The 51st Hoverbourne were deployed in Mega-City One during the Chaos Day riots to assist judges. Normally, MC-1 military forces are not used for such operations but were called in out of desperation as the judges were overwhelmed.
A "six pack" of soldiers and two Meks were given to Judge Dredd to help retake San Wannamaker Block, which was compromised by the bug and whose Citi-Def forces were split between loyalists and infected mutineers. Dredd sent the six pack and one Mek with Judge Beeny to assault from the upper levels while he took the other Mek and three auxiliaries to assault from the ground floor. The six pack and Meks provided support as they cleared out all infected and rebellious citizens and citi-def. 
The 51st Hoverbourne is likely the equivalent of an airbourne division, but can be deployed from hovercraft rather than planes or helicopter. They utilize Meks (large bipedal assault droids), and carry rifles similar to those used by Citi-Def. They do not appear to be judges, based on their lack of related insignia, or members of the Space Corps, suggesting that they are based on Earth. The soldiers seen in the Day of Chaos riots wore armor over loose fatigues, helmets, and gas masks.
- ↑ Day of Chaos: Endgame