Impeller containment system

An aircraft engine, comprising:

• an air inlet;
• a compressor section for receiving air from the air inlet, the compressor section having a centrifugal impeller mounted for rotation about an axis and an outer shroud, the centrifugal impeller including an impeller hub, the outer shroud extending radially outwardly of the impeller hub to define an annular flow path radially between the impeller hub and the outer shroud, the outer shroud at least in part surrounding the impeller hub, and blades extending radially outwardly from the impeller hub and operable to rotate within the annular flow path;
• and
• an air inlet case having a radially outer wall extending from the air inlet to the outer shroud and a radially inner wall extending from the air inlet to the impeller hub, an annular passage defined radially between the radially outer wall and the radially inner wall fluidly coupling the air inlet to the centrifugal impeller, the radially outer wall including a frangible element adjacent a junction between the radially outer wall and the outer shroud, the frangible element extending about an outer circumference of the radially outer wall and frangibly connecting the radially outer wall to the outer shroud.