Convair 990 Coronado

Design and development

American Airlines asked Convair to design an aircraft for coast-to-coast flights, able to fly nonstop from New York City to Los Angeles against the wind after Boeing had flat out refused. They wanted a larger passenger capacity than the Convair 880 and 880M, which were the smallest of the first-generation U.S. jet airliners. The design was known as the Convair 600 and was redesignated the Convair 990 in the month of its first flight. The 990 began flight testing on January 24, 1961.

One change from the 880 was the large anti-shock bodies on the upper trailing edge of the wings, to increase the critical Mach by reducing transonic drag. The inboard shock bodies, which were larger, were also used for additional fuel tankage. Later during the design period, Convair modified the design to include fuel in the outboard pods as well, but during the initial test flights the extra weight caused the outboard engines to oscillate in certain conditions. The pods were redesigned once more and shortened by 28 inches (710 mm), causing increased drag. The inner set of pods were used to route the fuel-dump tubes from the fuel tanks, terminating in a prominent outlet.

The engines were also changed to the uprated General Electric CJ-805-23s, which were unique in that they used a fan stage at the rear of the engines, compared to the fan stage at the front of the engine found on the Pratt & Whitney JT3D that powered the 990's competitors. The engine was a simplified, non-afterburning civil turbofan version of the J79 turbojet, used in supersonic military aircraft. Like most versions of the J79, the CJ805 and CJ805-23 were smoky, although secondary operator Spantax eventually had their engines refitted with low-smoke combustion chambers in the 1970s.

Like the 880, 990s incorporated a dorsal "raceway" added to the top of the fuselage to house the two ADF antennas and one VHF antenna.

Operational history

The 990 did not meet the specifications promised, and American Airlines reduced its order as a result. The 990A was developed by adding fairings to the engine nacelles, among other changes. Despite the modifications from the basic 880 and those in response to drag problems in testing, the aircraft never lived up to its promise of coast-to-coast nonstop capability from JFK to LAX. American Airlines' timetables show little or no difference in scheduled time between 707 and 990A flights. AA began to dispose of its 990As in 1967.

During May 1961, one of the pre-production 990 aircraft, while demonstrating the margin between its operating speed and its capability during a dive at .97 Mach from 32,000 ft to 22,500 ft, reached 675 miles per hour (587 kn; 1,086 km/h) at an altitude of 22,000 feet (6.7 km): the fastest true airspeed ever attained by a commercial jet transport at that time. However, in level flight the maximum speed, 0.84 M, was less than that guaranteed to American Airlines, 0.89 M, because the drag levels with the anti-shock bodies were much higher than predicted. A drag reduction program was instituted during which streamlining of the engine pylon/wing interface and addition of nacelle fairings achieved 0.89 M.

In 1963, the 990A was reported to burn 13,750 pounds (6.24 t) per hour of fuel at Mach 0.84 (484 kn; 897 km/h; 557 mph) at 35,000 feet (11 km) at a mass of 200,000 pounds (91 t). In contrast, a modern Boeing 737 MAX 8 typically carries 162 passengers and burns 4,460 lb (2.02 t) per hour at Mach 0.78 (450 kn; 833 km/h; 518 mph) at sub-optimal parameters.

Swissair bought eight 990As beginning in 1962, operating them on long-distance routes to South America, West Africa, the Middle and Far East, as well as on European routes with heavy traffic. Their fleet was withdrawn from service in 1975. Scandinavian Airlines (SAS) also operated 990A Coronados on their long-haul schedules to Tokyo and other destinations in the Far East and also to South America and Africa.

The 990's niche was soon captured by the Boeing 720 and Boeing 720B, derivatives of the Boeing 707, and later by the Boeing 727. By the time the assembly line shut down in 1963, only 37 990s had been produced, bringing General Dynamics' entire production of commercial jet airliners to 102 airframes. The failure of airlines to broadly accept the Convair 880 and 990 led Convair's parent company, General Dynamics, to suffer one of the largest corporate losses in history. As a result, Convair exited the jet airliner business, although it later built fuselages for McDonnell Douglas, specifically for the DC-10, KC-10 and MD-11.

When the major airlines retired their Convair 990s, they found a second life on charter airlines. Spantax of Spain had a large fleet until the mid-1980s, as did Denver Ports of Call. In 1967, Alaska Airlines purchased Convair 990 PP-VJE from Varig, and operated it as N987AS in scheduled airline service until 1975.