Aerodynamic Turning Model
Dick,
The 'mushing' is a speed loser because it dramatically increases drag. If it were beneficial to increase the turn radius, it would need to be done with minimum drag. It is certainly true that, all other things being equal, an aircraft can maintain a higher airspeed in a large radius turn than a small radius turn. This is for two reasons. The first is simply that tighter turns require more acceleration of the airplane's mass toward the 'axis' of the turn, which consumes more power, which costs airspeed. The second is that the additional lift and AoA needed for a tight turn generate more drag than a wide turn, even if we optimize it. The reason that this doesn't push us toward wide turns is that maximum airspeed is not our goal: fastest completion of the turn is our goal. I don't know what the theoretical optimum solution is for minimum turning time, but my guess is that it is something like: "make the tightest turn you can without incurring an excessive drag penalty". Possibly you would run into structural constraints as the turns get tighter, but my gut tells me that we can make these things so strong that drag ( profile drag ) is enemy #1.
banktoturn