SA-227 AC Metro III
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Situational Awareness
Aircraft Equipment Problem Less Severe; Ground Event / Encounter Object; Ground Excursion Taxiway
Aircraft Aircraft Damaged
Aircraft; Human Factors
I made a normal landing; cleared [on a forward high speed turnoff]. About 200 yards prior to the high speed; moved power levers to low; continued onto the high speed doing about 40 to 50 knots. Slowing down for [sharp] turn back up [the parallel] taxiway plane made a very wide turn. I had full LH rudder and I was holding the park button but aircraft continued to make wide turn. Got on brakes checked E1 speed lever full back and nose steering lite on; aircraft still going wide. As I got plane stopped I was off the taxiway with RH side of aircraft and hit one of the lights. I was off the west side of the taxiway heading south. There is about 25 feet of additional pavement past the lights but I was over the edge taxi line. I knew I had hit something with either the prop or landing gear on the right hand side of aircraft. I continued to taxi and heard a noise from the prop and immediately feathered the engine. The engine was in BETA range at time of incident and immediately shut down to avoid any additional damage. I taxied in on one engine it was a little difficult with one engine. A combination of extra speed on the high speed and the lack of the nose wheel park button working as well as it should and just the normal nose wheel capability not being there exacerbated the problem. I have made [this high speed] many times and never had to use the park button to clear and get on the parallel taxiway.  The park button has been slow to give additional degrees of travel during my previous flights but did not work well when I taxied off. It was daytime the taxi lights were off and I did not realize I was that close to them as I tried to stop. I immediately told ground control I thought I had hit one of the taxi lights on the west side of [the taxiway] just south of [the high speed]. Aircraft weight was 11;000 at landing; landed with full flaps. Just take taxiway slower in case steering does not work as well as it should.
SA227 Captain reported a taxiway excursion after exiting the landing runway on a high speed taxiway. The park button had no apparent effect on the nose wheel steering angle. The right propeller struck a taxiway light and the engine was shut down for taxi in.