OverviewThe Carli Chassagne Couloir on the Aiguille du Midi is a moderate snow and ice route (can be some mixed climbing, depending on conditions) that tops out near the summit of the Aiguille du Midi. I climbed the route in late spring conditions (first week in June during a cold and snowy year.) I doubt that the route would retain enough snow/ice during the summer to make it worthwhile during the warmer months.
Getting ThereIt's most convenient to stay at the Plan de Aiguille hut, midway up the Aiguille du Midi. Wake up early, and from the hut, traverse under the North Face, following the route to the Grands Mulets hut. Pass the Mallory route, past a large ridge, and the next couloir is where this route starts. (This is also the start of the Eugster route.)
Route DescriptionClimb the first part of the Eugster couloir. At about 1/3 height, traverse sharply to the right, and get situated in a gully heading up, parallel to the Eugster route on your left. Follow the gully to its end at a rock band, then traverse left to rejoin the Eugster at the snowy exit slopes near the top of the North Face.
The lower sections of the route are relatively gentle, with the middle part of the climb presenting the most challenge, with some grade 3-4 ice (can be thin) or mixed climbing. Once out of the upper couloir, the rock climbing is pretty straight forward, and the very top of the route (after rejoining the Eugster) is a steep slog to the top.
Descent couldn't be easier: Take the tram back down to the valley.