min radius turn occurs at Va [Vp] It gives both the minimum speed required developing the aerodynamic load factors required for min radius turns and the maximum within the limits of strength
less than Va the limit load factors aren't available.... and the min radius can't be developed----aerodynamic limits
. . .
fooling with flaps is not too good because even though stall speeds are less, so are limit loads....watch it!
While you may be correct for some airplanes in the instantaneous case, I don't think you would prevail for the sustained (180 deg turn) case. A few questions:
1) What civil aircraft can sustain Va at max allowable G and constant altitude? [I believe the answer is "None."]
2) What is the airspeed bleed rate, when starting at Va in a max G turn, for the airplane under discussion? [Yes, rhetorical, because it depends on the specific case.]
3) At what rate does the pilot have to relax G so he doesn't stall when the airspeed bleeds off? [Again, rhetorical for the same reason.]
4) If the alternative is colliding with a mountain, are you willing to overstress the airplane to minimize your turn radius? If the answer is "Yes," you may find that a 2.5 G turn (instead of the 2.0 G clean limit), 10 knots slower than clean speed, with 20 deg flaps, may give you the turn radius margin needed to miss that mountain.
5) If you start the turn with "excess" airspeed, using the vertical plane in a wingover maneuver will significantly reduce the turn radius. Again, power and altitude available may limit vertical maneuverability.
I'm convinced! the maths are in the first link BOAC posted.
OK... What part of "r = V**2 / (g * tan(b)" (from that page) don't you understand?
The square of the velocity is the most significant term! Let's assume Va is 100 mph, a clean turn can be made at 70 mph, and a flaps-down turn can be made at 60 mph.
At Va and 3.8g (74 deg bank; cited by someone to be the limit), turn radius is 1521 per the formula (units are unknown and irrelevant; I'm speaking only relatively).
At 70 mph and 2.5 G, the radius is 856!
At 60 mph and 2 G, the radius is 1040; Reduce it to 628 if you can sustain 2.5 G!
So, either a clean turn at 66.5 deg bank or a flaps-down turn at 60 deg angle of bank will yield a smaller turn radius than the turn at Va and max G -- even disregarding sustainability!
Granted, reducing G by putting the flaps down will increase the turn radius. However, if you can sustain the same G as at a minimum speed clean turn, you come out ahead, with little risk of pulling off the wings (acknowledging the 150% design factor).