Which of the following is true about air-driven gyros?

• A. They have no reliability issues.
• B. They have reduced RPM with reduced density.
• C. They never require maintenance.
• D. They are not affected by vibration.

Answer: (B)

Air-driven gyros rely on a steady flow of air supplied by an engine-driven pump to spin the gyro rotor. The amount of air flowing through the system depends on air density, because denser air carries more mass per unit volume than less dense air. As you climb and the atmosphere thins, the air density drops. For the same pump speed and pressure differential, the mass flow through the gyro decreases, so the rotor spins more slowly. That slower rotor speed can lead to slower response and potential indication lag, especially during dynamic flight.

This is why the statement about reduced density causing reduced rotor RPM is the best answer. The other options imply reliability, maintenance, or vibration immunity that aren’t true for air-driven gyros—these systems do require proper maintenance, can be affected by leaks or blockages, and are sensitive to vibration—so those ideas don’t describe how air-driven gyros actually behave.