Which group in the ADG classification has a tail height of less than 20 feet?

ADG Group I is characterized by aircraft that have a tail height of less than 20 feet. This group includes smaller general aviation and commuter aircraft, which typically require less space for operations and maneuvers on the airport ground. Understanding the tail height of different aircraft groups is crucial for airport operations, as it influences the design of taxiways, runways, and other airport infrastructure. In contrast, the other groups, which include larger commercial and transport aircraft, feature tail heights that exceed 20 feet, thus necessitating different considerations for ground handling, clearance, and operations within the airport environment. This classification plays a significant role in ensuring safety and efficiency in airport design and operations, particularly regarding the spatial requirements for different aircraft types.