep, 16 degrees, the wings provide enough lift for a heavily armed fighter to take off and land on short airstrips. With the wings fully swept at 72.5 degrees, the F-111 is a hot rod capable of Mach 2.5. At cruise altitude, the pilot typically sets the wings at 26 degrees of sweep for maximum range and fuel efficiency.
Once the aircraft has descended to 5,000 feet, the ride gets more interesting. The TFR pushes the nose down even more, to 12 degrees, increasing rate of descent to 12,000 feet a minute. "A bit counter-intuitive, isn't it?" says Air Commodore Dave Dunlop, head of the Strike Reconnaissance Group at Amberley, where all 35 of the RAAF's F-111s are based. "Very unsettling the first time you do it," says Squadron Leader Matt Sibree, one of the younger pilots. Apart from watching instruments to make sure things are operating as they should, the pilot is just along for the ride—as is the navigator, the RAAF's term for the right-seater. In the U.S. Air Force it's a weapon systems operator, or WSO (pronounced "wizzo"), who also has navigation duties, just as RAAF navs also operate weapon systems.
The TFR finally levels the aircraft at a pre-determined altitude, usually at about 1,000 feet. The crew can then begin "stepping down" at 200-foot increments to as low as 200 feet for the run to the target. The twin turbofans are propelling the aircraft at between 600 and 700 mph. The pilot sweeps the wings accordingly—10 percent of airspeed in knots, meaning anywhere from 51 to 60 degrees. With a sweep of greater than 45 degrees, though, the spoilers can't be used, thus severely limiting the amount of roll that can be introduced.
It's a wild ride—something that could also be said of the F-111's entire career.
One-elevens served 30 years in the U.S. Air Force, eventually distinguishing themselves in several roles, but their reputation has never fully recovered from the controversy surrounding their tragic introduction. The aircraft may be unique among U.S. fighters in that it was not christened with an official nickname—a name like "Super Sabre" or "Thunderchief," the names of the F-100 and F-105, which the F-111 was designed to replace. When the U.S. Air Force retired its last -111s in 1996, officials at the ceremony finally bestowed on the airplane the name pilots had been unofficially calling it for years—"Aardvark," chosen because the airplane's extended nose makes it resemble the long-snouted pig-like African creature.
Aussies, who take pride in their tradition of plain talk, simply call it "Pig." It is a term of endearment, spoken with great respect because in Australia, as in its later years in U.S. service, the –111 has matured into the role it was designed to fill.
"So what's the airplane good for?" asks RAAF Wing Commander and veteran Pig driver David "Doc" Millar. He's leading a briefing at Amberley for novice crews. A giant map of Australia flanks him at the front of the room. On it are several large circles whose centers are RAAF air bases dotting Australia's northern coastal areas, and the circles—each representing the 3,500-mile operating range of combat-ready F-111s—stretch hugely toward Southeast Asia. Millar nods toward the circles, saying with pride, "And that, gentlemen, is why we're still flying a jet that was designed in 1963. Nothing else can do that."
In training exercises, F-111s have carried 8,000 pounds of bombs for 1,500 miles—at low level for 300 of them—without airborne refueling. They can do it at any time of day or night and in any kind of weather. Millar's right. Nothing else can. But why did Australia ever feel a need for such capability?
In the years following World War II, as the British government began withdrawing from its former Asian colonies, Western leaders fretted over communist expansionism. The fretting rose to the level of military action in June 1948, when Chinese communists in the Malay peninsula murdered three wealthy rubber plantation owners, setting off a terrorist campaign to overthrow the British-supported government there. The RAAF joined in the counterattack from an air base in Singapore, and the fighting continued sporadically until 1960.
By that time, Western thinking had crystallized into the so-called domino theory, which held that one country after another would fall to communism if no one challenged it. Australia was nervous about neighboring Indonesia, whose president, Achmad Sukarno, was vague about whether he'd oppose or welcome communist influence. (Indonesia's political instability resulted in a failed 1965 coup dramatized in the film The Year of Living Dangerously.)
In a grab for headlines, Australian politician Arthur Calwell claimed in 1963 that the Indonesian air force could bomb almost any city in Australia and that the RAAF had no capability to reciprocate. Although the remark was primarily political exploitation, it struck a nerve. The RAAF's strategic bomber at the time, the English Electric Canberra, was an old design—the first jet bomber to be manufactured in Great Britain—and it had limited range. From an Australian base, it was unable to reach Indonesia or any other part of Southeast Asia, where communism was beginning to get a foothold.
"Replacing the Canberra had been the RAAF's top priority for a number of years," wrote RAAF historian Alan Stephens in the book Going Solo: The Royal Australian Air Force 1946–1971. "In a reflection of classic air power doctrine," Stephens comments today, "the need for a new strike/reconnaissance aircraft was expressed in terms of taking the initiative in the air by destroying the enemy's air force on the ground, then turning the RAAF's offensive air power against other targets, both strategically and in direct support of the army and navy."
