What is used to recover aircraft that cannot make a normal arrested landing?

The correct choice is the barricade, which is specifically designed to recover aircraft that are unable to execute a normal arrested landing. A barricade is deployed as a last resort to stop an aircraft safely if its landing gear, brakes, or other critical systems have failed. It consists of a series of cables or nets that can effectively catch an aircraft, preventing it from overshooting the landing area and potentially causing damage or injury.

In contrast, a net barrier is a type of system used primarily on aircraft carriers to catch and safely decelerate a landing aircraft, but it is not typically the designated option for recovering aircraft in emergencies when normal landing patterns cannot be followed. The arrestor wire is a component typically used to catch and halt an aircraft during a normal landing, but it assumes that the aircraft can land on the landing gear, which does not apply when an aircraft cannot make a normal landing. A chase vehicle is used during recovery operations to assist or escort an aircraft but does not function as a mechanical recovery system for emergencies where normal landing procedures have failed.