The Bizarre Design Flaw That Ruined The Convair 990

[00:00:06][music] >> General Dynamics executives signed a contract with American Airlines in 1958 [music] promising a new commercial jet that would cruise at 635 mph making it the undisputed king of subsonic travel.

[00:00:20]It was a bold guarantee that meant their newly proposed aircraft, the Convair 990 Coronado, [music] would fly coast-to-coast nearly 45 minutes faster than the Boeing 707 and the Douglas DC-8.

[00:00:32]In their desperate bid to capture a market already dominated by the massive factories in Seattle and Long Beach, Convair executives wagered their entire commercial aviation division on raw, unadulterated speed.

[00:00:45]What they actually built was an aerodynamic riddle that required radical, bizarre structural additions just [music] to meet its contractual obligations, ultimately triggering the largest single corporate financial loss in American history up to that point.

[00:01:00]The aircraft was an undeniable engineering marvel that fundamentally misunderstood the economics of the very jet age it attempted to lead.

[00:01:08]By prioritizing a few extra knots of airspeed over structural simplicity and fuel efficiency, the designers doomed their creation before the first metal was even cut.

[00:01:19]To understand why a major aerospace manufacturer pursued this extreme and uncompromising design philosophy, one must look at the competitive landscape of the late 1950s.

[00:01:30]Boeing had already stunned the world with their swept wing prototypes, which rapidly evolved into the production Boeing 707, while Douglas was securing massive international orders for its competing Douglas DC-8.

[00:01:43]Both of these aircraft were large, highly capable machines designed around the economic reality of carrying well over 100 passengers across oceans and continents with predictable reliability.

[00:01:55]Convair, which operated as a division of General Dynamics, and was previously famous for building the massive B-36 Peacemaker nuclear bomber, realized they were incredibly late to the commercial jet airliner party.

[00:02:07]Instead of trying to build a direct similar-sized competitor to the established giants, they decided to carve out a highly specialized niche for airlines that wanted a premium, ultra-fast, medium-range jetliner.

[00:02:20]This initial strategy resulted in the Convair 880, a sleek, remarkably narrow aircraft designed for five-abreast seating and blistering acceleration. But the major airlines largely ignored it because its carrying capacity was simply too small to be highly profitable on heavily trafficked routes.

[00:02:40]American Airlines, led by their notoriously demanding president C.R.

[00:02:43]Smith, recognized the potential of the Convair design, but refused to buy the aircraft in its original, smaller configuration.

[00:02:51]Smith was looking for an aircraft that could operate out of shorter runways like New York LaGuardia, while still offering transcontinental range and an unmatched speed advantage that he could plaster across marketing billboards nationwide.

[00:03:05]He approached the executives at Convair and essentially demanded a stretched, heavier, and significantly faster version of the earlier jet.

[00:03:13]He wanted a flagship airliner that could guarantee a cruising speed of Mach 0.91, a number that terrified aerodynamicists, but thrilled airline marketing departments.

[00:03:24]Convair eagerly accepted the challenge, >> [music] >> hastily sketching out the dimensions for what would become the Convair 990, >> [music] >> an aircraft that promised to outrun everything in the commercial sky.

[00:03:35]However, pushing a large passenger fuselage with heavy swept wings to the very edge of the sound barrier introduces a host of violent aerodynamic penalties that standard aircraft designs simply cannot handle without burning catastrophic amounts of aviation fuel.

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[00:04:01]The core engineering problem the Convair design team faced was transonic wave drag, a deeply complex fluid dynamics phenomenon that occurs when an aircraft flies close to the speed of sound.

[00:04:13]Even if the aircraft itself is flying at a subsonic speed, like Mach 0.85, the air flowing over the curved top surface of the wing accelerates dramatically, often breaking the sound barrier locally >> [music] >> and reaching supersonic velocities.

[00:04:27]When this localized supersonic airflow eventually slows back down to match the surrounding air, it creates a violent shock wave that separates the smooth boundary layer of air from the wing surface, producing immense aerodynamic drag and violently buffeting the airframe. Boeing and Douglas engineers had prudently settled for cruising speeds around Mach 0.80 to Mach 0.84, balancing acceptable block times with reasonable thrust requirements to keep fuel consumption low.

