North American’s F-100 Super Sabre served the United States for 25 years. The Hun was the first American fighter jet capable of level supersonic flight. Progenitor of the Century Series, the F-100 was conceived in 1949 and developed during the 1950s- serving during some of the hottest years of the Cold War. North American’s justly famous F-86 Sabre jet fighter was the aircraft upon which the Hun was loosely based. One of the first American aircraft to incorporate significant amounts of titanium in its structure, the F-100 was much more than a redesigned F-86.
The F-100 began as an unsolicited proposal for a supersonic day fighter to the United States Air Force (USAF). Because the F-100 was equipped with wings swept at 45 degrees it was initially dubbed the Sabre 45. North American’s mockup of the design was inspected on July 7th 1951, and after over a hundred modifications, the new aircraft was accepted as the F-100 on November 30th 1951. On January 3rd 1952 the USAF ordered two prototypes (YF-100As) to be followed quickly by 23 F-100As for delivery in February of 1952 and 250 more F-100As for delivery in August of 1952.
First flown in May of 1953, the YF-100A prototype performed so well that the F-100A went into production just five months later. But when Pearl Harbor hero and North American test pilot George Welch was killed in an early production F-100A during October of 1954 the cause was determined to be yaw instability-induced inertia coupling. Additional flight testing revealed that as the F-100A approached stall speeds, lift reduction on the outer wings could cause a violent pitch-up- the Sabre Dance.
Potentially deadly design issues notwithstanding, the F-100A was pressed into service quickly due to delays in the other fighter-bomber in development at the time, Republic’s F-84F Thunderstreak. The Hun went into service with the USAF Tactical Air Command (TAC) in September of 1954. TAC immediately requested that subsequently delivered F-100s be capable of “special weapons” (tactical nuclear weapons) delivery and that they keep the four 20 millimeter cannons mounted in the forward fuselage. However, no less than six major mishaps occurred within just two months. The entire fleet of F-100As was grounded until February of 1955.
One noteworthy modification program was the Slick Chick RF-100A photographic reconnaissance variant. Six F-100As were modified to fit cameras in place of the gun armament. Because the camera equipment would not all fit within the available space the engineers added a bulge that extended from below the windshield almost to the trailing edge of the wing. RF-100As apparently flew some highly sensitive missions over Soviet-occupied territories in Europe during some of the hottest days of the Cold War. Many of these missions are still classified today. After their service in Europe the Slick Chicks were used by the Taiwanese. Those missions are also still classified too.
Haste Makes Waste
The 479th Tactical Fighter Wing (TFW) based at George Air Force Base (AFB) in Victorville, California finally gained operational status during September of 1955. The experience of the 479th with the F-100A served to hasten both the replacement of the F-100A with the F-100C and the 479th to re-equip with Lockheed F-104 Starfighters within just three years. Other F-100As were all withdrawn from service by 1961 after 47 were lost to mishaps, recalled once when The Berlin Crisis took place, and finally retired by 1970 when replaced by other jets.
The F-100C was the fighter-bomber the USAF wanted and not what it needed. The F-100C retained most of the design deficiencies of the F-100A but could drop bombs. Equipped with an uprated Pratt & Whitney J57-P-21 turbojet engine that was as prone to compressor stalls as the previous version, the F-100C was later modified with yaw dampers to reduce instances of inertia coupling. Capable of carrying drop tanks but incapable of carrying all standard USAF ordnance, F-100Cs were phased out of service by 1970 after 85 of them were lost to operational mishaps.
By the time the F-100D variant was introduced in 1956 the Hun had become a ground attack jet- an excellent ground attack jet, but nothing more. Other USAF fighters would take over the role of fighter-interceptor. The F-100D was equipped with extended wings and a larger vertical stabilizer, an autopilot and upgraded avionics. Later production F-100Ds could carry the AIM-9 Sidewinder infrared-guided air-to-air missile and the Martin GAM-83A / AGM-12 Bullpup air-to-surface missile. But not everything was rosy with the F-100D either.
At first the F-100D was plagued by electrical system problems, landing gear and brake parachute malfunctions, and the inflight refueling probes had a tendency to part with the aircraft during high speed maneuvers. Due to inconsistent application of field or depot fixes for these issues it became necessary to review the entire fleet of 700 aircraft to standardize them. This was eventually accomplished via the High Wire standardized modification program. Later the Combat Skyspot program added X band radar to facilitate ground-directed bombing day or night by F-100Ds.
The Crucible: Air War in Vietnam
The Hun served in Southeast Asia longer than any other American jet. They served as MiG combat air patrol (MiGCAP) escorts for F-105 Thunderchiefs and other fighter-bombers, as Misty forward air controllers (FACs), and when modified with radar receiving equipment to employ anti-radar missiles like the AGM-65 Shrike, in the defense suppression or Wild Weasel roles. During a MiGCAP escorting F-105s attacking the Thanh Hoa bridge, F-100s also fought the first air-to-air jet combat of the Vietnam war, shooting down three North Vietnamese MiG-17s- even though they were never officially credited as aerial victories.
