During RNAV approach guidance, which control is ignored by the system?

• A. Altitude preselector
• B. Airspeed indicator
• C. Vertical speed
• D. Attitude indicator

Answer: (A)

RNAV approach guidance provides a defined lateral path and vertical profile from the navigation database, and the system follows that published path to meet each altitude constraint along the approach. The vertical guidance (VNAV) overrides any manual altitude target, so the altitude preselector isn’t used to steer the descent during the RNAV approach. In other words, the approach’s step-down altitudes dictate where you should be, and the system will descend accordingly, ignoring the altitude you might have set on the altitude preselector. The other indicators and controls—airspeed, vertical speed, and attitude—remain active for monitoring and controlling performance and attitude, but they do not override the RNAV path’s altitude constraints.