Continental Air Defense- The Century Series

Probably the most astounding leap in aircraft performance in history was in the 10 years from 1950 to 1960. Aircraft went from propellers to the early jets, to jets capable of more than twice the speed of sound and operations at more than twice the altitude of World War II’s combat aircraft.

The “Century Series” fighters were those jets, starting with the F-100 Super Sabre, that entered service during this decade of rapid development.  Generally, the F-100, the F-101, F-102, F-104, F-105, and F-106 are counted among the series. Some folks credit the F-4 Phantom as the last of the Century Series (its original Air Force designation was F-110 Spectre) and a few heretics count the F-111 Aardvark as the last Century Series. These folks are wrong.

Three members of the Century Series figured prominently in the Air Defense Command’s efforts during the Cold War.

The F-101 Voodoo was initially conceived as a single seat, gun-armed long range escort for Strategic Air Command’s bombers. As SAC soured on the concept of escort fighters, ADC took a look at the fast, long range jet and saw the possibilities. The F-101B was longer, with a deeper body to carry more fuel. It also had a second seat to accommodate a radar operator for its fire control system. Rather than a gun armament, the F-101B had an unusual revolving belly tray. Two AIM-4 Falcon missiles would be carried externally under the belly, one radar guided, one infra-red homing. After those two missiles were fired, the belly tray would revolve 180 degrees, exposing another pair of Falcons, which had been stored internally.  The F-101 served with the USAF from 1959 to 1971 (and  with the Air National Guard until 1982). Additionally, Canada replaced their CF-100 Canucks with former USAF Voodoos, and operated them as the CF-101B. They were replaced in Canadian service by the F/A-18 in the early 1980s. A total of 479 F-101Bs were built.

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The F-101 was something of a stop-gap. It had only been chosen for production mainly because the jet ADC really wanted just wasn’t working.

The plane the ADC really wanted, the F-102 Delta Dagger, was one of the very first programs in which the airframe only a portion of the program. It was an integrated procurement. The program looked to meld together a supersonic, high altitude airframe, a complex fire control system (the Hughes MG-3, which controlled the radar) and a guided missile armament. The airframe of the F-102 was built around a bay for up to six Falcon air-to-air missiles. And for good measure, the weapons bay doors carried up to twenty-four 2.75” Mighty Mouse rockets.

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The F-102 was a very ambitious program, and not surprisingly, several problems cropped up. The MG-3 had a lot of teething problems. The Falcon’s were immature, and further development would be needed before they were a viable weapon. But the biggest problem was that the Air Force’s new supersonic interceptor… wasn’t supersonic. The YF-102 just would not break the speed of sound. The issue turned out to be a concept called area-rule. We’re used to seeing streamlined shapes. Intuitively, we know what looks aerodynamic. And for the most part, our eyes don’t trick us. But in the transition from subsonic to supersonic speeds (the transonic regime), looks can be deceiving.  The original YF-102 design made the fuselage taper from a needle point to its thickest point being around the middle of the fuselage, and tapering again until the jet exhaust. But the designers didn’t account for the fact that the small frontal area of the leading edge of the wings contributed to the overall transonic drag of the jet. It turned out, where the wingspan was greatest, the thickness of the fuselage needed to be narrower.  The total frontal area had to remain relatively constant- hence “area rule.” The fix was to “pinch” the fuselage in the middle, leading to the “coke bottle” form (a more visible version of this is exemplified by the F-105). After a rushed 117 day crash program, a rebuilt YF-102A took to the air and proved its supersonic bona fides. “The Deuce”  was capable of over 800 miles per hour at an altitude of 50,000 feet.

  Eventually, bugs with the fire control system and the Falcon missiles were also worked out. The F-102 came to be the backbone of the ADC, with 875 F-102s built. There was also a two-seat trainer version, the TF-102. It featured side-by-side seating for a pilot and a student in a totally revised nose. Not surprisingly, it wasn’t quite capable of supersonic speeds. It did, however, otherwise retain combat capability.

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The Deuce served not only in the continental air defense mission, but also served overseas, in Europe, Korea, and for several years, in the Vietnam conflict. In the early years of the Vietnam conflict, there was great concern that North Vietnam would attempt a raid on South Vietnamese airfields using its small force of IL-28 Beagle bombers. F-102s were deployed as an alert force to fend off any such raids. As the spectre of Beagle raids faded, F-102s began to serve as escorts for B-52 Arc Light missions, and even to perform trails as a ground attack aircraft. The Mighty Mouse rockets in the weapons bay doors were used in daylight.  At night, the IR guided version of the Falcon could target cooking fires or trucks. It wasn’t particularly successful as  a ground attack plane, but it was at least an innovative attempt. It was this mission in Vietnam that George W. Bush volunteered for. By the time he applied, however, F-102 deployments to Vietnam were ending.  One F-102 was shot down by a MiG-21 while escorting B-52s over Laos in 1968. There were no confirmed MiG kills by F-102s, but postwar North Vietnamese records suggest there may have been as many as three.

Greece and Turkey both operated surplus F-102s, and both flew them in combat during the Cyprus incident in 1974, with two Turkish Deuces allegedly being shot down.

While Convair and the Air Force were somewhat please with the F-102, they always knew they could do better. Almost from Day One of the F-102 program, they had their eye on what was then called the F-102B, the ultimate interceptor. The changes in aerodynamics, fire control electronics, and engine technology meant a far better aircraft was soon to be. The great number of changes lead to an entirely new designation for what was to be the last built-for-purpose interceptor in US service, the F-106 Delta Dart.

