From SIMHQ author Andy Bush:
http://www.simhq.com/simhq3/sims/air_combat/atgbasicsp3/atg3.shtmlDelivery Considerations Unique To Forward Firing Ordnance
We often think of these weapons as ‘point and shoot’ types. This ain’t necessarily so, as we will now see!!
The first consideration is a phenomenon known as ‘tip off.' Tip off applies only to rockets and is the result of the misalignment of the rocket launch line and the aircraft relative wind. Think of this misalignment as the angle of attack of the rocket when it comes out of the launcher. If the rocket is not pointed directly into the relative wind at launch, it will attempt to align itself with that wind as it is launched. This will happen because of the natural tendency of the rocket to streamline itself with the air flow of the relative wind. For this reason, fighter launcher rails are often designed to line up with the relative wind. This figure of an F-4 shows this.
Rockets are meant to be fired at or near one G conditions. Any G load (positive or negative) more than this one G firing condition will change the aircraft angle of attack, resulting in a rocket flight path that bends towards the relative wind. This ‘bending’ or change in the rocket flight path is the ‘tip off.' As the G load increases, so does the magnitude of the tip off. Here is a picture of tip off.
The only way to avoid tip off is to make very sure you are at approximately one G when firing your rockets. One final point...yawing your aircraft will produce a lateral or ‘sideways’ tip off. Do not use the rudder to correct your aim when shooting rockets!
The second consideration has to do with firing the gun while in a yaw (rudder deflected). While tip off is not a significant factor when firing the gun, the application of rudder to correct your aim point is. The gun is a wonderful thing but it is not a laser beam! The gun projectile still has to obey the laws of physics. One of these laws has to do with the resultant velocity vector of the projectile when it is fired.
The resultant velocity vector is a combination of the vector of the projectile and the velocity vector of the aircraft. The next figure shows the effect on the resultant bullet trajectory when the aircraft is yawed:
