This is a nice couloir-climb on the far left side of the Triangle du Tacul. In fact, it is in between the hanging icefield and the the rocky Triangle.
The route was first climbed by P. Labrume, J. Martin, M. Negri, together with A. Contamine on the fifth of august, 1962.
The first winter-ascent was done by E. Barbeto, M. Barbeto, A. Bonomi and L. Ratto on the twelfth of february 1967.
The height of the couloir is 350 m. and the average angle is about 50 degrees.
You reach the start of the route from the Cosmiques hut or the Biv. Abri Simond in 1/2 hour by a walkl across the Vallee Blanche or from the Aiguille du Midi in 1 hour via the Col du Midi and the Vallee Blanche.
You can also reach the route from the Torino hut, but this will add at least an hour to your approach.
Go to the far left of the Triangle du Tacul and climb up the 40 degree snow-slope. Make sure to stay on the right side of the hanging glacier.
The angle steepens and you enter the couloir. This is a very nice part of the route, with on your left hand a (near) vertical icewall. The couloir gets narrower. Climb straight up the couloir for until you reach the north rigde above the Triangle du Tacul.
From here you can follow the ridge to the summit of Mont Blanc du Tacul in 1 hour or traverse up and right and descent the normal route (NW-Flank)
The time I climbed it, the route to the summit was too dangeres because of instable snow, the normal route was too dangerous because of on instable serac. So we rapelled down the Triangle and finished at the start of the Contamine-Mazeaud
Just remember that the normal route can be very dangerous. This is especially the case when there is fresh snow. This face is very prone to avalanches!
The gear to bring is the usual ice-climbing gear. So bring sharp crampons and axes, several icescrews, quickdraws, slings, a threader and a rope.