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Convair F-102 Delta Dagger — proving that area rules

14 November 2012

Convair F-102 Delta Dagger — proving that area rules

Convair brought the F-102 Delta DAgger, a revolutionary jet powered and missile armed interceptor to the U.S. Air Force (USAF), during the days of the Cold War when superpowers had plans to send heavy bombers on nuclear strike missions. The USAF desired supersonic aircraft armed with bomber killing missiles, at the time, so that the interceptor aircraft could cover large areas of responsibility quickly with their speed and just as quickly shoot down intruding bombers.

Convair’s design was remarkable and is noted by its angularity with its delta wing, triangular vertical stabilizer and four-paned canopy— itself triangular. Armed with missiles and rockets the Delta Dagger was a 1950s machine which was quick and agile. But for a timely coincidence in research by Richard Whitcomb it would also have been a failure.

The early Delta Daggers did not have sufficient power to fly faster than Mach in level flight. The conventional wisdom of speed in that day was to have tubular fuselages and an over all clean design but as transonic speeds were approached wave drag developed, then known only as a phenomena. Wave drag is a type of turbulence and in this case it meant speed and power draining drag.

Richard Whitcomb, though, had been studying wave drag when he experienced an epiphany one day, after much research. He realized that the entire aircraft had to be considered as a whole when considering high subsonic and transonic air flow and this led to one of the 20th Century’s greatest aerodynamic breakthroughs — Area Rule. Essentially this meant to look at the fuselage and wing’s overall cross-sectional area as a whole and relate that value to the theoretical optimum design known as the Sears-Haack body. Where the value is too high then thin it out and when too low then thicken it.

Convair worked with Whitcomb to redesign the F-102 and most notably pinched in the mid fuselage, often called the “Coke Bottle” shape but also thickened the fuselage aft of the wing — in following with the Area Rule concept. The results were nearly miraculous with the Delta Dagger then flying 25% faster with the same power. Yes, a 25% boost in performance! The engineers must have hardly believed their eyes at the performance increase.

The Dagger could be armed with Hughes AIM-4 Falcon missiles, either the heat seeking AIM-4D or the radar homing AIM-4A, were carried internally within twin longitudinal weapon’s bays. The nuclear armed and only nuclear air-to-air guided missile, the Hughes AIM-26, could also be carried. The weapons bay doors were also lethal since up to 24 2.75-inch rockets could be launched from them.

The  USAF had continued production of the F-102 before the new design was thoroughly explored which led to so many improvements of the F-102A model that the F-102B was redesignated the F-106 — see the next post on Friday to read about Convair’s F-106 Delta Dart. The National Museum of the U.S. Air Force has this fact sheet on the F-102.

Nose-on view of the Convair F-102 Delta Dagger at the Castle Air Museum — photo by Joseph May

The F102′s angularity cannot be missed — photo by Joseph May

The Convair F-102 Delta Dagger the National Museum of the U.S. Air Force — photo by Joseph May

The pilots forward view was left a bit wanting but the canopy design shows the emphasis being placed upon speed for the Delta Dagger — photo by Joseph May

Three Hughes Falcon missiles: the AIM-4A radar missile forward and Hughes AIM-4D infra-red (IR) missile aft with the nuclear radar AIM-26 in white, also note the tubes for the 2.75-inch rockets — photo by Joseph May

Pilots of the F-102 flew from a cockpit meant for the business of launching missile against bombers and not for air superiority combat — photo by Joseph May

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