Why was the Convair 990 built?

It was the 1960s, and two of the most dominant jetliners at that time were the Boeing 707 and the Douglas DC-8. They offered more capacity, comfort, longer range, and faster travel times compared to turboprop planes. However, one company aimed to outperform the DC-8 and the 707, with speed as its defining factor. This was the Convair 990 Coronado, a high-speed subsonic aircraft that I will now discuss.

In the 1950s and 1960s, speed was a defining characteristic of air travel. The goal was to transport people more quickly and comfortably to their destinations. Convair sought to capitalize on a market segment desiring faster aircraft. The 880, Convair 990’s older and smaller sibling, couldn’t match the capacity of the DC-8 and Boeing 707. Therefore, Convair developed a longer aircraft with a faster top speed than both the Boeing 707 and the DC-8.

Convair 990A specs

The Convair 990A is a four-engine jet aircraft capable of speeds up to Mach .871. It is powered by four General Electric CJ805-23B turbofan engines, each producing a thrust of 16,050 lbf. This gives the aircraft a range of 6,115 km. It has a capacity of up to 149 passengers and a crew comprising four pilots, in addition to the cabin crew.

Compared to the 880, the 990 was longer by 3 meters. Although it still carried fewer passengers than the Boeing 707 (110 to 189) or the Douglas DC-8 (105 to 173), the 990 boasted a cruising speed that was 25 to 35 mph (40 to 56 km/h) faster than both.

Why was the Convair 990 built in the first place?

American Airlines, seeking to do coast-to-coast trips from New York to Los Angeles against the wind, requested Convair, a division of General Dynamics, to construct an aircraft larger than the 880 but capable of flying at the same speed.

Convair assured American Airlines that they could construct a jet capable of reaching a top speed of 635 mph (1,022 km/h). Convair even offered guarantees that if the Convair 990 did not meet its promised speed, the company would pay millions of dollars in fines to American Airlines.

One significant modification from the 880 was the inclusion of large anti-shock bodies on the upper trailing edge of the wings, which helped raise the critical Mach number by reducing transonic drag. The larger inboard shock bodies also doubled as supplementary fuel tanks. During the design phase, Convair decided to incorporate fuel into the outboard pods as well. However, during initial test flights, this additional weight caused the outboard engines to oscillate under certain conditions. To address this issue, another revision involved shortening the pods by 28 inches (710 mm), which, in turn, increased drag.

Additionally, the engines were upgraded to General Electric CJ-805-23s, which were distinctive in that they used a fan stage at the rear of the engines, as opposed to the Pratt & Whitney JT3D that powered the 990’s rivals. The J79 engine, used in supersonic military aircraft, was adapted for commercial use in the CJ-805 and CJ805-23 and did not employ afterburning fuel. Like most J79 models, these engines were smokey, although secondary operator Spantax eventually had their engines retrofitted with low-smoke combustion chambers in the 1970s.

Not living up to what was expected

Because the 990 did not fulfill its promised performance, American Airlines reduced its order. When the 990A was developed, among other modifications, fairings were added to the engine nacelles. The aircraft was initially promised to make coast-to-coast nonstop flights from JFK to LAX, but it was never able to deliver on this promise, despite the changes made from the original 880 and those implemented in response to drag issues during testing. The flight schedules of American Airlines’ 707 and 990A showed little to no difference in time. By 1967, American Airlines began phasing out its 990As.

In May 1961, one of the pre-production Convair 990 aircraft achieved the fastest true airspeed ever recorded by a commercial jet transport, reaching 675 mph (1,086 kph) at an altitude of 22,000 feet. This record was set during a demonstration of the aircraft’s capabilities, where it dived from 32,000 ft to 22,500 ft, reaching a speed of Mach .97, showcasing the gap between its operating speed and its potential performance.

The end of the 990A

Additionally, the Convair 990A was known for its high fuel consumption. For comparison, a modern Boeing 737 MAX 8, typically carrying 162 passengers, consumes approximately 4,460 lb (2.02 t) of fuel per hour at Mach 0.78 (450 kn; 833 km/h) under less-than-ideal conditions. In contrast, the 990A was reported to burn around 13,750 pounds (6.24 t) of fuel per hour at Mach 0.84 (484 kn; 897 km/h) while flying at 35,000 feet (11 km).

The Boeing 720 and Boeing 720B, which are variants of the Boeing 707, and later the Boeing 727, quickly filled the market niche that the 990 had targeted. By the time the assembly line was shut down in 1963, only 37 Convair 990s had been built, bringing the total number of commercial jet aircraft manufactured by General Dynamics to 102 airframes.