Technician reported referencing the aircraft Log; the aircraft experienced cabin depressurization during flight. Technicians found the right-side pack duct had blown off from the bypass valve.

Narrative

Aircraft X was in route from ZZZ1 to ZZZ2 on Day 0. While in flight at 36;000 feet the aircraft experienced a cabin depressurization and performed an immediate descent and landed in ZZZ. The left pack was on MEL and the aircraft was operating on the right pack only. I was one of the 3 technicians dispatched to ZZZ out of ZZZ3 to troubleshoot and repair the aircraft. It was found that a duct on the operating pack had blown off from a bypass valve with enough force to damage the inside of the pack bay body fairing panel. The design of this duct is such that one V-band clamp at the top is the only thing securing it in place. If that clamp fails; loosens; or wears for any reason; then the duct will simply rotate and come off of the bypass valve. Reference aircraft IPC XX-XX-XX-XXX. This clamp holding the duct was found loose enough that this is what happened causing the duct to rotate and come off in flight; causing the cabin pressure to drop. I find it hard to believe that this is an approved design on an aircraft. There is nothing to prevent the duct from doing this and is obviously very important to maintaining cabin pressure. I believe that this is a poor design and may happen again.