What does the B4 Full Data Block example UAL63 160 - 153 583 320 indicate?

The B4 Full Data Block example, indicated as UAL63 160 - 153 583 320, provides a detailed status of the aircraft, including its call sign (UAL63), altitude, groundspeed, and heading. The presence of "160 - 153" signifies that the aircraft’s Mode C transponder has reported an altitude of 160 (most likely in hundreds of feet) and a deviation to a lower altitude of 153, as they are sequentially listed.

This indicates that the aircraft has indeed deviated below its assigned altitude, which can potentially present safety concerns that air traffic controllers need to address promptly. The alert of such altitude deviation is crucial for controllers to take necessary action to ensure the safety of the air traffic and aid in the appropriate separation of aircraft.

Understanding this information is key for effective air traffic control since it provides immediate situational awareness about the aircraft's adherence to altitude assignments. Other possibilities such as communication loss, navigation issues, or being on a direct flight path do not align with the altitude reporting conveyed in the data block.