The strategy called for an aircraft with an attack capability that was both versatile and precise. At first the RAAF considered buying the TSR.2, a new warplane the British Aircraft Corporation was developing. But the TSR.2 never went into production, and the Aussies turned their attention to the F-111.
Today any threat to Australia is still theoretical, but the RAAF continues to look warily toward the north. "Because any threat to Australia would likely come through the sea and archipelagic region to the north, we need a long-range, multi-role capability to operate in that environment," says Wing Commander Brian Walsh of the air attaché staff at the Australian embassy in Washington, D.C.
Says Stephens: "It's also noteworthy that when the Interfet [United Nations peacekeeping] force deployed to East Timor in 1999, a detachment of F-111s was sent to the RAAF's base at Tindal, near Darwin. While the aircraft weren't used, the message was crystal clear and was understood by those for whom it was intended."
"Being an island continent, most of our defense is based on the perception that any potential enemy would have to cross the sea to get to us," Dunlop says. Thus the RAAF wanted a few custom features on their -111s, beginning with anti-ship weaponry. They also liked the longer wings on a Navy version, the F-111B, and a fighter-bomber variant, the FB-111A. General Dynamics designed the F-111C exclusively for the RAAF. It was the only model ever to be capable of firing a Harpoon anti-ship missile. In October 1963, when the aircraft was still being designed, the RAAF agreed to pay $100 million for 24 of them; the service recently announced that it plans to continue operating its fleet in both strike and reconnaissance roles until the year 2020. Few would have predicted that the F-111 was destined for such a long career.
Near the end of the 1950s the USAF Tactical Air Command put together its requirements for a future attack aircraft. TAC wanted an airplane that could do Mach 2.5 at altitude and Mach 1.2 at low level, where, if necessary, it could fly 400 miles without slowing down. It would have to be able to take off and land on airstrips as short as 3,000 feet and to fly un-refueled across the Atlantic Ocean with an ordnance load of up to 30,000 pounds.
Meanwhile, the U.S. Navy also happened to need a new fighter—to be based on aircraft carriers and serve as fleet defense. The coincidence turned out to be one of the most unhappy and expensive chapters in the history of interservice collaboration. Shortly after John F. Kennedy took office in 1961, Secretary of Defense Robert McNamara tried to save the new administration money by ordering the Air Force and the Navy to develop one aircraft that would carry out both missions. In 1969 the Navy finally abandoned the joint venture, dubbed TFX for Tactical Fighter Experimental; by then, McNamara's idea had ended up wasting $377 million.
From the start, the two services banged heads over just about everything. The Navy wanted side-by-side seating for the two-man crew, long-range radar, long loiter capability at upper altitudes and subsonic speeds, and a gross weight of under 50,000 pounds for carrier operations. The Air Force wanted tandem seating and, focusing on low-level, supersonic capabilities, some sort of terrain-reading radar—not yet invented—and a gross weight of 75,000 pounds. The only point of agreement was the need for a variable-geometry, or swing, wing: Both services wanted maximum lift for short takeoffs, along with high-speed capability once airborne. (Although the F-111 was the first operational aircraft to use a variable-geometry wing, the concept was not new. The Bell X-5 experimental aircraft tested the configuration in the early 1950s, and those tests were based on research reports "imported" from Germany at the end of World War II.)
General Dynamics built the F-111A for the Air Force, and Grumman built the F-111B for the Navy. Both versions had the variable-geometry wing, turbofan engines, side-by-side seating, and a crew escape module (instead of the usual ejection seats). But only seven Bs ended up being built. The Navy withdrew from the program after concluding that the aircraft could never be brought under weight restrictions for carriers. But having gathered experience in producing swing-wing aircraft, Grumman later embarked with the Navy upon another program that proved far more successful—the F-14 Tomcat.
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.
Once outfitted in the 1980s with new avionics—specifically the Pave Tack targeting system, which uses a high-quality infrared video camera to acquire targets and an integrated laser designator to guide bombs to them—the F-111 could live up to its original promise. Of the 8,000 laser-guided bombs that the Air Force dropped during the 1991 Persian Gulf war, about half were dropped from F-111s. One-eleven crews also perfected the technique known as "consecutive miracles," in which one laser-guided bomb blows open the front of a hardened shelter and another, coming seconds behind, slams deep inside for a direct internal hit.
