FAA Commercial Pilot Airplane (CAX)Aerodynamics and PerformanceHard
An airplane is flown in a coordinated turn at a true airspeed of 180 knots with a 50° angle of bank. Using r = V²/(11.26 × tan(bank)), what is the approximate turn radius (tan 50° ≈ 1.19)?
- A1,800 feet
- B2,800 feet
- C2,100 feet
- D2,400 feet
Show answer & explanationAnswer & explanation
Correct answer: D. 2,400 feet
r = 180²/(11.26 × 1.19) = 32,400/13.4 ≈ 2,418 feet, which rounds to approximately 2,400 feet.
Why the other options are wrong
- A. This underestimates the radius for the given TAS and bank angle.
- B. This overestimates the radius beyond the calculated result.
- C. This is closer but still below the calculated value.
Turn Radius at High TAS
Because turn radius is proportional to the square of true airspeed, even modest speed increases significantly enlarge the turn radius at a constant bank angle.
- r = V²/(11.26 × tan(bank))
- Radius grows with the square of TAS
- Steeper bank reduces radius for the same speed
- High-speed aircraft need much steeper banks to match small-radius turns
Memory trick: Square the speed, then watch your circle spread!