Rockwell North American Civil Twin Jet
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Instrument
Flight Crew Last 90 Days 23; Flight Crew Total 4816; Flight Crew Type 2689
Situational Awareness
Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Human Factors
I had gone to the cabin to check on our elderly passenger who was traveling alone and has had 2 heart attacks and has a defib/pacemaker implant. While in the back; I noticed we were in a right banking turn so I immediately went back to the cockpit to see what was going on and noticed the autopilot disengaged light was illuminated and asked if we were being vectored. The copilot then realized that we were off course and in a gradual climb. I told him we needed to correct to which he [replied he] was already doing so and I overheard him tell Center that we were correcting. I hopped back in my seat; strapped in; and I took command. Upon discussing what happened; we agreed that if one of us is absent from the cockpit; the Pilot Flying (PF) is responsible for monitoring everything until the other pilot returns. The PF was apparently filling out the engine trend monitoring report and inadvertently tripped the autopilot.
Captain reported the First Officer (FO) allowed the aircraft to deviate from assigned altitude and track while he was out of the cockpit.