XF5B-1

The Boeing XF5B‑1 was an experimental twin‑engine fighter‑bomber developed in the late 1930s as a response to the United States Navy’s demand for a high‑speed, carrier‑capable aircraft. First flown in June 1939, the XF5B‑1 employed two powerful Pratt & Whitney R‑1830 radials driving counter‑rotating propellers, which gave it a top speed of roughly 425 mph—unprecedented for a naval plane of its size. Its all‑metal construction featured a low‑wing monoplane layout, retractable landing gear, and a spacious cockpit with excellent visibility. The aircraft could carry up to 1,200 lb of bomb load internally and was equipped with .50‑caliber machine guns in the wings, allowing it to perform both air‑to‑air and air‑to‑ground missions. Although the XF5B‑1 never entered mass production, its innovative design influenced later Boeing fighters, most notably the P‑38 Lightning and the jet‑propelled X‑20 Dyna‑Soar concepts. The program demonstrated the feasibility of high‑performance twin‑engine naval aircraft and contributed valuable aerodynamic data that helped shape post‑war carrier aviation. Flight tests at Patuxent River showed a climb to 20,000 feet in under ten minutes and a service ceiling above 30,000 feet, proving the design’s high‑altitude capability. Its balanced thrust reduced torque, giving pilots stable handling during carrier operations.