Are your back up systems really capable of back up?

A report of an incident in an aircraft which suffered a cabin depressurization in flight and had to make a rapid descent reinforces the need to ensure your back up systems are working and reliable. It appears that the flight was operating with a single compressor feeding both the cabin pressurisation systems. Due to the high demand, the air temperature and pressure were higher. However the aftercooler was not cooling the air sufficiently due to a cooler fan problem. This led to the compressor shutdown on high air temperature and subsequent loss of cabin pressure. Read the full incident in this link.