If not approved, placing power levers below flight idle on a turboprop can be very dangerous. The F50 has a different propeller(Dowty) for its PW100 engine but as this accident report shows, the three second time period that it was done on this aircraft was fatal. Do a 360(or some other safe manouver) if you are too high.
http://www.skybrary.aero/bookshelf/books/677.pdf