FAA Commercial Pilot Airplane (CAX)Aerodynamics and PerformanceHard
A pilot maintains a constant indicated airspeed and a constant 45° bank angle while climbing from 5,000 feet to 25,000 feet density altitude in a coordinated turn. How do the turn radius and rate of turn change during this climb?
- ATurn radius and rate of turn both remain unchanged
- BTurn radius decreases; rate of turn also decreases
- CTurn radius decreases; rate of turn increases
- DTurn radius increases; rate of turn decreases
Show answer & explanationAnswer & explanation
Correct answer: D. Turn radius increases; rate of turn decreases
At constant IAS, decreasing air density with altitude causes true airspeed to increase. Since turn radius is proportional to V² and rate of turn is inversely proportional to V (at a fixed bank angle), an increase in TAS causes the turn radius to increase and the rate of turn to decrease.
Why the other options are wrong
- A. Both values change because TAS increases significantly with altitude.
- B. Turn radius does not decrease; it increases as TAS rises.
- C. This reverses the actual relationship between TAS and turn performance.
Altitude Effects on Turn Performance
As altitude increases at a constant indicated airspeed, true airspeed rises due to lower air density, which increases turn radius and decreases rate of turn for a given bank angle.
- TAS increases with altitude for constant IAS
- Turn radius ∝ V², so it grows quickly with TAS
- Rate of turn ∝ 1/V, so it decreases as TAS rises
- Pilots must bank steeper at altitude to maintain the same turn radius/rate
Memory trick: Higher you fly, wider you turn, slower you spin — TAS makes the difference within!