General Authority of Civil Aviation (GACA) Aeronautical Information Publication (AIP) Practice Exam

What is the turbulent air penetration speed at or above 25,000 feet, combining speed and Mach considerations?

1. 270 Knots

2. 0.80 Mach

3. 280 Knots or 0.82 Mach, whichever is lower

4. 0.85 Mach

The correct answer is: 280 Knots or 0.82 Mach, whichever is lower

The turbulent air penetration speed at or above 25,000 feet entails a consideration of both indicated airspeed (measured in knots) and true airspeed (expressed in Mach). The correct answer includes a specific limitation that ensures safety during such conditions. The combination of a maximum airspeed in knots or a maximum Mach speed provides critical guidance for pilots operating in turbulent environments. This is important because as altitude increases, air density decreases, affecting how speeds are interpreted. The aim is to maintain a balance between controlling structural stress on the aircraft and ensuring maneuverability in turbulence. Choosing the lower of the two values is crucial since it ensures that the aircraft does not exceed structural limitations and maintains safe operational parameters without risking the onset of damaging turbulence effects. Therefore, setting the turbulent air penetration speed to 280 knots or 0.82 Mach, whichever is lower, provides an optimal safety cushion while allowing for effective aircraft operation. The other choices do not incorporate this twofold consideration of both speed and Mach appropriately. Some may suggest fixed speed values that do not adjust with altitude, whereas others exceed the recommended Mach limitations for safety during turbulence. Thus, the correct choice effectively balances these two critical factors for operations in turbulent air at high altitudes.