What condition prohibits takeoff regarding fuel quantity gauges?

The condition that prohibits takeoff regarding fuel quantity gauges is when the fuel quantity is in the yellow arcs. The yellow arc typically indicates a cautionary range where fuel levels may be low and not within the safe limits for takeoff. This is critical, as insufficient fuel can lead to engine performance issues or complete engine failure during flight, which could be catastrophic.

Monitoring fuel levels is essential, and pilots must ensure that fuel quantities are adequate before initiating takeoff. The other ranges, represented by colors like green (safe), red (critical out of limits), and blue (usually indicates a standby or alternate range), do not specifically denote a prohibition. The yellow range serves as a warning which, if exceeded, implies that operations should be halted until fuel levels are raised into the green arc, ensuring safe flight operations.