[00:04:57]Convair did not have that luxury because their entire corporate survival and their ironclad contract with American Airlines relied entirely on achieving that guaranteed Mach 0.91 cruise speed.

[00:05:10]To solve this monumental drag problem without changing the fundamental shape of the wings, the engineers had to apply a relatively new aerodynamic concept called the area rule, which had recently been discovered by an aerodynamicist named Richard Whitcomb.

[00:05:25]The area rule dictated that an aircraft's total cross-sectional area must change smoothly and gradually from the nose to the tail to minimize wave drag at high transonic speeds.

[00:05:37]Applying this rule to a sleek fighter jet with a pinched waist is straightforward, but applying it to a commercial jetliner with a massive continuous cylindrical fuselage and heavy swept wings is exceptionally difficult as the junction where the thick wing root meets the passenger cabin creates a sudden massive spike in the aircraft's cross-sectional area.

[00:05:57]To smooth out this aerodynamic bottleneck and satisfy the area rule, Convair engineers were forced to add four massive teardrop-shaped pods to the trailing edges of the upper wings.

[00:06:08]These prominent, highly unusual structures were officially designated as anti-shock bodies, but they were universally nicknamed Kuchemann carrots by the aviation community, named after the aerodynamicist who mathematically theorized their optimal shape.

[00:06:24]Looking like large inverted canoes resting awkwardly on the back of the wing, their primary aerodynamic purpose was to delay the onset of the shock wave and manipulate the pressure distribution, effectively tricking the supersonic air into flowing smoothly over the wing root without separating.

[00:06:41]As a brilliant secondary engineering bonus, these large hollow pods were utilized as auxiliary fuel tanks, helping to slightly offset the aircraft's notoriously high fuel burn by carrying thousands of extra pounds of kerosene.

[00:06:54]However, they gave the Convair 990 an incredibly bizarre, unmistakable silhouette that puzzled boarding passengers and drew intense scrutiny from rival engineers who wondered if the aerodynamic band-aid was worth the structural complexity.

[00:07:09]Achieving that blistering speed required more than just clever wing aerodynamics and anti-shock bodies. It required raw, unrelenting thrust that standard commercial engines of the era simply could not provide.

[00:07:23]Convair partnered closely with General Electric, selecting the CJ805-23 turbofan engine, which was a heavily modified civilian derivative of the legendary J79 turbojet that powered the supersonic F-4 Phantom military fighter.

[00:07:39]But unlike the engines on competing airliners, which were early forward fan designs where the large bypass fan sits at the front of the engine, General Electric took a highly unconventional and ultimately flawed approach by designing an aft fan engine.

[00:07:54]Instead of putting the large bypass fan at the front intake of the engine compressor, the engineers literally bolted a completely independent free-spinning turbine and fan assembly to the extreme rear exhaust section of the existing turbojet core.

[00:08:09]The scorching hot exhaust gases exiting the core engine forcefully spun this rear turbine, which in turn spun the outer fan blades that drew in cooler bypass air around the outside of the engine casing.

[00:08:21]This complex mechanical arrangement successfully increased total thrust and supposedly improved fuel efficiency over a pure un-bypassed turbojet, giving the aircraft the sheer power it needed to power through the transonic drag rise.

[00:08:36]While this aft fan arrangement provided the massive thrust needed to push the heavy airframe to its guaranteed speeds, it introduced severe operational and environmental drawbacks that plagued the aircraft throughout its agonizingly short life.

[00:08:49]First, the aft fan design was incredibly punishingly loud, producing a distinct high-pitched tearing sound on takeoff that violently rattled airport terminal windows >> [music] >> and generated countless noise complaints from residential neighborhoods surrounding major airports.

[00:09:06]Second, because the heavy fan assembly was located at the extreme rear of the engine nacelle, the engine itself was exceptionally long, back-heavy, and mechanically convoluted, making routine maintenance access a daily nightmare for ground crews who were already struggling to adapt to the complexities of the new jet age.

[00:09:25]Furthermore, despite the theoretical fuel efficiency of adding a bypass fan, the General Electric aft fan engines burned jet fuel at a genuinely alarming rate and produced thick dark trails of unburned carbon exhaust smoke that made the aircraft look like it was suffering an engine fire during every high-power departure.

