On departure for the night air taxi cargo flight, the flight crew experienced a problem with the crew intercom system. The crew initiated their descent at a 'later than normal distance' from the airport, and as a result, a power reduction below 25 percent torque was required, which set off the gear warning horn. The sound 'eventually became part of the background noise.' During the approach, the captain asked the tower to dim the runway lights. At that time, the runway and approach lights went out and the crew lost sight of the runway. While the captain was asking the tower to turn the lights back on, the first officer called 'gear down, syncs off, speeds high, below the line check list.' The captain did not hear the first officer's callout and did not lower the landing gear. The captain stated that he did not hear the first officer's callout 'either because of the conversation [he] was having with the tower or because of the intercom system difficulties.' As the approach continued, the first officer had a problem slowing the airplane to proper approach speed. The airplane touched down on the runway with the landing gear retracted, 'slid' about 2,500 feet and exited the left side of the runway.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows: