hum: I disagree PBL. I would not assume that the port prop was feathered from the photo.
I am no accident investigator, but have briefly flown the Metroliner in a previous job. To me, the blade angles that can be guessed from looking at the photos seem consistent with normal engine/aircraft operation. The larger Metroliners like the Metro III and the even heavier Metro 23 (that we operated) suffer from a significant lack of control authority at low speeds. Below 120kt we often had to fight even the slightest deviations in roll and yaw with
full deflection of aileron and rudder - something that I have never encountered in any other aircraft type that I have flown before or thereafter. Especially asymmetric engine power at low speeds was extemely difficult to control.
Therefore, we were instructed during our type rating course to fly the aircraft as fast as possible for as long as possible (if runway length permitted of course) to maintain good control authority in every event. In practical terms, this was achieved by flying the approach fully configured not slower that 140kt until over the lights and bringing back the power to (flight) idle thereafter, which resulted in a touchdown speed of about 100kt. This procedure made sure that the time spent in the "difficult" speed range was reduced to a minimum (and with the engines at idle, there was no threat of asymmetric power).
Pulling back the throttles to idle in flight makes the governor sense an overspeed condition and move the blades to higher angles similar to the feathered position (for an overview of the system see here:
Articles). Oil pressure is required to move the propeller blades back to low angles, but unless power is reapplied, this does not happen.
So
if these pilots operated their Metroliner the same way we operated ours, the angle at which the propellers were left at the time of the accident
seems to me to be in accordance with normal operation.