In the mid-1990s the RAAF bought 15 F-111Gs—formerly a nuclear-capable version built for the U.S. Strategic Air Command, which had originally designated them FB-111s. The service had also acquired four A models and converted them to Cs to replace aircraft that had crashed. One of these, in Australian service as A8-109, was flown on a number of missions to North Vietnam, according to Doc Millar, and suffered battle damage to the fin. "It was described in early F-111 literature as a bit of a dog," says Millar, "but in current RAAF service it is one of the best aircraft in the fleet." Of the total 43 F-111s acquired, 35 remain in the RAAF's fleet: 17 Cs, 14 Gs, and the four recce Pigs, all flown by the two squadrons of the Strike Reconnaissance Group.
Crews love the airplane. They unanimously swear by the smooth ride of the -111 at low level, comparing it to a Cadillac on air. "At 200 feet and 600 knots in an F-18, you know it," says RAAF Group Captain Geoff Brown, a strapping older pilot who's relatively new to the F-111. "It's bumpy and the jet doesn't like it. But it's a great ride in a one-eleven—the most comfortable thing I've ever flown so low to the ground."
"It almost seems like the Earth is moving beneath the aircraft, rather than the other way around," says Jim Rotramel, a former U.S. Air Force WSO. "The things that stick with you are the impressions. Flying down a steep valley in the Scottish highlands, telling the pilot that I'm seeing in the radar high terrain on his side of the airplane and him craning his neck way up to see where the ridge stopped and the stars started."
A daylight run to a target can also be memorable. The TFR sports a pair of miniature radar dishes in the radome that scope 15 miles in the distance and then inform the autopilot of obstacles to avoid. Laterally, however, those dishes are only interested in what stands within four degrees of the aircraft's flight path. Trees and towers often whoosh past, only a matter of feet from the wingtips.
Night runs are therefore less distracting, unless you happen to be flying in one of Australia's southern test ranges, which are scored by deep gullies and canyons. "There are a couple of routes there where you can drop down into a gully and have a reasonably steep face next to you," says Dunlop. "The TFR doesn't see it. But out of the corner of your eye you'll catch the rotating beacon being reflected off the cliff side, and that'll get your attention, believe me." (Dunlop once flew with a navigator who, later asked by a local reporter what the crew does when the TFR takes over, replied, "We watch the goddam thing to make sure it doesn't kill us.")
The nav, meanwhile, is "in the feedbag"—head down, eyes glued to the multifunctional display, working to line up the target with the crosshairs of the attack radar, which can see some 30 miles ahead. "It can be nerve-wracking," says Aroha Fifield, one of the RAAF's growing numbers of female navs. Fifield, who is 23, has a bright, friendly smile that you would never associate with the ability to put a 1,000-pound laser-guided bomb in your lap from five miles away.
A toss—essentially lofting a laser-guided bomb—wracks more nerves than other attack profiles because, Fifield notes, "there's less time. You work the attack radar all the way up until you clear the pilot to release the weapon." The pilot then goes into "pedal-pull-pickle" mode—that is, disengaging, or "pedaling off," the TFR in order to pull the aircraft into a hair-flattening 25-degree, 600-mph, 4-G climb. The pilot then hits the "pickle button," which clears the weapon system to automatically release the bomb—usually about five seconds after the climb begins.
With the bomb now airborne, the hardest and most dangerous work has to be undertaken. The nav has at most 30 seconds before the bomb hits the ground. All his or her attention must be focused on the instruments: the infrared scanner to find the target, and the aircraft's laser, which must be held on the target until the bomb hits. All the while the pilot is still climbing, and the aircraft, now also banking as much as 90 degrees, is highly vulnerable to ground fire or air attack. "But it's the busiest time for flying the aircraft," says pilot Matt Sibree, "so there's no time really to think about it."
The job is tougher at night. Forty percent of the Strike Reconnaissance Group's training missions are low-level night sorties. Night attacks require "absolute faith in instruments, computers, and terrain-following radar," says Doc Millar. They also demand split-second coordination between pilot and navigator during the run to the target, when the pilot is monitoring the TFR and principal flight instruments and the navigator is in the feedbag. "Each has to know when to expect 'climb' [or] 'dive' commands from the TFR and what to expect from each other," Millar says. "This is before you add the complexity of formation, ground-based air defenses, air threats, weather, et cetera."
The complexities can lead to what air crews call "task saturation," something several American crews of the 48th Tactical Fighter Wing experienced in April 1986 during the first offensive air operation conducted by the U.S. Air Force since the Vietnam War. Stationed at Lakenheath Air Base near London, the 48th provided an attack force for a U.S. raid on Libya, which was a retaliation for Libyan-sponsored terrorism against the United States. Of the 20 F-111s that attacked, only four scored hits. Though one aircraft was lost (cause unknown) and the raid failed to kill Libyan leader Muammar Qaddhafi, it clearly caused him to lower his profile and turn down the volume of his inflammatory anti-American rhetoric. An unpublished account of the raid (the author requested anonymity) suggests what an F-111 cockpit is like during combat:
"Remit 32 [the aircraft's call sign] had a very experienced pilot paired with a relatively new but promising WSO. The spectacle of massive quantities of anti-aircraft artillery, surface-to-air missiles flying one way, HARM [high-speed anti-radiation] missiles fired by Navy A-7Es in response flying the other way, and the unexpected use of parachute flares by the Libyans, turning night into day, rattled the WSO. When the pilot realized they had gone too far without beginning their toss maneuver, they aborted their bombing run and roared across Tripoli at rooftop level.
