The 'Lead Sled' that paved the way for the Phantom II

Countries & Cities · Published 13 October 2026 Swipe more like this →

In short: The McDonnell F3H Demon was a naval fighter born of desperation. Designed to counter the Soviet MiG-15, it became a political and engineering nightmare, burdened by weight and unreliable engines. Yet, despite its flaws, it served as the direct ancestor to one of the most iconic jets in history.

Developed in the late 1940s, the Demon was the U.S. Navy's first swept-wing jet fighter. It was originally envisioned as a short-range day fighter, but the unexpected combat debut of the Soviet MiG-15 during the Korean War forced a radical redesign. To meet the need for an all-weather interceptor, the Navy added approximately 7,000 lbs of weight to an airframe that originally weighed 22,000 lbs. This massive increase severely hampered the aircraft's performance, leading to its colloquial nickname, the "lead sled."

The project was plagued by the Westinghouse J40 engine, which was promoted by Navy officials but proved to be a "fiasco." It produced only half the promised thrust and suffered from frequent compressor stalls. The failure was so significant that Time magazine highlighted the loss of 21 unflyable planes and $200 million in costs. Eventually, the program was abandoned in 1955, forcing a major redesign to accommodate the Allison J71 engine. This new version, the F3H-2N, entered service in March 1956.

While the Demon was criticized for its power-to-weight ratio, it was noted for its stability and ease of handling during carrier operations. It was also one of the first American aircraft primarily armed with missiles rather than cannons. Its legacy is cemented by its lineage: the F-4 Phantom II, which replaced the Demon in 1964, was conceived as an advanced development of a proposed "Super Demon."

The aircraft served as the Navy's front-line fighter until 1962. Despite its role in the Cold War, it never claimed any aerial victories in dogfights or with missiles, though it did fly reconnaissance and combat air patrols over Lebanon and Quemoy in 1958.

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