Winter Variation

Winter Variation, abbreviated as WV, sometimes referred to as F2LL, is a subset of VLS used for orienting the last layer corners during insertion of the final F2L slot. It is generally used in conjunction with methods in which the last layer edges are already oriented before insertion of the final F2L block, such as ZZ or Petrus.
WV may only be used in last slot cases where the final corneredge pair are already connected in the ULayer. In the R U R' case Summer Variation can be applied. After using WV, all the pieces will be correctly oriented in the last layer, and the solver must use PLL algorithms to correctly position them.
There are 27 Winter Variation algorithms total, one for each configuration of corner orientations. WV cases are set up so there is a corneredge pair in the top layer to be placed in the final slot. Recognition of cases is typically done by looking at 3 of the corners in the top layer (the last corner's orientation is always dependent on the other 3). Since the last slot can potentially be in 1 of 4 positions, the solver must readily be able to recognize mirror cases and apply mirror algorithms in order to use WV.
The benefit to learning WV is that the solver uses fewer moves than directly placing the final c/e pair and using standard OCLL algorithms. The average move count for optimal WV algorithms is 8.07. In addition, PLL algorithms are generally well known, since PLL is the last step of the popular Fridrich method.
The original description and rationale for this variation can be seen in the yahoo speedsolvingrubikscube group here.
See also
External links
 A variation on the Petrus Method  initial proposal of the method
 Sebastien Felix's WV Page
 Jack Eisenmann's WV Page
 Dragon Cube WV Page
 YouTube: F2LL Winter Variation
 Speedsolving.com: F2LL winter variation, is it worth learning?
 Speedcubingtips.eu Winter Variation algs