This is a controversial topic. Some naturally curly haired experts believe that the natural curl profile should be honored at all times which means bangs should not be cut into the natural hairline. Other curl experts believe bangs (fringes) can be carefully chiseled into a head of natural curls as long as the bangs are cut very long to allow for natural curl shrinkage.
Hairstylists who understand how to work with naturally curly hair suggest that the shorted the bang hair should be on natural curls is chin length. Some suggest that bangs should even be shoulder length to allow for the bangs to form into loose ringlets which merge into the entire natural curl profile.
Curly hair can shrink as much as 4-6 inches in length when it dries after being wet for cutting. Always make allowances for curl shrinkage when bangs are cut to avoid haivng short puffs of curls at the forehead instead of long bangs.
Although some people with natural curls may try to wear their bangs shorter and temporarily straightened by means of relaxers, straighteners or similar, this is not considered the best hairstyle design for natural curly hair by many curl experts.