P180 Avanti
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 60; Flight Crew Total 3000; Flight Crew Type 375
Training / Qualification; Confusion; Human-Machine Interface; Situational Awareness
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Excursion Taxiway
Flight Crew Took Evasive Action
Aircraft; Chart Or Publication; Human Factors
After an uneventful flight; we landed on Runway 12R and cleared the runway to the right. Given taxi instructions by Ground to cross the next perpendicular taxiway and turn right on the next one to the FBO. As we turned right onto the taxiway; I (pilot not flying) then ran the after landing checklist. We were advised of conflicting traffic departing the ramp; a King Air and helicopter. Neither one was a factor for us. As we approached the left turn into the ramp; our steering and brakes (both hydraulically actuated with a pump) did not work. The Captain tried to turn and slow the plane but it continued forward. I tried my brakes and; upon learning that they did not work; I immediately grabbed the condition levers and pulled them back to cutoff. Additionally I turned off the fuel shutoff valves. We rolled from the taxiway at a VERY slow rate of speed into the grass. The grass was dry and on the same level as the taxiway and there was no drop off from the edge of the taxiway. The speed was a slow walk and very gentle. Upon coming to a stop we put on the parking brake and finished securing the aircraft. There was no damage to the airplane or airport property. We were pulled out of the grass by the FBO. Upon further inspection; we confirmed that there was no damage to airport property or the airplane. We later determined that the Captain; the pilot flying; had inadvertently turned off the right bleed and hydraulic switch instead of the left and right bleeds. All three switches are identical and on the same level; right next to each other. Pilot flying will now ONLY worry about taxiing. He will call for all switches to be turned off by the pilot not flying.
A P180's left and right engine bleed are identical and located next to the Hydraulic switch; so a Captain closed a bleed and turned off the hydraulics which caused a loss of steering and brakes followed by a taxiway excursion as the aircraft came to a stop undamaged.