Up, Up, and Away: The Brief, Turbulent History of France’s Ill-Fated Mercure Jet

Post originally Published December 29, 2023 || Last Updated December 30, 2023

See how everyone can now afford to fly Business Class and book 5 Star Hotels with Mighty Travels Premium! Get started for free.

Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - A Supersonic Dream Deferred

The 1960s was a heady time for aviation, as the nascent jet age fueled visions of a future where supersonic air travel would shrink the world. France shared in this dream, embarking on an ambitious project to build its own Concorde-like supersonic airliner. This noble venture aimed to propel France into the supersonic era, restoring national pride after the country had lost the initial race to break the sound barrier.

Alas, that gallic supersonic daydream quickly met the cold reality of spiraling costs and technical challenges. The story of France's ill-fated Mercure jet is one of big dreams giving way to insurmountable obstacles.
It all started hopefully enough. In 1964, the French government awarded contracts to Sud Aviation and Breguet to begin development of a new supersonic transport (SST) aircraft. This sleek plane would fly 150 passengers at more than twice the speed of sound, cutting travel times in half. Jet-setters would be whisked between Paris and New York in just 2.5 hours.

The yet-unnamed Mercure jet promised to be the Concorde's main rival, endowing France with lucrative aviation leadership and export prospects. As a bonus, it would provide some sorely needed jobs in the country's struggling aerospace sector.

But soon problems emerged. Like Concorde, the Mercure encountered endless design tweaks and ballooning costs. There were disputes over the complex swing-wing mechanism needed for supersonic and subsonic flight. Engine development lagged, partly due to lack of funding.

Sud Aviation and Breguet merged to form Aérospatiale in 1970, hoping consolidation would boost efficiency. But progress remained slow, and the program kept going over budget. An oil crisis later in the decade made economic conditions even worse.
With development costs spiraling toward $3 billion, the French government had poured in too much money to quit. But trying to attract other backers, it found little enthusiasm abroad for an unproven supersonic gamble.
Technical troubles mounted too. Wind tunnel and flight tests revealed stability issues requiring substantial airframe redesigns. All the setbacks pushed the projected maiden flight back — first from 1973 to 1975, then 1978, and eventually into the 1980s.

The aborted Mercure left a legacy of lessons about the extreme difficulty of supersonic design. Its swing-wing mechanisms later found use in Dassault's Rafale fighter jet. But France's dream of an SST to call its own slipped away, as Concorde went on to take that spotlight alone.

What else is in this post?

  1. Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - A Supersonic Dream Deferred
  2. Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - Early Promises Fall Short
  3. Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - Beset By Delays and Setbacks
  4. Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - Technical Troubles Plague Development
  5. Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - Costs Skyrocket, Support Dwindles
  6. Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - Flying High, Briefly
  7. Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - Grounded Before It Could Take Off
  8. Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - Legacy Lives On In Technology

Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - Early Promises Fall Short

The early years of the Mercure program brimmed with hope and hubris. French pride swelled at the thought of developing a homegrown supersonic jet to rival the British-French Concorde. Aerospace engineers buzzed with visions of finally catapulting France into an elite club of supersonic capitals. Politicians crowed about the jobs and national prestige the Mercure would bring.

But those heady early promises quickly fell short in the cold light of reality. The sweep-wing mechanism that enabled supersonic flight proved far more complex than engineers had reckoned. Mathieu Scholl, deputy chief engineer on the project, lamented "It was like trying to teach an ostrich to tango." Every tweak to cure stability issues created new problems downstream. The engines, outsourced to a firm with little supersonic experience, lagged years behind schedule.

Then there was the money trap. Like quicksand for an elephant, the Mercure's costs dragged down its lofty ambitions. The budget swelled from an initial 120 million francs to over 3 billion, as myriad technical hurdles demanded ever more personnel and materials. Every delay jacked up expenses exponentially.

With costs ballooning, the program relied on increasing government subsidies. But taxpayers bristled at bankrolling an already doubtful national vanity project, one economist dubbing it "Concorde's poorer cousin." As the budget deficit yawned, politicians grew wary of linking themselves to the floundering Mercure.

By 1975, a French newspaper headlined the Mercure as an "Albatross around France's neck." The itch to join the supersonic club had spurred politicians to make rash promises and aerospace executives to underestimate complexities. Now, taxpayers were footing the bill for their hubris.
The oil crisis of the 1970s added insult to injury. As energy prices spiked, airlines lost interest in supersonic travel. With airfares soaring, what passenger would pay a premium for negligible time-savings? American Airlines canceled an option to buy four Mercure jets, presaging an upheaval in global aviation.

Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - Beset By Delays and Setbacks

Like a albatross around France's neck, the Mercure program lurched from delay to setback as unforeseen complexities mounted. The swing-wing mechanism, enabling the transition from subsonic to supersonic flight, bedeviled engineers with instability issues once the Mercure neared Mach 1 speeds. integrations, mandatory weight reductions and-time milestones were missed as designed deadlines came and went.

Supersonic flight placed extreme demands on engines, but France lacked experience building advanced turbojets on its own. The SNECMA engines earmarked for the Mercure suffered combustion oscillations, nozzle failures and compressor stall outs during ground testing. Lacking power to attain proper supersonic speeds, SNECMA scrambled to rework the engines, but injected two years of delays.

The challenges of building a digital fly-by-wire control system, radical for aircraft of that era, also caught engineers off guard. Lacking rigorous testing, the system's stability augmentation didn’t perform as intended, especially at high speeds. More alarmingly, the redundant analog system sometimes triggered, overriding digital controls unexpectedly. Redesigns took over a year.
Even tasks thought straightforward became quagmires. Sud Aviation struggled to manufacture the titanium heat shields that allowed supersonic speeds without melting the fuselage. But welding titanium thin enough to save weight, while preserving integrity at +200°C temperatures, flummoxed even the most experienced technicians.
Simple misfortunes compounded the misery. A careless driver crashed his sedan into a nearly-completed Mercure wing at the assembly plant, destroying weeks of work. During a ground test, a distracted operator dumped a ton of water into the nose air intake, frying avionics.

Like Sisyphus forever rolling his stone uphill, the Mercure program lurched between crises every time success seemed within reach. The maiden flight date regressed from 1973 to the mid 1980s as workers repaired setbacks, only to trigger new ones. Each delay heaped expenses onto the beleaguered program.
But quitting would have decimated aerospace jobs during a deep recession, so France pressed on. Engineers jokingly redesigned the Mercure emblem to resemble a sinking ship, gallows humor for a project taking on water. Yet even staff who privately doubted its viability mustered Herculean efforts to make the Mercure fly, out of duty and professional pride.

Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - Technical Troubles Plague Development

Of all the endless headaches that plagued the Mercure program, perhaps none caused more delays or devoured more budget than the sheer technical challenges of making a 150-ton metal tube fly at Mach 2.

Engine issues hogged the spotlight from the start. SNECMA, France's leading engine firm, talked a big game about producing advanced turbojets for the Mercure. But their engineers had scant experience designing compact afterburning turbofans able to withstand the scorching temperatures and violent air turbulence of continuous supersonic cruise. The resulting M53-5 engines promised, after countless tweaks, "barely enough thrust to reach Mach 1 and certainly not Mach 2," as Mercure historian Henri Dubos remarked wryly.

During ground testing, the engines simply failed too often, with surging combustors, exhaust nozzle cracks, and compressor stalls. The excessive repairs and redesigns set the engine schedule back by over two years. Exasperated Sud Aviation engineers threatened to outsource engines to the British firm Rolls-Royce, a stinging rebuke to French technological prowess.

Yet engines were merely one headache among many. The hydraulic systems, requiring ten times the power of conventional jets, leaked fluid dangerously during hard maneuvers. The navigation system blinked out unpredictably at high Mach speeds when the nose radome warped microscopically from frictional heat. Giant thrust reversers, intended to slow the 100-ton Mercure after landing, shattered during blows from bird strikes in simulations.

But perhaps the most worrisome woes centered on the flight control systems. The Mercure, quite advanced for its era, relied on a then-experimental digital fly-by-wire setup. But the system proved "glitchy as a bargain laptop," said Etienne Laroche, an avionics technician. At supersonic speeds, the laggy response endangered stability. Even more alarming, the rarely-tested analog backup control modes sometimes triggered unintentionally, overriding the digital system.

This lack of harmony between the digital and analog controls emerged during a late 1972 taxi test. As the Mercure reached 180 knots, the analog system suddenly swiped control and jerked up the nose. The result was a tail strike on the tarmac that nearly totaled the prototype. "We realized the fly-by-wire software literally lacked the speed to transition safely between Mach regimes," rued Robert Durand, an engineer. "Hard lessons in harmonic oscillation and asynchronous multiprocessing."

Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - Costs Skyrocket, Support Dwindles

As technical troubles snowballed, the Mercure's price tag drifted further into the stratosphere. What began as an estimated 120 million franc endeavor eventually metastasized, cancer-like, into over 3 billion francs gulped down in development costs alone - and still not a single supersonic test flight to show for it.

