Flow deflecting devices

A translating cowl thrust reverser for a ducted fan gas turbine engine comprising radially inner and outer walls defining a fan duct, means for translating a portion of the radially outer wall axially to open up in the radially outer wall an aperture which has an inlet communicating with the fan duct and an outlet communicating with atmosphere, means for simultaneously blocking the fan duct as the aperture is opened and for directing flow from the fan duct into the inlet of the aperture, the aperture having upstream and downstream side-walls which are shaped to give the flow through the aperture a forward component of velocity from the outlet thereof, and a substantially axially extending at least part-annular plate extending in a downstream direction from the upstream side-wall of the aperture only into a turbulent region of the flow and terminating upstream of the downstream extent of the upstream side-wall and defining with the upstream side-wall an annular recess open to the flow and in which, in operation, the flow causes a reduced pressure to delay the onset of separation from the upstream side-wall.