Boeing 747History, variants & specifications

Boeing 747 Trijet

Concept art for the unbuilt three-engined Boeing 747.

Concept artwork for a three-engined 747, studied in the late 1960s and early 1970s against the Lockheed L-1011 and McDonnell Douglas DC-10.

The centre engine would have sat in the tail with an S-duct intake. It was never built: the structural work needed to carry an engine in the fin, on an aircraft designed around four wing-mounted ones, was substantial. More on the 747 trijet.

  • Concept artwork of a three-engined Boeing 747 with a tail-mounted centre engine
    During the late 1960s and early 1970s, Boeing studied the development of a shorter 747 with three-engines to compete with the smaller L-1011 TriStar and DC-10. The 747 trijet would have had more payload, range and passenger capacity. The center engine would have been fitted in the tail with an S-duct intake similar to the L-1011's. However, engineering studies showed that a total redesign of the 747 wing would be necessary. Maintaining the same 747 handling characteristics would be important to minimize pilot retraining. Boeing decided instead to pursue a shortened four-engine 747 that resulted in the 747SP. In the 1990s, the Boeing 777, a long range twinjet airliner smaller than the 747-400 entered service in the market where the 747-300 had been targeted.

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