FAA Commercial Pilot Airplane (CAX)Aerodynamics and PerformanceMedium
An airplane is in a coordinated turn with a true airspeed of 150 knots and a 45° angle of bank. Using the turn radius formula r = V²/(11.26 × tan(bank)), what is the approximate radius of turn?
- A2,500 feet
- B1,000 feet
- C2,000 feet
- D1,500 feet
Show answer & explanationAnswer & explanation
Correct answer: C. 2,000 feet
r = V²/(11.26 × tan(45°)) = 150²/(11.26 × 1.0) = 22,500/11.26 ≈ 1,998 feet, which rounds to approximately 2,000 feet.
Why the other options are wrong
- A. This overestimates the radius for these conditions.
- B. This underestimates the radius; it does not match the formula's result.
- D. This value is too small for the given TAS and bank angle.
Turn Radius Calculation
Turn radius depends on the square of true airspeed and inversely on the tangent of the bank angle: r = V²/(11.26 × tan(bank)).
- Radius increases with the square of TAS
- Steeper bank angle decreases radius
- Formula uses TAS in knots, radius in feet
- Doubling speed quadruples radius at constant bank
Memory trick: Speed squared makes circles spread — faster means wider bend!