I am looking at a diagram. The max nose wheel steering angle is 72 deg and effective steering angle is 66.1. My question is now why do we not have just one nose wheel steering angle? what is the difference between max nose wheel steering angle and effective steering angle ? And what angle is used for which cases?
When the two sides of the main landing gear move, each one tends to force a circle with its own radius and center, and is at the same time influenced by the nose landing gear own radius of turn.
Some tire sliding must occur due to the difference in circles, the actual center is between the three individual centers mentioned and the radius R3 is therefore a bit impacted.
Depending on the differential action on the brakes, and the use of engine thrust asymmetry, the result varies by a few percents (between types of turn 1 and 2 above).