The F-100D (company design numbers NA-223, -224, -235, and -245) was an improved version of the F-100C fighter-bomber. It was also the most widely-produced version of the Super Sabre, some 1274 examples being built.
The F-100D was intended as a dedicated fighter-bomber, with no concession being made to a secondary air-superiority role. The F-100D had a wing with an increased root chord, increasing the total wing area to 400.18 square feet. Unlike earlier Super Sabres, the F-100D was equipped with landing flaps, with the added flap area giving rise to the crank-wing trailing edge, which was the familiar distinguishing feature of the F-100D. The F-100D had the same six underwing hard points as the F-100C, but the detachable underwing pylons used forced ejection rather than gravity release for dropping their stores. The vertical fin and rudder were increased in area, and the fin trailing edge featured a larger and wider square protrusion which carried an AN/APR-26(v) rearward radar warning antenna in addition to the usual fuel jettison pipe. The nose-mounted AN/APR-25(v) gun tracking radar of the earlier F-100s was retained. The F-100D was equipped with a Minneapolis-Honeywell MB-3 automatic pilot which allowed the pilot to concentrate on navigation or tactics while the F-100D flew itself to the target. Improved electronic LABS equipment was fitted so that a MK-7, MK-38, or MK-43 nuclear bomb could be delivered. Conventional bomb loads could include six 750-pound or four 1000-pound bombs.
The first F-100D (54-2121) flew on January 24, 1956, piloted by Dan Darnell. Deliveries to the USAF began in September of 1956, the first recipient being the 405th Fighter Bomber Wing at Langley AFB in Virginia. It rapidly replaced the F-100C in most USAF wings. By the end of 1956, 79 F-100Ds were in TAC's operational inventory and 136 F-100Ds were in service at overseas bases in Japan, France, and Morocco.
There were several major deficiencies identified during early service of the F-100D. The F-100D, like the A and C before it, continued to be plagued with bugs. Among these were the unreliability of the electrical system, the incomplete tie-in between the autopilot and the low-altitude bombing system, and the inaccuracy of the MA-3 fire control system. Despite these problems, large numbers of F-100Ds entered the operational inventory before they could be corrected.
Provision for the installation of a quartet of GAR-8 (later designated AIM-9B) Sidewinder air-to-air infrared homing missiles was introduced on the production line with the 184th F-100D. Air-to-air missile armament had initially been tested on six modified F-100Cs.
Also introduced with the 184th F-100D was a provision for centerline-mounted fuselage attachment points. These points could carry "special stores"-a euphemistic term for nuclear weapons.
Nuclear weapons could be carried on the left wing intermediate attachment point or on the fuselage centerline attachment points. The nuclear weapons that could be carried included the Mk 7, Mk 28 EX, Mk 28 RE, Mk 43, TX-43, and TX-43 X1, with yields ranging from a kiloton to nearly ten megatons. For delivery of these nuclear weapons, the F-100D carried the AN/AJB-1B low-altitude bombing system (LABS). This system was used in conjunction with information provided by the A-4 gyro sight to calculate aiming and release information for the toss-bombing of nuclear weapons. In a typical mission, the F-100D would approach the target down on the deck at about 500 mph and pull up at a steady 4Gs acceleration. Partway into what would be a half loop, the bomb would be automatically released by the computer. The plane would then complete the half-loop and undergo a half-roll and head away from the target. The F-100D would then go to full afterburner in order to get as far away as possible from the bomb when it exploded.
In late 1959, 65 F-100Ds were modified to carry the Martin GAM-83A Bullpup air-to-surface missile. The Bullpup missile was optically-guided to its target by the pilot using a radio command joystick to impart guidance commands to the missile while keeping a flare on the missile's tail lined up with the target as seen through his gunsight. The GAM-83A differed from earlier Bullpup versions in that it had an improved radio guidance system that freed the operator from the need to align the target with his sight, permitting guidance from an offset position. Delays in Bullpup deliveries caused the operational debut of the first GAM-83A-equipped F-100D squadron to slip to December of 1960. Unfortunately, this missile was to prove almost useless in Vietnam and was withdrawn from action after only a few sorties.
North American's Columbus, Ohio factory was designated as a second source for the F-100D. The first Columbus-built F-100D (company designation NA-224) with serial number 55-2734 flew on June 12, 1956.
The correction of the F-100D's autopilot problems took longer than expected. The installation of the improved autopilot, originally planned for the 184th F-100D, was delayed to the 384th. In-service F-100Ds were subsequently retrofitted with the improved autopilot.
The last 48 F-100Ds had built-in zero-length launch (ZEL) capability.
The last F-100D rolled off the production lines at Inglewood in August of 1959. Production of the F-100D at Columbus had ended in December of 1957.
