Deviating from the assigned approach procedure.

Bottom line

Reprogramming tasks that occur unexpectedly can trigger pilot errors, which may result in flight path deviations or other undesired aircraft states. In the case of a radar vector to a final approach course or fix, a timed approach from a holding fix, or an approach for which the procedure specifies “No PT,” no pilot may make a procedure turn unless cleared to do so by ATC.