[00:09:44]The legacy airline soon realized that the minor increase in cruising thrust was absolutely not worth the staggering monthly fuel bills and the constant labor-intensive maintenance headaches associated with the unique aft fan architecture.

[00:09:58]The theoretical brilliance of the anti-shock bodies and the aggressive aft fan engines collided violently with reality when the first production took to the skies in early 1961 for its initial highly anticipated flight test campaign.

[00:10:13]General Dynamics executives were banking heavily on a smooth, rapid certification process.

[00:10:19]But the test pilots quickly discovered that the aircraft was failing to meet its strict speed guarantees and was suffering from dangerous aerodynamic flutter at high speeds.

[00:10:30]The airflow separation between the inboard engine pylons and the lower fuselage was far worse than the scaled wind tunnel models had predicted, creating excessive turbulent drag that physically held the aircraft back from its Mach 0.91 target regardless of how much thrust was applied. Complete panic set in at the highest executive levels of the corporation as American Airlines retained the legal right to completely cancel their massive multi-million dollar fleet order if the strict performance guarantees were not met. A disastrous move that would instantly bankrupt the entire commercial division of Convair.

[00:11:06]A frantic, highly expensive redesign program was immediately launched, forcing legions of engineers to work tirelessly around the clock to reshape the heavy engine pylons, extend the wing leading edges, and subtly modify the shape of the anti-shock bodies to desperately regain the lost aerodynamic performance. This desperate redesign effort dragged on for agonizing months, costing General Dynamics millions of dollars in unbudgeted engineering overtime, and extended flight test expenses while simultaneously destroying their delivery schedule.

[00:11:39]The engineers eventually solved the worst of the drag problems by implementing a series of complex aerodynamic tweaks, including adding Krueger flaps to the leading edge of the wing to improve low-speed lift without sacrificing high-speed airflow, and significantly reshaping the aerodynamic interface where the engine pylons met the underside of the swept wing.

[00:11:59]When the dust finally settled and the test pilot signed off, the heavily modified aircraft, now officially designated the Convair 990A, finally achieved its promised cruising speed.

[00:12:09]But, the damage to the program's industry reputation and financial viability had already been irreversibly done.

[00:12:17]By the time the heavily revised aircraft was ready for actual airline service in 1962, it was significantly overweight compared to original projections, far more expensive to produce than originally estimated, and fatally late to a commercial market [music] that was rapidly shifting its financial priorities. The airlines were no longer interested in paying a massive operational premium for a few extra knots of airspeed. Their boardroom accountants were suddenly hyper-focused on reducing their daily operating costs and maximizing the profit margin of every available seat.

[00:12:51]The fatal blow to the Convair 990 program [music] did not come from a failure of its own internal engineering, but rather from a quiet, devastating revolution happening at the Pratt & Whitney engine factories, who had just introduced the revolutionary JT3D forward fan turbofan engine. Boeing and Douglas immediately recognized the potential of this new power plant and rapidly adopted this highly efficient forward fan engine, bolting it onto their existing, proven airframes to create the much improved Boeing 720B and the Douglas DC-8 Series 50.

[00:13:25]These upgraded competitors absolutely could not match the blistering top speed of the Convair design, but they offered a massive leap in overall fuel efficiency, a vastly greater maximum range, and a much quieter, more pleasant passenger experience. Airline route planners and financial economists quickly ran the operational numbers and realized that the slight speed advantage of the Convair design was entirely negated by the staggering fuel consumption of its thirsty General Electric aft fan engines.

[00:13:54]In a commercial world where rising aviation fuel prices were becoming a dominant factor in airline profitability, buying a thirsty airliner solely for its marketing speed was suddenly viewed by airline boards as borderline corporate malpractice.

[00:14:10]Knowing what you now know about its high operating costs, narrow cabin, and structural compromises, do you think the high-speed design approach was worth it for the airlines? Share your thoughts below. When the aircraft finally entered scheduled daily service with launch customers like American Airlines and Swissair, the harsh operational realities of the commercial airspace system quickly dismantled its primary marketing selling point. The aircraft was undeniably fast, easily overtaking standard Boeing 707s at cruising altitude, but the rigid, congested structure of air traffic control meant that this impressive speed rarely translated into meaningful block time savings for the paying passengers. A flight crew might push the throttles forward and burn an extra 2,000 lb of jet fuel to arrive at the destination 20 minutes early, only to be immediately placed in a low-altitude holding pattern by air traffic controllers who were simply sequencing them behind slower, earlier arriving aircraft.

