Abstract: An intake (12) for a gas turbine engine (10) has an annular lip structure (23) extending about a central axis (11) and defining an intake opening. The annular lip structure (23) has a leading edge (38) located between a radially inwardly facing portion of the intake and a radially outwardly facing portion of the intake (12). The annular lip structure (23) has upper, lower and opposing side regions on either side of the central axis (11). The annular lip structure (23) comprises a formation (40; 42; 48) on the radially inwardly facing portion arranged to create a non-symmetric flow field over the opposing side regions of the annular lip structure (23). The formation (40; 42; 48) may be actively controlled in response to ground vortex conditions.