Re: Why no FSW on Comercial plane?

A commercial FSW isn’t a specifically good idea for a large airliner for some of the reasons stated above.

People often discuss the FSW its efficiency, etc. among some of the problems that plague the FSW is the problem with the wingtip. In a BSW the turbulence move away from the fuselage, where it can be controlled more easily. With the FSW, the air flow moves towards the fuselage. Back at the wingtip, the additional lift can cause problems not encountered with other wings. The outer wing in its flexing has a bad tendencies of when torque is applied to the outer wing, the leading edge lifts and the wing can rupture and tear off the outer ⅓ of the wing!

There are definite reasons the NASA & Germany explored the X-29 and Russia with Su-47. These two programs went no further than the testing stage! These planes provideded data but, that is it.

The 3-engined aircraft arose due to mis-matched aircraft size to available engine thrust.

United Air Line’s major hub of operations was in Denver, Co. They needed a jetliner that could take-off from Denver’s International air port. At temperatures at or above 95°, the runways are at an altitude of 5,280-ft. above sea level and, at the maximum take-off weight!
Engines at the time did not produce enough thrust for just two engines to be the solution. So the usage of three engines were used to meet these specs. Plus, the engines near the center-line of the airliner, tends to encounter less problems when one engine has to be shut down. I am not sure whether it was either UAL or Boeing that proposed a three engine airliner. Boeing’s met the specs and produced the B-727 mainly for a nitch market, smaller than the B-707 type airliners and larger than the B-737 that was in development.