Air National Guard F-100 squadrons flew 24,000 sorties and 38,000 combat hours in Southeast Asia. These Guardsmen, many of them from the 120th TFS Cougars of the Colorado ANG, the 136th TFS Rocky’s Raiders of the New York ANG, the 174th TFS Bats of the Iowa ANG, and the 188th TFS Tacos of the New Mexico ANG, were consistently rated as some of the most effective and efficient Air Force assets in-theater. They delivered some 4,000,000 rounds of 20 millimeter ammunition, 15,000 tons of bombs, and 5000 tons of napalm on enemy targets while losing 14 F-100s and seven pilots killed in action.
There were 242 F-100s lost in Southeast Asia, most of them to anti-aircraft fire. They were replaced in-country largely by the Republic F-105 Thunderchief and the McDonnell Douglas F-4 Phantom II. But having flown more than 360,000 sorties the Huns had more than earned their keep. After 1965, as other types took over their roles in missions over North Vietnam F-100s continued flying missions and logging combat hours as close air support (CAS) and ground attack aircraft south of the DMZ. F-100s finally rotated back to the world for good in July of 1971.
Improving the Breed
As the F-100D continued in service and was found to be such a workhorse in Southeast Asia the jets underwent a service life extension program to more than double the design life of the airframe. Wings were fitted with external bracing strips. But F-100 losses in Vietnam once topped 50 aircraft in a single month. Overall Air Force losses totaled more than a dozen several times. Attrition dictated that at one time the current operational pace in Vietnam coupled with other operational losses the USAF would simply run out of F-100Ds. But the F-100D made a sterling name for itself in Southeast Asia nonetheless.
One particularly impressive modification to the F-100D involved attaching an Astrodyne booster rocket, capable of 150,000 pounds of thrust, to the belly of an F-100D. When the rocket booster fired the Hun would be thrown into the air, after which the booster would be jettisoned and the jet free to accomplish its mission under “normal” circumstances. They tried it on June 7th 1957 and it worked, so they built it into later production airframes. This capability was called Zero Length Launch (ZeLL) and was tried with several tactical aircraft during the 1960s.
The USAF Thunderbirds flew F-100C Super Sabres until they were replaced by Republic F-105 Thunderchiefs in 1964. After the Thud proved to be an unacceptable aircraft for the Team they reverted back to Super Sabres, albeit the F-100D. Another Air Force flight demonstration team, the Skyblazers, were formed in 1949 and were based in Europe, flying their F-100s exclusively overseas until just before the Thunderbirds performed in Europe for the first time in 1963. The Thunderbirds transitioned to the McDonnell Douglas F-4E Phantom II in 1969.
Still Improving the Breed
As the F-100s soldiered on they were modified to improve their electronics, structures were strengthened, and ease of maintenance was improved. Wing fences appeared. Their afterburners were replaced with the simpler but more advanced afterburners from retired USAF Convair F-102 Delta Dagger interceptors which had been replaced by Convair’s F-106 Delta Dart. Compressor stall issues were finally (mostly) resolved when the afterburner modifications were made during the 1970s. Maintenance of the Delta Dagger afterburners was simpler as well.
A two-seat trainer version of the F-100, the F-100F, first entered service during 1958. Many of the TAC squadrons received a couple of these trainers, which were modified along with the F-100Ds to improve weapons delivery capabilities and structural integrity. But F-100Fs were subject to similar attrition rates as the F-100D, with 74 of them lost to mishaps by 1970. F-100Fs gained some measure of fame as Commando Sabre fast FAC and Iron Hand / Wild Weasel I aircraft in the skies over Southeast Asia. Of the 2,294 F-100s (all variants) produced by North American between 1953 and 1959 an astounding total of 889 F-100s (all variants) were lost to accidents during the Super Sabre’s service with the USAF- 116 of them during 1958 alone.
F-100s were replaced in front-line USAF service by several newer Air Force types by 1972, among them the Fairchild-Republic A-10 Thunderbolt II and the Vought A-7D Corsair II. Of course McDonnell Douglas F-4 Phantom IIs replaced them as well. But Air National Guard (ANG) units flew them for several more years, sometimes serving as MiG-15, MiG-17, and MiG-19 simulators and as training partners in dissimilar air combat training (DACT) with more advanced fighters. The ANG eventually retired the last F-100s from operational use in 1979. More than 200 of them were converted into QF-100 drones and expended as targets during the development of today’s weapons systems. F-100s were also used as flight test chase aircraft out of Edwards AFB for many years.
In addition to the USAF, The Republic of China (Taiwan), Denmark, France, and Turkey operated Super Sabres. The Royal Danish Air Force and Turkish Air Force were the last F-100 operators, retiring their F-100s in 1982. There are a couple of several F-100F “warbirds” flying under private ownership today. Here is a link to a story we did some time ago featuring Colonel Bud Day and the Collings Foundation F-100F. Enjoy!