Turn Performance & Stall Speed in a Bank
Load factor, turn radius and rate of turn at a bank and airspeed, how much the stall speed you enter rises in the bank, and the bank a standard-rate turn needs.
The g the wings carry at that bank, the radius and rate of the turn, the time round 360°, the stall speed in the bank from your level figure and the margin to it, and the bank angle for a rate you choose.
Example: 45° of bank at 120 kt: load factor 1.41, radius 1,275 ft, 9.1° per second; a 55 kt level stall speed becomes 65.4 kt; a standard-rate turn needs 18.2° (the rule says 19).
One over cosine,
square root of that.
Where the load factor comes from, why stall speed rises with it, how radius and rate follow from speed and bank, and what the rule for standard rate is.
Load factor
In a level turn the lift must both hold the weight and bend the flight path; its vertical part still equals the weight, so lift = weight ÷ cos φ and the load factor is n = 1 ÷ cos φ: 1.15 at 30°, 1.41 at 45°, 2 at 60°. The wings, and the occupants, feel n times the weight.
Stall speed in the bank
Lift is proportional to the square of the speed, so the speed at which the wing can just produce n times the weight is Vs × √n — 41 % higher at 60°. The level stall speed depends on weight, configuration and centre of gravity, which is why the page takes yours from the handbook rather than storing one.
Radius, rate and standard rate
The horizontal part of the lift provides the centripetal force: radius = V² ÷ (g × tan φ) and rate of turn = g × tan φ ÷ V. A standard-rate turn (3° per second, two minutes round) therefore needs a bank of atan(ω × V ÷ g), steeper the faster you fly; the “airspeed in knots ÷ 10 + 7” rule is shown beside the exact angle for the 3°/s case.
What the number does not settle
A coordinated, level, constant-speed turn; slipping, skidding, climbing or descending turns and the aircraft’s limit load factor are not modelled. A planning aid, not a substitute for the pilot’s operating handbook, the aircraft’s limitations or the rules that apply to the flight. Inputs stay in your browser; the same anonymous usage counts as the rest of the site apply.