If the vacuum system in an aircraft fails, which instruments would a pilot lose?

When analyzing the failure of a vacuum system in an aircraft, it is crucial to understand which instruments rely on this system for their operation. The attitude indicator and heading indicator are both sensitive to changes in air pressure and rely on a vacuum source to function correctly.

The attitude indicator requires a gyroscope that spins rapidly to determine the aircraft's orientation relative to the horizon, while the heading indicator also utilizes a gyro system to maintain accurate directional information. If the vacuum system fails, both of these gyroscopic instruments will become inoperative, leaving the pilot without crucial data on the aircraft's position and direction.

In contrast, the other instruments listed do not rely on a vacuum source. For example, the altitude indicator works with static air pressure, the vertical speed indicator also uses static pressure, and the airspeed indicator measures dynamic pressure. The turn coordinator provides information through its own electrical systems and also does not depend on a vacuum. Therefore, when the vacuum system fails, it is the attitude and heading indicators that would no longer provide reliable information to the pilot.