Light Transport; Low Wing; 2 Turboprop Eng
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 100; Flight Crew Total 5700; Flight Crew Type 520
Communication Breakdown; Confusion; Human-Machine Interface
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented
Human Factors; Procedure
Acting captain; flying pilot; during company line-check; observed the non-flying pilot experiencing difficulties checking in with Cleveland Center (ZOB) after receiving a hand-off from Toledo Departure Control.  After the air traffic controller called the aircraft twice; the controller called a third time and stated that if the aircraft could hear the controller to contact them on an alternate frequency.  I noticed the non-flying pilot was not reacting/responding to the radio call and I could not directly communicate with the non-flying pilot over the crew intercom system; so I changed the radio frequency and checked in with Cleveland Center (ZOB).The non-flying pilot observed the radio frequency change; confused with the change; and returned the radio to the original frequency. Flying and Non-Flying Pilots quickly identified that the 'Crew Intercom' activation switch had been deactivated; and regained crew communication.Flying pilot became alarmed when his radio began receiving the KTOL ATIS; and became more actively involved with understanding the status of the radio settings.  During this time; the non-flying pilot was checking in with Cleveland Center.It took additional time for the crew to identify that the 'Split Mode' switch was activated; causing the pilot and co-pilot to be transmitting/receiving independently on two different communication radios (tuned to two different frequencies).  If the flying pilot selected COM-1; the non-flying pilot radio automatically changed to COM-2.  When the non-flying pilot reselected COM-1; the flying pilot automatically/involuntarily changed back to COM-2.There was a short period of time where the each pilot was alternating to COM-1 (Cleveland Center; while the other pilot was on a different radio/frequency) and subsequently communicating with the Cleveland Center as that controller was actively trying to understand why two distinctively different voices (pilot & copilot) was responding as the same aircraft.After the 'Split Mode' switched was resolved; and both pilots were concurrently on Com-1; the flying-pilot relinquished all radio communications back to the non-flying pilot.
An air taxi Captain reported that the flight crew had difficulty in managing the radio panel.