Classic CFIT

So what exactly happened?  What we know about the accident is consistent with "controlled flight into terrain."  Opting out of the instrument flight system, the pilot had to stay under the clouds.  He couldn't go through them because once inside, he wouldn't be able to see and might bump into something hard and pointy.  So he had to stay in the clear and visually pick his way around the terrain in his path.  But as he maneuvered under the low clouds and around the fog, he suddenly came upon a mountain's steep up-slope.  He shoved the throttle forward, pulled the nose up and began a climb.  But the terrain rose faster than could his aircraft.  He bellied onto the rising slope while in full control of a perfectly functioning aircraft.
At least that how it looks.
According to John Bouker, the pilot who found the wreck:

The Otter had plowed into the hill. He bounced up the mountain. He looked like he was in a full-power climb. . the plane appeared mostly intact.

That’s a classic "controlled flight into terrain” scenario.

 

 

REFERENCE

 

Pilot in Senator Stevens Crash a Hero? : Aviation Law Monitor. (n.d.). Retrieved from http://www.aviationlawmonitor.com/2010/08/articles/accident-investigation-1/pilot-in-senator-stevens-crash-a-hero/