The failure of the F3H-1N would ordinarily have been fatal for the entire Demon project. However, shortly after the first prototype had flown, McDonnell management had already become alarmed at the deficiencies of the Westinghouse J40, and had the foresight to consider alternative powerplants just in case the J40's problems proved to be incurable.
Back in November of 1952, even before the first production F3H-1N had flown, McDonnell had asked the Navy for permission to consider adapting the Demon to a different engine. The Navy was initially hesitant to approve this change, since they had committed themselves to using the J40 in most of the Navy's advanced combat aircraft projects of the period. However, the Bureau of Aeronautics eventually relented and authorized McDonnell to begin studying the feasibility of using the more-powerful Allison J71 in the Demon. The J71-powered Demon was designated F3H-2N.
A mockup of the F3H-2N was inspected in August of 1953. In November of 1953, the F3H-1N contract was amended to call for the completion of the 32nd and 34th F3H-1N aircraft (BuNos 133520 and 133522) as J71-powered prototypes. In addition, the design was to be reworked from what was basically a night fighter into an all-weather multipurpose aircraft. This idea met with Navy approval, and the contract was amended so that the 61th and subsequent production Demons would be powered by the J71.
In order to accommodate the increased weight due to the adaptation of the Demon night fighter into an all-weather general-purpose fighter, the F3H-2N was to be fitted with larger wings, with an area increased from 442 to 519 square feet. This was done by extending the chord at the wing root by 40 inches and by moving the trailing edge aft.
The first F3H-2N prototype (BuNo 133520) flew on April 23, 1955. The first production F3H-2N flew in June of 1955. A total of 140 production aircraft which had been ordered as F3H-1Ns were delivered as F3H-2Ns with J71-A-2 engines. The J71-A-2 was rated at 10,000 lb.st. dry and 14,400 lb.s.t. with afterburning. In service, these engines were replaced by similarly-rated A-2A or A-2B versions.
The F3H-2N carried an AN/APG-51 airborne intercept radar set. The armament consisted of four 20-mm cannon mounted below and behind the air intakes. Two hardpoints were provided underneath each wing. In addition, two 262-gallon drop tanks could be carried on mounts underneath the fuselage. Later, many F3H-2Ns were retrofitted to carry four AAM-N-7 Sidewinder air-to-air missiles. In later years, the upper two cannon were often omitted when external stores or missiles were carried, the blast tubes being faired over.
The F3H-2M (M for "Missile") was a version of the F3H-2N that was equipped to carry and launch the AAM-N-2 Sparrow I radar beam-riding air-to-air missile. The F3H-2M was produced in parallel with the F3H-2N, but was modified to carry the AN/APG-51B radar set that was used to guide the Sparrow I missile. Four of these Sparrow missiles could be carried underneath the wings. The first F3H-2M flew on August 23, 1955. The F3H-2M was produced in parallel with the F3H-2N, 80 examples of the F3H-2M being built.
The F3H-2P was a proposed reconnaissance variant of the J71-powered Demon, with the radar and the armament being replaced by camera installations. The F3H-2P had been originally been proposed as the replacement for the abortive J40-powered F3H-1P project, but the F3H-2P project was itself cancelled before anything could be built.
The F3H-2N and -2M were all built under contracts initially intended to cover the abortive F3H-1N. Following the completion of these contracts, a new Demon version was ordered in 1956-57 under a new set of contracts. This version was designated F3H-2 (with no suffix). The F3H-2 could carry and launch the more capable AAM-N-6 (AIM-7C after September 1962) Sparrow III semi-active radar homing missile. The Sparrow III was a definite improvement over the Sparrow I, which was a pure beam riding missile, with no active homing capability, which meant that the guidance error was in the shape of a cone, which increased in diameter as the range inceased. The F3H-2 could also launch the AAM-N-7 (AIM-9B) Sidewinder IA air-to-air infrared homing air-to-air missile. The F3H-2 was equipped with an AN/APG-51B radar along with the AN/APA-127 Illuminator/Launch Envelope computer. The F3H-2 was optimized as a strike fighter and could carry up to 6000 pounds of ordnance (bombs, rockets, or "special stores") on two fuselage and six wing stations. The F3H-2 also differed from the previous versions in having a slightly shorter beaver tail cone. The last of 239 F3H-2s was delivered on April 8, 1960, bringing the Demon production program to a close. Total Demon production was 519 aircraft.
Some F3H-2Ns were retrofitted for Sparrow III semi-active radar homing missiles, and were redesignated F3H-2N/2. The F3H-2Ms were never upgraded for Sparrow III capability.