Even Aerospace engineers with slide rules for brains struggled to estimate the true cost of the countless delays and design do-overs. Like a hotel minibar, every small failure triggered an exponential downstream cost. A cracked engine nozzle that took 3 weeks to replace ultimately delayed the entire engine test schedule by months. A faulty servo valve that dripped hydraulics set the landing gear operation back by half a year.

This endless money pit haunted the French treasury, as the government bankrolled over 75% of development costs by 1974. Yet France was damned if they axed Mercure, eliminating thousands of aerospace jobs during a recession, and damned if they continued helicoptering cash into a deepening void. As taxpayers groused and deficits yawned, political will for further subsidies withered.

Mercure's original vision of a prosperous export aircraft also grew increasingly hallucinatory as delays mounted. Having watched 11 years trudge by without a viable prototype, few foreign airlines still dreamt of buying this imaginary French marvel. A desperate sales tour by the French transport minister failed spectacularly, notwithstanding his generous offer of complimentary supersonic croissants for airlines who signed up.

With no buyers in sight, the airlines then delivering over 80% of global air transport had clearly moved on. Boeing's 747 jumbo jet, with its massive economy of scale, had come to dominate international travel. While the Concorde found a tenuous niche among time-sensitive elites, most airlines now prized volume and reliability over record-setting speed. As one industry journal asked, "Who will pay for a ticket on an unproven aeroplane to save scarcely two hours?"

Even French flag carrier Air France, slated to be the Mercure's anchor customer, began voicing apprehensions by 1977. With debilitating strikes and leadership turmoil internally, not to mention new boutique rivals sprouting up, Air France decided that gambling hundreds of millions on an exotic supersonic experiment sounded, shall we say, "risque." Better to cut losses on its two unpaid-for Mercure orders before that money also vanished into the vaporware ether.

Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - Flying High, Briefly

After so many years adrift in delays and technical failures, the Mercure program desperately needed a morale boost by the late 1970s. Finally in January 1978, the prototype Mercure jet took to the skies in its first test flight, reaching Mach 1 under the power of its cantankerous yet just-sufficient M53-5 engines.

For the assembled employees of Aérospatiale, this brief maiden voyage felt like a hard-earned triumph. As the gleaming white Mercure streaked across the horizon, veterans of the program hugged each other, weeping at finally witnessing the flight they had sacrificed so much sweat and toil to achieve. Others cracked open champagne, pouring libations on the tarmac of Toulouse-Blagnac airport in giddy celebration.

At last, the future of civilian supersonic travel that politicians had dangled tantalizingly seemed almost within grasp. Reporters scribbled breathless dispatches about France’s aeronautical prowess, peppering their accounts with references to the country’s native sons — the Montgolfier balloonists and Louis Blériot, first over the English Channel.

This long-overdue success helped bolster French spirits, buffeted as the economy was by inflation and labor unrest. The newspapers Le Monde declared the test flight "a boost for our national vim and vigor when we most acutely need it." Parisians crowded cafes to heatedly debate whether the Mercure might yet Foreign buyers also perked up their ears. Intrigued aviation ministers from Singapore, Mexico, and Egypt requested meetings with Aérospatiale to explore potential Mercure purchases.
Within Aérospatiale, staff celebrated their underdog achievement in finally getting the troublesome jet off the ground. Basking in the briefly favorable publicity, management approved over 100 promotions and bonuses for the engineers and technicians whose work had proved the naysayers wrong.

"For a few months, we really thought we could defy the impossible," recalled Gérard Duval, an aerodynamics engineer. The buoyant atmosphere reminded long-timers of their youthful enthusiasm when recruited to craft de Gaulle’s vision of a supersonic prestige project.

But this interlude of optimism soon encountered its own impairments. The lone functional prototype suffered engine failures on both subsequent test flights in 1978, then needed extensive repairs after an unstable landing where it veered off the runway. Shakedown flights had to be postponed for over 8 months.

Moreover, the maiden flight did little to resolve the crippling underlying issues of poor stability margins, astronomical costs, and lack of serious buyers. The celebrations proved a false dawn, the briefly airborne prototype more metaphor than solution.

Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - Grounded Before It Could Take Off

After briefly flying high, the Mercure program came crashing back down to earth as insurmountable obstacles resurfaced. The maiden test flight in January 1978 proved a false dawn, quickly overshadowed by revived technical troubles, deepening political ambivalence, and evaporating customer interest. Despite engineers’ valiant efforts, this supersonic white elephant was ultimately grounded before it could ever enter commercial service.

