Super King Air 350
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Flight Engineer; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 250; Flight Crew Total 24500; Flight Crew Type 500
Distraction
Ground Excursion Taxiway
Flight Crew Became Reoriented
Aircraft; Human Factors
Even though our aircraft is a FAA certificated single pilot airplane; for operational and insurance reasons we operate with a copilot. On this day; the co pilot was fresh out of orientation and currency flights; so it was an 'OE' flight. We took things slow; had him load the FMC before taxiing from the ramp. As is our practice; we had received our clearance prior to taxi; so we had our cleared ATC route written down. It was different than filed; but the co pilot had been the one to receive the clearance and had a 3 digit identifier written down for our first fix - I had verified what was written down; and it looked correct. At the end of the runway I parked in the run up block and set the brakes to run through the pre take off checklist - challenge/response as is our practice with a two pilot operation. Upon review of the FMC programming; I discovered that the first fix the new co pilot had inserted was not what he had written down; and the course was 90 degrees off. A training session ensued. During this training session; the brakes released. I had had this happen in the past; especially if the brakes were not adequately 'pumped' after pulling the parking brake handle. Today; I did not catch it until the nose was off the hard surface of the run up pad. We were perhaps 3 feet into the grass and no damage was done. I shut down the engines and called for a tug to push us back onto the pavement. In my opinion; factors are: 1) Poor brakes (design from the factory - we intend to purchase after market brakes once the Company can jump through all of the required FAA hoops for an STC.) 2) Training in progress - it would cost our company thousands of dollars to purchase a PC based trainer for this particular FMC; and they are not inclined to pay for either the program OR simulator training for co pilots. 3) My diversion of attention and desire to create a synergistic environment - encouraging the (insurance required) co pilot to actually be a part of the flight. A less costly PC trainer for industry avionics would have helped. We could do more familiarization on the FMC prior to 'OE'. Another option would have been to take the operation out of a crew concept and do everything myself.
King air Captain reports a taxiway excursion due to a parking brake failure while discussing FMC programing with a new Copilot in the runup area.