Question about rotation.

I have been doing a few projects that require a lot of rotation (mainly animation, but this isn’t about that). The problem is that once the object is rotate to a specific degree, and another type of rotation needs to be preformed, with just “R” it would require manipulation of multiple axis. My question is:
Is there a way to rotate an object on a relative axis?
For example, you have an aircraft, if you rotate it on it’s Z axis 45 degrees, and want to then change it’s pitch, how would you do that by only rotating on the Y axis for the object?
Also, Is there a way to add a rotation constraint? such as, this object can only rotate on it’s X axis. Any help is appreciated, thanks.

Select the object andpress ‘r’ twice to activate the trackball mode. Then you can enter a number to rotate the object around the horizontal axis (according to the viewpoint) then press tab to enter a number for the vertical axis (again according to the viewpoint).

I’m a newbie too … but my suggestion would be to use the “Transform Manipulator” and switch it to “Local” mode from “Global” mode. I don’t think one can use the “R” key but the visual transform manipulator now provides x,y,z rotations that are relative to the object and not global to the scene.

Another tip. You can use the view coordinates: align the view (edit mode:Shift+V, object mode:*) then rotate it with numpad keys and press R. You can set the view rotation steps in User Preferences.

that will not work, there is no way that i will be able to line up the viewpoint to be parallel with the an axis of the object, 45 degrees is one thing, but what if it’s something like 23.841 degrees, if it’s not perfect it will not rotate correctly. I’m looking more of something like, you parent it to an empty, and it rotates on the empties axis, is there a way to do that?

You kinda answered your own question, just parent the object to an empty. To do so select the object, then the empty and press Ctrl + P

If i parent it to the empty, then select the object and hit “R” then “Y” will it rotate on the global Y, or the empties Y?

R rotates relative to the Global Axii (Center of the Scene or any other Pivot Point selected in the Pivot menu icon in the header), RR rotates relative to the Local Axii (Object Center or any other Pivot). You can lock an axis in the Transform Properties tab (N).