The McDonnell F3H Demon had its origin in a Request for Proposal issued by the US Navy Bureau of Aeronautics on May 21, 1948 for a carrier-based interceptor. In the RFP, the Navy was looking for a carrier-based interceptor with a performance equal or superior to that of the most advanced land-based fighters then entering service.
The F3H design effort at McDonnell was led by Richard Deagen. At that time, the Navy was pushing the Westinghouse-designed afterburning J40 turbojet as the powerplant of choice for its next generation of advanced warplanes. Yielding to Navy pressure, McDonnell departed from its previous design philosophy of using twin-engined configurations and decided to adopt a single J40 as the powerplant for its entry, which was designated Model 58 by the company. The Model 58 called for a single-engine, single-seat day fighter with lateral air intakes and a 45-degree sweptback wing and tail surfaces.
Eleven competitors submitted designs in response to the RFP, among them being McDonnell's Model 58. In December of 1948, the McDonnell design was declared the winner of the competition, and on January 3, 1949 an initial Letter of Intent was issued covering the initial design. The designation XF3H-1 was assigned.
The competing Douglas design called for a delta-winged carrier-based aircraft. It was also to be powered by the J40 engine. It came in second in the competition, and was deemed sufficiently promising that the Navy issued a contract for two prototypes under the designation XF4D-1.
A mockup of the XF3H-1 was inspected between July 13 and 15, 1949. Following some redesign in order to save weight, two XF3H-1s were ordered on September 30, 1949.
The F3H had originally been proposed strictly as a day fighter. While the XF3H-1 prototypes were under construction, the Navy changed its mind and directed that production versions of the Demon be designed as general-purpose all-weather fighters. The designation of this production version was to be F3H-1N.
A modified F3H-1N mockup incorporating these changes was inspected in July of 1951. Work on the two prototypes was not affected, as they were seen simply as aerodynamic test vehicles rather than operational test aircraft. However, the sudden change in direction did delay the Demon program significantly.
In the summer of 1951, the first XF3H-1 (BuNo 125444) was finally ready for its first flight. Since the intended 9200 lb.s.t. afterburning Westinghouse J40-WE-8 was not yet available for installation, a non-afterburning 5600 lb.s.t. XJ40-WE-6 was fitted in its place. The XF3H-1 took off on its maiden flight on August 7, 1951, Robert M. Edholm being at the controls. The second prototype (BuNo 125445) followed in January of 1952.
The J40 turbojet proved to be totally unreliable during flight testing. In August of 1952, the first prototype was damaged in a landing accident following an inflight engine failure. Both prototypes were temporarily grounded on two occasions because of engine problems. In addition, early flight testing turned up problems with poor forward visibility, an excessively-slow roll rate, and inadequate lateral stability. A redesign of the nose section on production models cured the visibilty problem. The roll rate problem was cured by moving the ailerons further inboard, with a corresponding decrease in the length and area of the trailing-edge flaps. The lateral stability was improved by removing the wing fence from each outboard wing panel. An autopilot was added.
The second prototype was fitted with a 10,500 lb.s.t. afterburning J40-WE-8 in January of 1953. This engine did not prove to be any more reliable than the non-afterburning WE-6. This aircraft was used for preliminary evaluation tests at the Naval Air Test Center at Patuxent, Maryland beginning in August of 1953. In October of 1953, the second XF3H-1 was used for initial carrier trials aboard the USS *Coral Sea* (CVA-43). These trials were fairly successful, but there were some problems with low visibility during carrier approach and landing.
The first XF3H-1 was lost in a crash on March 18, 1954, following an inflight engine explosion. The second prototype was permanently grounded shortly thereafter. It was later shipped to the Naval Air Development Center at Johnsville, Pennsylvania to be used in barrier engagement tests.
125444/125445 McDonnell XF3H-1 Demon