FAA Jeppesen Instrument Rating Practice Test 2025 – Your Complete Exam Prep

When switching to an alternate static source, the airspeed, altimeter, and vertical speed indicator (VSI) may temporarily show higher airspeed, higher altitude, and the VSI might indicate a climb. This occurs because when the alternate static source is used, it often draws air from a location that may not be subject to the same static pressure as the primary source.

If the alternate static source is located in a different pressure area, especially in turbulent conditions, this can lead to variations in the readings. The static pressure may be lower when the alternate source is used, which affects the altimeter reading and potentially causes it to read a higher altitude than it actually is. In addition, the VSI may indicate a climb because it responds to changes in static pressure. If the pressure is lower than what the primary source was reading, the VSI could misleadingly indicate a climb.

The reasoning behind the other options revolves around the basic understanding of how static pressure affects instrument readings, where the nuances of pressure differentials can lead to such variations. Understanding the behavior of instruments during this switch is crucial for a pilot's situational awareness, especially in conditions where accurate altitude and airspeed readings are necessary for safe navigation and operations.