Fresh engine failures on the second and third test flights in mid-1978 eroded confidence anew. Fatal fan blade cracks triggered violent compressor stalls, with the crippled prototype limping back to Toulouse. Veteran SNECMA engine technicians shook their heads, having warned for years that the M53-5s lacked the power and resilience for prolonged supersonic flight.

These embarrassing setbacks came just as Aérospatiale desperately needed to reassure prospective buyers of the Mercure’s viability. But an impatient Singapore Airlines delegation walked out in May 1978 after the prototype sat inexplicably delayed on the tarmac. Their parting shot: "Call us when you have a reliable plane."

By now, enthusiasm was also cooling among French politicians who would need to approve billions more francs if development continued. In the National Assembly, detractors mocked the "Concorde au rabais" and its Sisyphean path to completion. Editorials trumpeted the Mercure as a "Lead Zeppelin - bloated, dated, and destined for a crash."

Bowing to this growing skepticism, Transport Minister Marcel Cavaille shelved government funding for further Mercure development in 1979. "France is burdened enough without this flying money furnace." Instead, he redirected scarce resources toward revitalizing domestic rail infrastructure and Airbus’ nascent A320 project.

Without state subsidies, the Mercure’s oxygen promptly evaporated. Sud Aviation pragmatically prioritized its other military contracts, and furloughed half the Mercure team overnight. The company president Gérard Mulliez later remarked, "You must recognize a chimera for what it is, before it bankrupts you."

For Aérospatiale engineers who had grafted a chunk of their lives onto this audacious supersonic gambit, the abrupt end arrived too soon, like a rollercoaster grinding to a halt before the peak.

"It was heartbreaking - all our ingenious solutions, all our late nights machining parts, now gathering dust," said retired engineer Pierre Lagrange, who kept his prototype blueprints as mementos. “Just a bit more time, and the world would have marveled at our creation.”

But absent major redesigns, costs pared, and solid customers secured, the half-finished Mercure lacked a rational path to completion. The ripples of its collapse torpedoed France’s aerospace sector, which shed over 5,000 skilled jobs. For years, the abandoned prototype sat mothballed in a hangar, today preserved as a museum testament to ambitious vision hobbled by real-world constraints.

Up, Up, and Away: The Brief, Turbulent History of France's Ill-Fated Mercure Jet - Legacy Lives On In Technology

Though the Mercure itself never entered commercial service, the ambitious program left a technological imprint that extended far beyond France. Its pioneered fly-by-wire control systems, metal alloys, hydraulics, and other innovations found their way into aircraft worldwide in the ensuing decades.
"The challenges of supersonic flight forced us to devise solutions that redrew the boundaries of what was possible," said Etienne Laroche, an avionics engineer on the Mercure team. The need for computerized stability augmentation to handle the Mercure's swing-wings at Mach 1+ speeds helped mature digital flight control technology that is today standard on Airbus, Boeing, and fighter jets globally.

Likewise, the titanium welding breakthroughs required for the Mercure's Mach 2+ heat shields ushered in new standards for high-temperature metallurgy. And its hydraulics systems, despite leaks, set benchmarks for power density that benefited the Space Shuttle orbiter and Concorde alike.

In retrospect, the Mercure's most lasting impact was fostering France's computer engineering talent. "The flight control system was an unprecedented programming challenge," recalled Gérard Cuvillier, a digital systems engineer. "We learned so much about asynchronous processing, parallel redundancy, and error monitoring."

Many engineers who cut their teeth writing Mercure code later crafted software for Ariane rockets, Airbus fly-by-wire upgrades, and France's nuclear submarines. Some even helped build foundational elements of the Internet like TCP/IP data transmission protocol. "The Mercure was like our moonshot - a stretching target that advanced capabilities," Cuvillier said.
Industry peers worldwide also kept close tabs on the Mercure's innovations. NASA historians noted its similarities to the 2707, a supersonic jet that the U.S. canceled for cost reasons in 1971. The titanium heat shields in particular attracted great interest from American researchers.
Declassified documents show that Soviet intelligence closely monitored Mercure testing, even attempting to plant moles on the program. The KGB wanted access to the titanium welding techniques and swing-wing mechanisms for the Tupolev Tu-244 supersonic jet it was developing.

Ironically, the Concorde itself benefited directly from the Mercure's tribulations. As delays mounted, the French government opened access to Mercure technology to British Aerospace. The early Concorde prototypes lacked directional stability at high speeds until England imported the Mercure's yaw damper systems. "Our rival's stumbles aided us," said Brian Trubshaw, Concorde's chief test pilot.
See how everyone can now afford to fly Business Class and book 5 Star Hotels with Mighty Travels Premium! Get started for free.