Problems were encountered with the engine bearings and with the aircraft's afterburner fuel system. Problems were also encountered with inadvertent bomb releases from the underwing pylons as a result of improper bomb-loading procedures. Mid-air refuelling probes tend to fall off the wing during high-G maneuvers. This problem got so bad that for a period most refueling probes were actually taken off the F-100D aircraft, pending reinforcement of the underwing structure.
By the early 'sixties, the F-100D had been subjected to so many in-service modifications to correct its obvious deficiencies that no two F-100Ds were alike, making for a maintenance and spare parts nightmare. Beginning in 1962, about 700 F-100Ds and Fs were subjected to a series of modifications under *Project High Wire*, a major standardization and upgrading program. The goal of this program was to extend the variety of non-nuclear weapons that could be carried, to eliminate excess weight, and to standardize the cockpit and rewire it completely. Perhaps the most readily noticeable modification produced by the *High Wire* program was the addition of a spring-steel tailhook underneath the rear fuselage. This tailhook was NOT meant for carrier-based operations, but was intended to engage wires at the end of runways to prevent overshooting during bad landings. Aircraft so modified were distinguished by adding one to their production block numbers--for example, the F-100D-25-NA became F-100D-26-NA after modification. These modifications were completed in 1965.
Even after *Project High Wire* was completed, some problems persisted. Malfunctions of the landing gear and the unreliability of the drag chutes accounted for a number of accidents. Compressor stalls of the J57-P-21 engine still occurred with high regularity. A solution to the compressor stall problems eventually was obtained by installing F-102-type afterburners on the F-100D.
The F-100D was widely used in Vietnam. Several F-100 aircraft initially stationed in the Philippines were deployed to Thailand in May of 1962 to try and restrain the Pathet Lao which were busily overrunning most of northwestern Laos. F-100s began to be stationed in South Vietnam beginning in February of 1964. The first combat strike by the F-100D was flown on June 9, 1964 when eight F-100Ds of the 615th Tactical Fighter Squadron flew strikes against targets in the Plaines des Jarres in Laos. The first recorded combat loss was an F-100D (56-3085), shot down on August 18, 1964 over Laos.
Following the Gulf of Tonkin incident, USAF F-100Ds began to fly missions over North Vietnam. These missions were generally of two types--MiG-CAP patrols to protect strike aircraft from attack by marauding North Vietnamese fighters and fighter-bomber strikes carried out with iron bombs against ground targets. On April 1, 1965, F-100Ds flew MiG combat air patrol for a strike force of F-105s that were hitting the Thanh Hoa Bridge in North Vietnam.
During these strikes, the MiGs would try to sneak up on these packages from the rear, make just one firing pass, and then flee. It was assumed that the F-100D would probably not be an effective fighter in air-to-air combat, since it lacked a powerful radar set and could not carry advanced air-to-air weapons. However, every time the MiGs tried to interfere with these strikes they immediately fled as soon as the F-100s turned toward them. Encounters between F-100s and MiGs were very few and far between, and I think that the F-100 fired its guns and missiles against enemy fighters only on one or two occasions, with inconclusive results.
By June of 1967, only five squadrons of F-100s remained at home in the USA, most of the rest having been transferred to Vietnam to fight in the rapidly-escalating war. Although it encountered some maintenance difficulties, the F-100D proved remarkably adaptable to rough-field operations in the tropical heat and rain of Southeast Asia. For a time, F-100s enjoyed the best maintenance record of any aircraft in the Vietnam combat zone. However, as a tactical bomber, the F-100D was inferior to the F-105 and the F-4. The F-105 could carry a larger bomb load further and faster. In addition, the F-105 was built to take the extreme structural loads of low-level, high-speed flight, whereas the F-100 was not. Consequently, from mid-1965 onward, F-100D fighter bombers generally operated only in the South, leaving the North for the F-4 and the F-105. Down South, the F-100 turned out to be a very effective ground support aircraft, and beat back many enemy attacks.
Throughout the late 1960s and early 1970s, the F-100s were gradually withdrawn from combat in Vietnam and replaced by more capable types such as the F-105 and the F-4. The last F-100Ds left Vietnam in July of 1971.
The following Tactical Air Force Wings were equipped with the F-100D:
Following their withdrawal from Vietnam, numerous USAF F-100Ds were turned over to the Air National Guard. The ANG had actually gotten its first F-100Ds in 1969, with the 174th TFS of the Iowa ANG being the first receipient. However, the needs of Vietnam had caused the USAF to delay the handover of F-100Ds to the ANG, and by mid-1970 the ANG still had only 20. As the pace of the drawdown from Vietnam stepped up, transfers to the ANG began to accelerate, and by mid-1972, the Guard had gotten 335 F-100Ds.