[00:15:10]The airlines were essentially paying a massive recurring fuel penalty to hurry up and wait, burning away their narrow profit margins in endless circles over crowded terminal airspaces like Chicago O'Hare and New York Kennedy.

[00:15:24]The speed advantage only truly mattered on long unrestricted oceanic routes where air traffic control was minimal, but the aircraft lacked the maximum fuel capacity and range to fly non-stop from Central Europe to the United States West Coast with a full payload, severely limiting its utility for major international flag carriers.

[00:15:44]Inside the passenger cabin, the paying customer experience was heavily compromised by the aggressive speed-focused aerodynamic choices made by the engineering team years prior.

[00:15:55]To minimize frontal aerodynamic drag, the main fuselage of the Convair was noticeably narrower than that of the competing Boeing and Douglas jets.

[00:16:04]But in order to remain economically competitive on a cost per seat basis, airlines demanded a dense six-abreast seating layout.

[00:16:13]This corporate requirement resulted in an exceptionally cramped cabin environment featuring noticeably narrower seats and a tighter center aisle that made boarding, disembarking, and in-flight beverage service a deeply frustrating experience for both passengers and the flight attendants working the route.

[00:16:30]Furthermore, [music] the acoustic noise from the aft fan engines was remarkably intrusive in the rear sections of the cabin, creating a constant high-frequency drone that penetrated the thin aluminum skin and standard acoustic insulation, leaving aft-seated passengers fatigued after long flights.

[00:16:48]While the aircraft offered uniquely large, beautifully designed passenger windows that provided stunning, expansive views of the earth below, the overall interior comfort level was undeniably inferior to the wider, noticeably quieter cabins offered by its direct market competitors.

[00:17:06]Down on the concrete tarmac, the daily operational logistics of handling the aircraft created relentless headaches for airline station managers and contracted maintenance crews who had to turn the aircraft around quickly to maintain the flight schedule.

[00:17:21]Because the aircraft sat unusually low to the ground due to its exceptionally short landing gear struts, ramp workers had to crouch and bend uncomfortably to manually access the lower cargo holds, significantly slowing down the baggage loading process and increasing turnaround times at the gate.

[00:17:37]This low ground clearance also meant that the inboard engine nacelles hung terrifyingly close to the runway surface, drastically increasing the risk of ingesting foreign object debris like rocks or stray hardware during taxiing.

[00:17:51]This required pilots to be exceptionally careful >> [music] >> and highly skilled during crosswind landings to avoid catastrophically scraping an engine pod on the concrete runway when banking into the wind.

[00:18:02]Mechanics universally dreaded the scheduled maintenance checks on the General Electric power plants, as the unique aft fan configuration required highly specialized heavy tooling and complex access procedures that were completely different from the standard Pratt & Whitney engines that powered the rest of their corporate fleet.

[00:18:21]Every additional minute spent wrestling with a stubborn, poorly designed engine cowl, or waiting for a specialized back-ordered parts delivery, eroded the aircraft's daily utilization rate, making it exponentially harder for the airline to recoup their enormous initial capital investment in the airframe.

[00:18:38]>> [music] >> Despite all the terrifying financial metrics and daily operational nightmares, it caused the airline executives and maintenance chiefs. The actual flight crews who commanded the Convair 990 absolutely adored the machine. Veteran pilots frequently described the aircraft as flying exactly like a heavy, overpowered fighter jet, praising its crisp, immediate control responses, exceptional acceleration off the runway, and unshakable aerodynamic stability [music] at high transonic speeds.

[00:19:08]The flight deck was a beautiful analog marvel of the early 1960s, packed from floor to ceiling with a dazzling array of round dials, engine pressure ratio gauges, and complex fuel management panels that required the constant undivided attention of a highly skilled professional flight engineer.