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The strong family resemblance to the F-102 is obvious. But the F-106 was a much aerodynamically cleaner (and aesthetically pleasing) design. The J75 engine was far more powerful than the J57 of the Deuce. The “Six” had the same Falcon missile armament as the Deuce, but deleted the rocket armament from the bay doors. The Six also carried the aforementioned AIM-26A Nuclear Falcon, as well as the earlier AIR-2 Genie nuclear rocket. 

The F-106 as fast. Compared to the relatively paltry Mach 1.2 speed of the Deuce, the Six could easily top Mach 2.  Its Hughes MA-1 Fire Control System was optimized to work in the Semi-Automatic Ground Environment (SAGE). The SAGE could actually deliver steering commands directly to the F-106 autopilot, reducing pilot workload and allowing the pilot to concentrate on his radar and weapon systems during the intercept.

Due to the diminishing Soviet bomber threat, and the large numbers of F-102s already in service, only 277 F-106As and 63 two-seat F-106Bs were built.

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Entering service in 1959, the Six served as a sentinel for North American skies well into the late 1980s with the US Air Force and Air National Guard.

As the Century Series left service with the ADC, their places were taken first by F-4 Phantoms, and later by F-15 Eagles and F-16 Fighting Falcons. Eventually,the Air Defense Command’s mission was overtaken by history and its role was taken over by units from the Tactical Air Command (now Air Combat Command) tasked to support NORAD, and by units of the Air National Guard similarly tasked.  Until September 11, 2001, missions by these units were limited to investigating airliners that entered US airspace without properly identifying themselves. In the immediate aftermath of that horrific day, fighters under Operation Noble Eagle provided round-the-clock Combat Air Patrols over several US cities. While the constant patrols are no more, the Air Force still provides a rapid response capability to intercept aircraft in our airspace.

10 thoughts on “Continental Air Defense- The Century Series”

  1. I am under the impression that the USAF originally wanted F110s purely as an interceptor (hence the original grey paint). If so, I am curious as to your disagreement with inclusion as century-series?
    Overall, nice post.

    1. The F-110 (aka F-4 Phantom) was bought and operated by TAC, vice ADC. TAC wanted the jet as a tactical nuclear delivery platform. It’s AJB-3 bombing system wasn’t much for conventional weapons, but was just dandy for an over the shoulder nuke delivery. As a secondary role, it assumed most of the air superiority mission.

      As to not being a Century Series, while numerically it would be included, the heart of the “real” Century Series was the a push by the Air Force over about a 5 year period that led to the development of the family to fulfill specific roles and missions. While it wasn’t an “integrated” procurement program, it was a concurrent program.

      The F-110, by contrast, was forced on the Air Force by McNamara, and its success may have been a factor in his later insistence on the TFX program.

    2. I think Esli is right here. The initial USAF requirement was cast in light of shortfalls in F-106 performance. Only after the first evaluations were those requirements modified to include “bomb carrier” options.

  2. I would also like to point out that there was a purpose-built interceptor in US service until 2006: the F-14 Tomcat.

    1. The Tomcat was an air superiority fighter optimized for the fleet air defense mission. That’s a cat of a different color than a pure interceptor.

      While it was actually a pretty fair dogfighter, the F-106 crews weren’t expected to go over the enemy’s territory and wrest control of the skies from them. It was a purely defensive aircraft.

    2. Nope. Interceptor that turned out to be a decent air superiority fighter. The original mission – and the whole point of AIM-54 was to intercept bombers and ASCMs. It’s a classic interceptor mission.

    3. I’m well aware of the evolution of the program from the F6D Missileer concept, through the TFX/F-111B debacle to the Mighty Tomcat. But there ARE differences between the pure interceptor role of the F-106 and the fleet air defense role of the F-14.

      For one thing, the F-14 wasn’t optimized to work in the SAGE environment (though it was optimized to work with the E-2C). Further, unlike interceptors, the F-14 was also built with lengthy Combat Air Patrols built in mind. Further, it’s flexibility in its weapons loadout (Phx, Sparrow, Sidewinder, gun) was a result of the need for it to also serve as the escort/air superiority fighter for the carrier air wing.

      By the way, I’m not arguing that it couldn’t do the interceptor mission. It could. So could the F-4 (though most AF F-4s in the ADC role weren’t “SAGE’d up” either). Just that they weren’t purpose built for the ADC’s mission.

    4. Well, part of the reason that the Tomcat wasn’t designed to work as part of SAGE is … well, the “G” part, I suspect. It was designed to work with an integrated fleet air defense system, of which the E2 was part, yes. It was, in fact, the outermost segment of a fleet air defense zone. (I’m still curious as to why you’re distinguishing the roles of “fleet air defense” from SAGE in anything more than name and interoperability, when they’re both defending against long-range massed raids of Badgers / Backfires / Bears (oh my!). The roles are really different only in the area and type of asset to be defended.)

      An interceptor in a Naval environment has a different set of requirements than it does on land. Endurance is much more of an important factor. A land base with (effectively) unlimited space can keep a LOT of low endurance aircraft on hand. A carrier, not so much. Response time is also a key: sea-based detection time is at a bit of a premium, even today, and this was even more the case when the Tomcat was designed.

      In order to maximize the coverage – and response time – that you can get out of 2 squadrons, you have to operate with your interception assets airborne, and to do this you need a long loiter time.

      I suppose it could be argued that the inclusion of the gun, rather than a missile-only armament makes it impossible to be an interceptor, though – that shows a desire to get up close and personal …

      Hm.

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