What effective runway length is needed for a turbojet-powered airplane if the runways are forecast to be wet at the ETA?

The correct choice regarding the effective runway length needed for a turbojet-powered airplane when the runways are forecast to be wet at the estimated time of arrival (ETA) is the requirement of 115 percent of the length needed for a dry runway.

When a runway is wet, it significantly affects the aircraft’s braking performance. Wet runway conditions generally require longer distances for both takeoff and landing due to reduced friction. Regulatory guidelines and safety practices often suggest increasing the required runway length to account for these conditions, and a multiplier of 115 percent is commonly used to ensure that the aircraft can safely operate under such circumstances.

Using this multiplier acknowledges the added safety margin needed for the transitional phase in performance as the aircraft reacts differently when interfacing with a wet surface compared to dry conditions. This precaution ensures that pilots and dispatchers are adequately prepared for performance considerations under varying atmospheric and surface conditions, promoting safety above all.

In contrast, utilizing 100 percent of the runway length for a wet surface fails to account for the decreased performance, while using 110 percent or 120 percent may not correspond to standard safety recommendations for wet conditions specifically regarding turbojet aircraft. Thus, opting for 115 percent is a well-founded safety practice and aligns with recommended operational guidelines.