Direct numerical simulations of the flow around an FFA-W3 series airfoil at a chord Reynolds number of 100,000 are performed to study the effects of rotation on flow over a section of a rotating wing. In order to achieve this goal, three simulations with different rotation speeds (and corresponding angles of attack) are carried out. Three additional simulations with the same angles of attack of the former but without including Coriolis and centrifugal forces are also computed. It is shown that rotation moves the transition location upstream on the suction side for low angles of attack, and on the pressure side, due to the enhancement of the shear-layer instability and its spanwise modulation. Nevertheless, rotation delays transition on the suction side for larger angles of attack. The reason for this change is most likely the fact that the shear-layer instability is much stronger in this case, and it is not bypassed by instabilities generated by rotation such as that from the inflectional spanwise velocity profiles. However, the latter can reduce the shear in the separation bubble, mitigating the rapid growth of the former. The onset of separation is not changed by rotation, but the trailing edge of the separation bubble is displaced downstream because of an enhanced reverse flow. The lift is only significantly affected by rotation when there are large separation regions on both suction and pressure surfaces, promoting its reduction.