Final answer:
Switching to an alternate static source affects altimeter and airspeed indicator readings due to different static pressure, which also impacts the Vertical Speed Indicator (VSI) showing an initial climb even in level flight.
Step-by-step explanation:
When switching to an alternate static source for instrumentation like the altimeter and airspeed indicator, there are changes in readings due to the different static pressure at the alternate port.
The Vertical Speed Indicator (VSI), which measures the rate of climb or descent, is also affected because it relies on static pressure changes to function.
With the alternate static source, which typically reads a slightly lower static pressure, the altimeter will show a higher altitude than actual, the airspeed indicator will show a higher airspeed than actual, and the VSI may initially show a climb even if the aircraft maintains level flight.
This is after the change; there is no remaining inaccuracy once the pressure stabilizes.