The UP2 valve is for aircraft where the doors remain closed when the gear is down, eg P51 Mustang.
Doors closed when gear down sequence. This air control valve replaces your standard unit and will not only control the retracts operation, but will control the opening/closing of the undercarriage doors.
When down is selected the valve will open the doors, then lower the retracts, the leg locks down and then the door closes. The opposite operation occurs when up is selected, all automatically.
Suits all retracts. Typically used on P-51 Mustangs.