A steering angle warning system comprising a rotation-measuring unit located on an aircraft, and an alarm unit. The rotation-measuring unit is arranged to output a first signal dependent on the steering angle between a nose landing gear of the aircraft and the longitudinal axis of the aircraft fuselage. The alarm unit is arranged to generate an alarm, in dependence on the first signal, when the steering angle is greater than a predetermined value, for example, 60 degrees. The rotation-measuring unit may also be arranged to perform a function in relation to an aircraft steering system, for example to indicate the steering angle to the pilot during ground manoeuvres.