FAA Commercial Pilot Airplane (CAX)Aerodynamics and PerformanceEasy
A pilot is flying a high-performance airplane at a constant indicated airspeed (IAS) and bank angle during a climbing turn. As the airplane gains altitude, what effect will this have on the true airspeed (TAS) and the radius of the turn?
- ATAS will increase, and the turn radius will decrease.
- BTAS will decrease, and the turn radius will increase.
- CTAS will increase, and the turn radius will increase.
- DTAS will decrease, and the turn radius will decrease.
Show answer & explanationAnswer & explanation
Correct answer: C. TAS will increase, and the turn radius will increase.
At a constant indicated airspeed, true airspeed increases with altitude due to decreasing air density. A higher true airspeed directly results in a larger turn radius for a given bank angle.
Why the other options are wrong
- A. Incorrect, while TAS increases, a larger TAS always leads to a larger turn radius at a constant bank.
- B. Incorrect, TAS increases with altitude at constant IAS, and greater TAS increases turn radius.
- D. Incorrect, TAS increases with altitude at constant IAS, and greater TAS increases turn radius.
TAS vs. Altitude at Constant IAS
True airspeed (TAS) increases with altitude when indicated airspeed (IAS) is held constant, because the air density decreases, requiring a higher true speed to generate the same dynamic pressure.
- IAS measures dynamic pressure, not true speed.
- As air density drops, a greater TAS is needed for the same dynamic pressure.
- Higher TAS at constant bank angle means a larger turn radius.
Memory trick: As you climb higher, the air thins, making your true speed faster for the same indicated speed, stretching your turn.