Why did my Chiffon Cake collapse?
Chiffon cake, like it's cousin angel food cake, is mostly air. A big pile of protein bubbles stiffened with a little starch.

One very important step is not reflected in your recipe:  

When the cake is completely baked the proteins have set and the starches have gelatinized but the starches are still very soft. The cake won't have its firm structure until the starches have been able to cool and set.

All recipes call for inverting the cake immediately when it comes out of the oven. The cake is allowed to cool, inverted and still in the pan, for a good hour to ensure the starches have set.

Special pans with legs or a long tube center are used for this:  



Notice that in addition to the feet that it is a tube pan. This is important because the interior of these cakes is very insulated and won't be able to cook completely before the outside is overcooked.

When my angel food cake pans were packed I had good success using a pot with a mason jar in the middle. I was surprised it came out perfectly.

TL;DR -
Use a cake pan with a tube,
Invert the cake right when it comes out of the oven and let it cool completely.

*Note
Catija is correct that these amounts look way too small for a full cake. If you are trying to bake that in a full sized cake pan it could possibly be over rising and not have enough structure to support itself when it comes out.