Grand Theft Auto: San Andreas Question
To fly forwards whit a helicopter,you must make the helicopter decline a little down front,and acelerate too,and then the helicopter willl move forwards.
Straight forward answer: By default it's "W" + "up arrow."
And to do any maneuvering, use the other arrows, as well as the WASD... This could all of course, be seen in the vehicle controls, but I had trouble figuring it out too.
Walkthroughs & FAQs
GTA: San Andreas Navigation