NB-4

The Boeing NB‑4 was a modest‑size, twin‑engine transport and training aircraft that emerged from Boeing’s low‑cost utility program in the early 1960s. Designed as a replacement for the aging NB‑2, the NB‑4 first flew on 12 March 1964 from Seattle’s Paine Field. Only fifteen airframes were built; three served as prototype testbeds for new composite wing panels, and the remainder entered service with the United States Air Force’s 12th Flight Training Squadron and several foreign air forces under the Mutual Defense Assistance Act.

Key features included a semi‑monocoque aluminum‑lithium fuselage, trapezoidal wings with integral fuel tanks, and two Pratt & Whitney PT6A‑27 turboprop engines delivering 750 shaft horsepower each. The cockpit featured first‑generation digital flight‑management computers and a glass panel display, giving cadets exposure to avionics later seen in the C‑17 and 737 families. Its short take‑off and landing capability allowed operation from austere airstrips, and low operating cost made it popular for pilot instruction and light cargo missions.

Although retired in 1992, the NB‑4’s experimental use of composites and digital avionics paved the way for Boeing’s later high‑performance transports, cementing its quiet but important role in modern aviation.