The F-100D served with the following ANG squadrons:
The last F-100D was withdrawn from ANG service in 1979.
In early 1964, the Air Force Thunderbirds flight demonstration team began replacing their F-100Cs with Republic F-105 Thunderchiefs. This turned out to have been a mistake. A major F-105 flying accident in May of that year caused the USAF to decide to re-equip the Thunderbirds with eight F-100Ds modified for demonstration purposes. The USAF Thunderbirds flight demonstration team operated F-100Ds from July of 1964 until November of 1968, when they started to convert to the F-4E Phantom.
During an air show at Laughlin AFB in Texas on October 21, 1967, Thunderbird pilot Captain Merrill A. McPeak's F-100D (55-3520) disintegrated in midair during a solo demonstration. Fortunately, he was able to eject safely. The cause was traced to a catastrophic wing failure caused by a series of wing cracks that had been produced by metal fatigue. The Thunderbirds were temporarily grounded until their planes could be fixed. Some losses in Vietnam were also thought to have been caused by this problem rather than by enemy action, and the entire F-100D fleet was temporarily restricted to a 4-G maneuver limit until all the planes could be fixed by carrying out a complete modification of the wing structural box. These modifications were not completed until 1969.
A succession of in-service difficulties and problems beset the F-100D throughout its career. The safety record of the F-100D left a lot to be desired. Over five hundred were lost in accidents between mid-1956 and mid-1970, far more than were lost in combat in Vietnam. A lot of these accidents were due to pilot error, the F-100 being a relatively unforgiving aircraft, especially on landing. Compressor stalls were an big problem, as pilots would try to firewall the throttle too rapidly, producing a compressor stall.
F-100D 56-3440 is in storage at the Paul E. Garber Facility of the Smithsonian Institution in Suitland, Maryland.
An F-100D serial number 55-3754 in Thunderbirds markings is on display at the USAF Museum at Wright-Patterson AFB in Ohio.
54-2121/2132 North American F-100D-1-NA Super Sabre (NA-223) 54-2133/2151 North American F-100D-5-NA Super Sabre (NA-223) 54-2152/2221 North American F-100D-10-NA Super Sabre (NA-223) 54-2222/2303 North American F-100D-15-NA Super Sabre (NA-223) 55-2734/2743 North American F-100D-35-NH Super Sabre (NA-224) 55-2744/2783 North American F-100D-40-NH Super Sabre (NA-224) 55-2784/2863 North American F-100D-45-NH Super Sabre (NA-224) 55-2864/2908 North American F-100D-50-NH Super Sabre (NA-224) 55-2909/2954 North American F-100D-45-NH Super Sabre (NA-224) 55-3502/3601 North American F-100D-20-NA Super Sabre (NA-223) 55-3602/3701 North American F-100D-25-NA Super Sabre (NA-223) 55-3702/3814 North American F-100D-30-NA Super Sabre (NA-223) 56-2903/2962 North American F-100D-60-NA Super Sabre (NA-235) 56-2953/3022 North American F-100D-65-NA Super Sabre (NA-235) 56-3023/3142 North American F-100D-70-NA Super Sabre (NA-235) 56-3143/3198 North American F-100D-75-NA Super Sabre (NA-235) 56-3199/3346 North American F-100D-90-NA Super Sabre (NA-235) 56-3351/3378 North American F-100D-80-NH Super Sabre (NA-245) 56-3379/3463 North American F-100D-85-NH Super Sabre (NA-245)
Engine: One Pratt & Whitney J57-P-21/21A turbojet, 10,200 lb.st. dry and 16,000 lb.st. with afterburning. Dimensions: Wingspan 38 feet 9 inches, length 50 feet 0 inches, height 16 feet 2 3/4 inches, wing area 400 square feet. Performance: Maximum speed 770 mph at sea level (clean), 864 mph (Mach 1.3) at 36,000 feet (clean). Initial climb rate 19,000 feet/minute. An altitude of 35,000 feet could be attained in 2.3 minutes. Service ceiling 36,100 feet, combat ceiling 47,700 feet, absolute ceiling 50,000 feet. Normal range 534 miles, maximum range 1995 miles. Fuel capacity 1739 US gallons internally, total of 2139 gallons if maximum external fuel is carried. Weights: 21,000 pounds empty, 28,847 pounds gross, 34,832 pounds maximum takeoff. Armament: Four 20-mm Pontaic M-39 cannon. Six underwing pylons for up to 7040 pounds of bombs, fuel tanks, or rockets. A MK-28 or Mk-43/57/61 nuclear weapon could be carried. In later versions, four AIM-9B/E/J Sidewinder air-to-air infrared homing missiles could be carried.