NTSB Factual Report

The pilot reported that during the landing roll, as the tailwheel lowered, the airplane began to veer to the left. He applied full right rudder, and right brake, with no effect. The pilot stated that he increased the throttle on the left engine, but by that time, the aircraft had veered partially off the runway to the left and struck an airport sign. The airplane sustained substantial damage to the left wing and fuselage.

The pilot reported there were no pre-impact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation

NTSB Probable Cause

The pilot's failure to maintain directional control, which resulted in a runway excursion, and a collision with a sign.