[Steve]

Under actions, in an event, select Change AI (single or group depending on how you refer to your blackhawk [that is either by its group number or its ssn]). Then under the sub action, select combat speed. Set the combat speed to a low number (the speed that you want it to move at in km/hr. Click ok. Then do the exact same thing in a second event except change the Patrol Speed rather than the Combat speed. Set the Patrol speed to the same as the combat speed.

or you can do the same thing in a wac script with the following commands:
ssncspd(ssn,speed) set ssn to combat speed of #
ssnpspd(ssn,speed) set ssn to patrol speed of #




*credit for NovaLogic for info