"Remit 33 had a moderately experienced pilot and a highly experienced WSO. Without functioning TFR, they approached the target at 1,000 feet, using their radar altimeter until the parachute flares made it possible to fly visually. Then their Pave Tack pod malfunctioned, so the WSO did what WSOs had done before they had Pave Tack pods. He did a radar toss, which put their bombs squarely in the barracks courtyard, although they didn't cause any significant damage. The malfunctioning Pave Tack pod did manage to capture the launch of an SA-8 missile at these intrepid aviators, which impressed them to no end when they saw it during their debrief."
Maintaining "situational awareness" is the most crucial survival skill in combat and the one that RAAF training most emphasizes. It means that every moment, pilot and navigator together have a clear picture of the terrain, obstacles, and threats.
Some crew members would prefer tandem seating to make it easier to see threats from behind. But the majority of pilots see advantages to having someone next to you. Side-by-side seating offers fast visual communications about actions that would otherwise have to be confirmed verbally and thus take more time when time is extremely tight and concentration on systems vital.
"[Low-level night attack] is probably the most dangerous and complex form of aviation after night carrier operations," says Millar. "We have killed five percent of our air crew over the years in this flight regime."
In 28 years the RAAF has lost eight -111s, five in fatal crashes. The last four were at night and involved the military euphemism "controlled flight into terrain." "One went in at a 40-degree angle at 500 knots," says an RAAF pilot who asked not to be identified. "Not a pretty sight."
Though investigations haven't yielded conclusive proof of what caused any of the -111 crashes, Millar says the Strike Reconnaissance Group believes all were the result of human error, either "loss of situational awareness or failure of crew coordination." The group has since started a new program, Crew Resource Management Training, to improve crew coordination. And before any mission takes off, a complete risk assessment of the flight profile is mandatory, including reviews of technical and operational airworthiness.
Because of the advanced age of the fleet, ensuring airworthiness is a challenge for the SRG's maintenance personnel. The wing pivot points and the wing-carry-through boxes are presenting problems again: Although General Dynamics corrected the earlier weaknesses, the steel is starting to show its age. RAAF mechanics say it's a low-carbon alloy; despite high tensile strength, it's very brittle and prone to corrode over time.
Given the swing-wing design (that is, no wing spars to distribute loads, as a conventional aircraft would have), the loads are heaviest on the areas of the wings nearest the pivots and the WCTB. As the steel ages, those wing areas are more susceptible to stress cracks. To prevent that, mechanics have to tear down a wing (first allowing its fuel cells to dry completely). Then with a small piece of 320-bit aluminum oxide paper on the end of a finger, they reach inside and scratch away, re-profiling internal support assemblies to ease the loads on the area. "You usually spend a couple days just on one area," says a wing shop mechanic.
Other maintenance headaches involve air ducts, which are mounted outside the landing gear housing but with the bolts mounted inside the housing. The ducts break frequently and need to be replaced. "To get at them, you stand on the speed brake, put your arm through [the gear assembly], and twist around, and you're turning blind back there," says Sergeant Michael Tenaglia, who maintains engines and airframes. "You can't see it because your back's to it, so you hold a mirror up and look back over your shoulder."
Replacement parts aren't always available. Even though the RAAF spent about $100 million to acquire spares from the U.S. Air Force after the Americans retired their fleet, maintenance crews have sometimes had to refurbish old parts and have also cannibalized five F-111Gs to keep the rest of the fleet flying.
Avionics too show their age. The TFR, now in its third generation of technology, still fritzes out occasionally. And while the C models are now equipped with nearly infallible GPS receivers, the Gs still use inertial navigation, the software for which frequently needs updating, when it doesn't fail altogether.
Yet for a country that spends $6.9 billion—less than two percent of its gross domestic product, according to most recent figures—on its military, it is far cheaper to maintain an older aircraft than to replace it with something new, which would cost billions of dollars. Besides, says Dunlop, as well as about a dozen other RAAF officers, what else is out there?
Nothing like the F-111. Not really maneuverable enough to be called a fighter and several tons short of a big bomber's carrying capacity, the -111 nevertheless has its own special set of capabilities. Jim Rotramel puts it in perspective: "During my [final] flight I wanted to see how far we could go at low level, so we zig-zagged across the width of the state of New Mexico for an hour and a half at 550 mph. Our internal fuel weighed more than a combat-loaded F-16."
No wonder it was tough to find the F-111 an appropriate name.