The earlier iterations of the 'FSTA' were a 4-jet design. The earliest I saw was 'Solution 10'. Over the following years it changed to a 4 prop design, after about another 4 dozen 'solutions'.
The design was more or less fixed, then the fin and tailplane were redesigned and the prop rotation became 'down between engines'.
Engine and prop development was....protracted in both software and hardware elements. Single lever power controls with such a wide speed range from max thrust at brake release to idle thrust at max IMN presented huge problems - the 8 blade prop design is ingenious, but far from simple. Turbofans would, on balance, probably have been much simpler.
Last edited by BEagle; 17th May 2020 at 12:54.