ᴱQ. initial and intervocalic [xʷ] became [f]; [xʷ-|VxʷV] > [f-|VfV]
References ✧ PE12/17-18
Order (01300)
| After | 01200 | [xʷu] became [xu] | ||
| Before | 02000 | intervocalic voiceless spirants became voiced | 
Phonetic Rule Elements
|  | > |  | ✧ PE12/17 (x͡w > f) | 
|  | > |  | ✧ PE12/17 (x͡w > f; between vowels) | 
Phonetic Rule Examples
| xʷeno > feno | xʷ- > f- | ᴱ√HEN+U > ᴱQ. feno | ✧ QL/38 | 
| xʷex > fex | xʷ- > f- | ᴱ√ǶEHE > ᴱQ. Fé | ✧ QL/41 |