Hey everyone some people might know this some might not but i found it very interesting, i was reading a topic where people were imagining the new GE 777X engines on a twin jet 747 and i just wanted to mention that boeibg came close to a non 4 engined 747 below is concept images and a back story about it from boeing-747.com:
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.
Tbh this is how i found out why they made the 747sp :)
It just shows the ideas boeing had for this marvellous aircraft:)