Cessna 402/402C/B379 Businessliner/Utiliner
Flight Crew Air Transport Pilot (ATP)
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Excursion Runway
Human Factors; Weather
After the touchdown on the threshold; I continued to apply back pressure on the yoke until the nose wheel came to the ground and then I applied brakes with increasing pressure to test out the braking action of the runway. The aircraft decelerated normally; I would describe the braking as good to medium. We had slowed down to a slow taxi speed and by around Mid-field I increased power slightly to accelerate a small amount. As we approached the end of the runway at a normal taxi speed (just below a brisk walk) I applied brakes to make the turn and the brakes had zero impact on the speed or direction of the aircraft. I turned the rudders to try and make the turn and the direction of the aircraft was unaffected. I then announced to the first officer that we were likely to go off the end of the runway. I was on center line still and if we went off we would not hit the runway lights if I maintained center line. I stopped attempting to turn applied full aft yoke; full braking and ensured the throttles were at idle. The First Officer and I watched slowly as the aircraft departed the paved surface and stopped as soon as we were off the runway. I looked around there was a small snow pile a couple inches deep and we were on hard frozen ground. I then added power returned to the runway surface and taxied into the gate and stopped. Even though braking action was good on one part of the runway I should have not assumed braking action would be similar and proceeded with extra caution as I attempted to make the turn. I should have slowed down even more so as I approached the end of the runway. I also should not have taxi back onto the paved surface.
[Report narrative contained no additional information.]
C402 crew reported they departed the paved surface of the runway on rollout due to nil braking effectiveness.