The Sparrow II was a fully-active radar homing missile, but it was never used on F3H's.
The J71-powered Demon entered Navy service during the first quarter of
1956. In February of that year, an F3H-2M was delivered to the Naval
Missile Center at Point Mugu in California. In March, F3H-2Ns were
delivered to VC-3, a development and training squadron based at NAS
Moffett Field in California, and to VF-14, an operational squadron
based at NAS Cecil Field in Florida.
F3H-2Ns first went to sea with VF-14 aboard the USS *Forrestal*
(CVA-59) when it deployed to the Mediterranean from January to July of
1957. Demons ultimately served with 22 Navy squadrons as follows:
VF-13, VF-14, VF-31, VF-41, VF-61, VF-82, VF-131, VF-161
VF-21, VF-24, VF-53, VF-54, VF-64, VF-92, VF-112, VF-114, VF-122, VF-124, VF-141, VF-151, VF-193, VF-213
In addition, Demons also served with two replacement training squadrons (VF-101 and VF-121), with two evaluation squadrons (VX-3 and VX-4), and with one composite squadron (VC-3).
The F3H-2N could carry drop tanks on two hardpoints underneath the fuselage. However, aerodynamic drag was excessively high because the two tanks were so close together. Consequently, the pair of drop tanks were rarely carried, or else, only one was carried. Beginning in 1955, a removable refuelling probe was attached to the starboard side of the fuselage above the intake. It could be extended upward and outward during air refuelling.
One F3H-2N (BuNo 133573) was modified in 1957 as a flying test bed for the AN/APQ-50 radar set intended for the F4H-1 Phantom II.
On September 18, 1962, the US Department of Defense combined all Air Force and Navy aircraft designations into the existing Air Force system. A new F-for-fighter series was begun, and Navy and Marine Corps fighters were redesignated to fit in with the new system. The F3H-2N was redesignated F-3C, the F3H-2M became MF-3B, and the F3H-2 became F-3B. The designation F-3A was never assigned, probably being a reflection of the unfortunate F3H-1N which never entered service.
The J71-powered Demon proved to be fairly popular with its crews. They liked its large wings with power-operated slats, and they especially liked its docile handling at high altitudes as well as its good handling during carrier landings. However, the Demon had rather short legs and had a relatively low endurance, even when carrying no external stores. Consequently, the F3H-2 Demon was not often used in its intended general-purpose role. In addition, the Demon was still somewhat underpowered even with the J71 engine, and the two upper cannon were often omitted to save weight, especially when missiles or external stores were carried.
Because of its long gestation period, the J71-powered Demon entered service with the Navy relatively late in the game, and its service career was rather short. After only a few years, Demons were replaced in service by Vought F-8 Crusaders and McDonnell F-4 Phantoms. VF-161 was the last Navy squadron to use the Demon. It finally traded in its F-3Bs for F-4Bs in September of 1964. Most Demons went into storage or were scrapped, although a few examples remained in various test roles for several years thereafter.
Serials of the F3H-2N, F3H-2M, and F3H-2:
133520 McDonnell F3H-2N Demon 133522 McDonnell F3H-2N Demon 133549/133568 McDonnell F3H-2N Demon 133569 McDonnell F3H-2M Demon 133570/133622 McDonnell F3H-2N Demon 133623/133638 McDonnell F3H-2M Demon 136966/136999 McDonnell F3H-2N Demon 137000/137032 McDonnell F3H-2N Demon 137033/137095 McDonnell F3H-2N Demon 137132/137155 McDonnell F3H-2P Demon - contract cancelled 143403/143492 McDonnell F3H-2 Demon - originally ordered as F3H-3 145202/145306 McDonnell F3H-2 Demon 146328/146339 McDonnell F3H-2 Demon 146709/146740 McDonnell F3H-2 Demon
Engine: One Allison J71-A-2 engine, rated at 10,000 lb.s.t. dry and 14,400 lb.s.t. with afterburning. Performance: Maximum speed 716 mph at sea level, 643 mph at 35,000 feet. Initial climb rate: 14,350 feet per minute. Service ceiling: 42,650 feet. Normal range: 1180 miles, maximum range 1370 miles. Weights: 21,287 pounds empty, 31,145 pounds loaded, 39,000 pounds maximum takeoff. Dimensions: wingspan 35 feet 4 inches, length 58 feet 11 1/2 inches, height 14 feet 6.6 inches, wing area 519 square feet. Armed with four 20-mm cannon. A total of 6000 pounds of external ordinance could be carried on four under-wing stations and two under-fuselage stations.