Originally Posted by
hopp
The control lock allows minimal rudder movement. As you say, a control check would have discovered a lock. Also, the locking mechanism is quite visible, and locks the stick as well. That airframe can be taxied with minimal rudder input, by using brakes.
On the L-19 , the predecessor, taxiing requires a lot of brake inputs, due to small rudder size and a heavy tail.
Hard for me to believe an experienced tail wheel pilot would overlook the control lock skip the control check. Incapacitation seems more likely.
The pilot's radio transmissions indicate that he was alert when he was cleared and also a few seconds into the sequence. The controls surfaces are visible in the video and appear locked. The NTSB concluded that he could have completed the short taxi with the lock engaged. They also concluded the impact damage to the lock indicated that it was not stowed. The guy was a great pilot, he was also on the older side too.