Cessna 550 flight crew reported a loss of Captain's primary flight instruments and uncontrollable elevator trim causing a loss of control. The Captain recovered the aircraft and landed safely using the co-pilots flight instruments.
Synopsis
Cessna 550 flight crew reported a loss of Captain's primary flight instruments and uncontrollable elevator trim causing a loss of control. The Captain recovered the aircraft and landed safely using the co-pilots flight instruments.
Narrative
I just wanted to tell what happen on my Citation flight from ZZZ2 to ZZZ1. The citation was an old 550 that's been modified so many times they can become dangerous. The flight took of and while I was in flight in IMC we started getting instrument errors with the attitude Gyro and the captain side started failing the auto pilot gets info from the flight director and kicked off and nose down effect happen. I immediately corrected everything and descended below RVSM to stay safe and gained control just to reset everything back up and I was going along fine and this time it happen again with runaway trim. I then pulled the circuit breakers to gain control and let ATC know what was going on as they were great to work with. Once I gained control back; I just hand flew the aircraft as the whole captains side instruments were basically out. I had vertical speed; and the HSI and the GPS. I had to then use the co pilots instruments till I landed. The issue we could when we landed was the operator installed a remote inverter switch on the co pilots arm rest in a bad position and it must have gotten hit and turned off. I didn't get any cass message or any light on the panel saying what was wrong. So hopefully the FAA might want to start limiting all these mods like this to keep stuff like this from happening again.
Second reporter narrative
While flying from ZZZ2 to ZZZ1 at 36000 ft. while in contact with ATC; the autopilot suddenly failed to maintain altitude. As the pilot not flying; I was covering the radio. I notified ATC and requested to leave RVSM airspace. We were cleared to 28000 ft. We stabilized the aircraft and continued at 28000 ft. to ensure safety. After transitioning to ZZZ; the PIC (Pilot in Command) attitude indicator tumbled. As we were troubleshooting; the autopilot suddenly began a rapid bank to the left and a diving attitude. With the PIC dealing with a tumbled gyro; I took the controls; depressed the autopilot disconnect; and held the disconnect depressed as if for run away trim. I then told the PIC to pull the pitch trim circuit breaker and notify ATC. We were cleared to 20000 ft. and ATC queried if we needed assistance. With the autopilot disabled and circuit breaker deactivating the trim I was able to manually fly the airplane. We continued our descent and upon passing 18000 ft. we entered VMC and I was able to continue manual control with visual flying to ZZZ1 with no further deviation or issue. The aircraft was turned over to maintenance.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.