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Feather, Et Al:
Constant speed, constant altitude turns are verrrry interrrresting!
From "Aerodynamics for Naval Aviators", at a speed X, it is the minimum speed necessary to aerodynamically reach the limit load factor to produce the minimum turn radius. This is constrained to subsonic flight at lower altitudes. At lesser speeds, the max load factor is not reachable and at greater speeds, one is structurally limited. So,
X = level flight stall speed times the square root of the limit load factor.
If the load factor is limited to 4 then X is twice the stall speed. Say a 320 stalls at 60 Kts, the minimum turn radius would be at 75 degrees. But, this is also close to the stall speed for such a level turn. (Load factor = 1 over the cosine of the bank angle). Furthermore, consider that there is a considerable increase in induced drag for high bank angles. 30 degrees is a 33% increase, 45 degrees is a 100% increase and 60 degrees is a 300% increase. Thus the need for POWER to maintain a constant speed, constant altitude turn.
Note the following: r = (V x V) / (11.26 x TAN(angle)) where r is the turn radius in feet, V is the KTAS, and angle is the bank angle.
Also: ROT = (1091 x TAN(angle)) / V where ROT is the rate of turn in degrees per second.
So, for a given speed, greater bank angle reduces the radius and increases the ROT.
In "Aircraft vs Aircraft", a maneuver is described which allows an in-trail attacking aircraft with poorer turn performance than the attackee to actually turn inside and remain in trail. The maneuver is to pull up (thus slowing down), making a sharp banked turn, and diving back down inside the level turn of the attacked, thus avoiding an overshoot of trying to out turn the enemy. If you could see me, I could show you this maneuver with my hands.
However, I asked Darryl Greenameyer if he did this at Reno. He said "No, I want to keep the pylon at eye level so I don't cut it."
Fuel for thought.
Grayhawk
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