[00:19:27]When cleared by air traffic control to climb without standard airspeed restrictions, the aircraft could easily outclimb virtually any commercial passenger aircraft in the sky, frequently leaving sector controllers genuinely stunned by its sheer vertical performance parameters. For the pilot sitting at the controls, the sheer tactile joy of commanding such a powerful, highly specialized machine far outweighed the grim economic realities discussed in the corporate boardrooms, creating a passionate cult following among aviators that firmly persists in historical aviation circles to this very day.

[00:20:01]Ultimately, the legacy airlines voted with their checkbooks, and the financial results were catastrophically grim for the proud Convair division. American Airlines quickly realized their strategic mistake regarding the speed premium, and began quietly phasing out their fleet after just a few short years of service, aggressively replacing them with the much more practical, highly economical, and easier to maintain Boeing aircraft.

[00:20:26]Production of the Convair 990 permanently ceased after only 37 total airframes were fully assembled and delivered, falling desperately short of the critical break-even point, and leaving General Dynamics holding an ocean of unsold manufacturing parts and unpaid development bills.

[00:20:45]The combined spectacular failure of both the smaller 880 and the larger 990 programs resulted in a total corporate financial write-off of nearly 425 million dollars.

[00:20:57]Adjusted for inflation, this remains one of the most devastating and profound financial blunders in American corporate manufacturing history.

[00:21:06]The massive, unrecoverable losses forced General Dynamics to permanently exit the commercial airliner market entirely, abandoning the highly lucrative field to Boeing, Douglas, [music] and a rising multinational consortium in Europe that would eventually become the Airbus powerhouse.

[00:21:23]Ironically, the exact same characteristics that made the aircraft an economic failure for legacy passenger airlines operating on strict schedules made it highly attractive for specialized operators on the secondary aircraft market.

[00:21:37]Throughout the 1970s, expanding European charter airlines like Spantax and Modern Air purchased the heavily depreciated airframes for a tiny fraction of their original manufacturing cost using their high passenger density capability to pack in budget vacationers for flights from northern Europe down to the sunny Mediterranean coast.

[00:21:58]Without the immense financial pressure to maintain strict, high-frequency corporate schedules for demanding business travelers, the terrifyingly high fuel burn was economically offset by the incredibly cheap acquisition costs of the used airframes.

[00:22:12]This financial dynamic allowed the aircraft to soldier on successfully for another two decades in the package holiday market, flying tourists who cared absolutely nothing about the area rule or transonic drag penalties.

[00:22:24]Meanwhile, the National Aeronautics and Space Administration recognized the incredibly unique performance capabilities of the airframe and purchased several units for use as high-speed, high-altitude airborne research platforms.

[00:22:38]The immense structural strength, high speed, and heavy payload capacity of the aircraft made it absolutely perfect for testing experimental landing gear tire systems for the upcoming Space Shuttle program, as the aircraft could safely replicate the extreme landing speeds required by the space plane.

[00:22:55]NASA also utilized the aircraft extensively for complex atmospheric research missions, where its high subsonic cruise speed and stable high altitude performance were actual tangible scientific advantages, rather than just marketing gimmicks.

[00:23:11]The Convair 990 Coronado stands today as a fascinating, beautiful monument to a very specific moment in aviation history, when raw aerodynamic performance briefly overshadowed cold economic reality. It was an aircraft designed entirely around a single uncompromising metric of maximum speed, built by a proud company that completely failed to realize the commercial aviation industry had already collectively decided that operating efficiency was the true sustainable path to profitability. The bizarre anti-shock body sitting on its wings and the roaring aft fan engines bolted to its low-slung pylons remain brilliant, if entirely misguided, engineering solutions to a complex aerodynamic problem that the airlines ultimately did not want solved at such a massive financial cost.

[00:24:02]While it failed spectacularly as a viable business venture and nearly destroyed its parent company, >> [music] >> it aggressively pushed the boundaries of transonic aerodynamics, and proved definitively that a large passenger airliner could safely and routinely operate at the very turbulent edge of the sound barrier.

[00:24:21]It remains a striking, beautiful reminder that in the unforgiving, penny-pinching world of commercial aviation, building the fastest aircraft in the sky means absolutely nothing if the airlines cannot afford to put fuel in its tanks.

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[00:24:41]Thanks for watching.