The Outflow Ram Air Shield, normally closed, is driven open during the TO
roll, rotation & lading to deflect the airstream and create a low-pressure area over the Outflow Butterfly Valve.
The Butterfly Vlv controls the outflow of air at low flight altitudes.
The Thrust Recovery Vlv control air outflow at moderate to high flight altitudes.
[Edited 2005-01-21 20:34:04]