Any Unknown or Unlisted Aircraft Manufacturer
Flight Crew Private
Flight Crew Last 90 Days 0; Flight Crew Total 1000; Flight Crew Type 0
Situational Awareness; Human-Machine Interface; Time Pressure; Workload
Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Loss Of Aircraft Control
Flight Crew Became Reoriented; Flight Crew Took Evasive Action
Human Factors
Following a day flight; while flying as an observer pilot in a multi-engine prop aircraft.  After dropping their passenger off at ZZZ1 on the return leg Captain and First Officer were forced to make a weather diversion to ZZZ2.  They filled the aircraft with fuel and following hours of waiting were cleared to fly at night back to ZZZ.  Shortly after takeoff; Captain was adjusting his GPS across the cockpit in front of First Officer; during this short period he became disoriented in the clouds at night.  When both pilots peered back over at the steam gauges they were all spiraling; indicating a major problem.  As they broke out of the clouds they saw multiple lights in a line; ZZZ2 Approach began yelling at the aircraft asking if everything was OK; and the steam gauges continued spiraling.  After multiple quick scans and remembering his training; First Officer determined the lights were on the ground and they were in an inverted spiral.  First Officer took control of the aircraft and communications; rolled the aircraft upright and executed a four G pull to prevent both pilots' demise only about 200 ft. above the ground.  Conditions were night; IFR; low-light with a ceiling of 1200 ft. overcast.Captain was the pilot and aircraft owner based out of ZZZ.
Single Pilot Observer reported flying Pilot experienced a loss of aircraft control during level night IFR flight. Nonflying pilot took control of aircraft and rectified the inadvertent inverted spiral. Flight continued to base and landed safely.