Aux Air Doors
The Aux Air Doors, upper and lower, were open at lower speeds, and were used in conjunction with an annular ring type valve which surrounded the intake duct, just in front of the engine. They closed automatically at, if I remember correctly, 240 kts. I seem to remember that the flaps would retract automatically at this speed too, if they had been forgotten by the pilot! But it is a long time ago, I left 43 in Nov '84!