When is single engine taxi not authorized?

Single engine taxi is not authorized when the Runway Visual Range (RVR) is less than 1200 feet because visibility conditions are critical for safe ground operations. When RVR drops below this threshold, the ability of the flight crew to assess the surrounding environment, including other aircraft and ground personnel, is significantly impaired. This could lead to unsafe maneuvering on the ground, increasing the risk of collisions or other ground incidents.

Under lower visibility conditions, it is crucial to have both engines operating to ensure optimal control and performance during taxi operations. This ensures that the aircraft can respond effectively to any potential hazards or obstacles that might not be visible due to reduced visibility.

Other conditions, such as braking action being good, temperatures above 15 degrees Celsius, or wet runway conditions, may allow for safe single engine taxiing under normal circumstances, as they do not inherently compromise the visibility or control needed for safe ground operations. Therefore, maintaining the highest level of operational safety and being vigilant regarding visibility conditions is vital, hence the prohibition on single engine taxi when the RVR is below 1200 feet.