Date: 201705
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: Gulfstream G200 (IAI 1126 Galaxy)
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class E ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Rudder Trim System
Component problem: Malfunctioning
Reporter organization: Air Taxi
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Troubleshooting; Distraction
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Critical; Inflight Event / Encounter Loss Of Aircraft Control
Detector: Person Flight Crew
When detected: In-flight
Result: Aircraft Automation Overrode Flight Crew; Flight Crew Took Evasive Action; Flight Crew Overcame Equipment Problem; Flight Crew Regained Aircraft Control; General Maintenance Action
Contributing factors: Aircraft; Company Policy
Primary problem: Aircraft

Narrative: Prior to takeoff; cockpit checks were completed and the rudder trim was actuated full deflection left and right per the checklist and no defects were discovered. After takeoff I adjusted the rudder trim slightly right. At this time the rudder trim selector knob pulled off of the rudder trim post. Assuming that the setscrew only backed out we placed the knob back on the post and continued the flight under normal operations. Once at an altitude of 10;000 feet; we briefed that we would not touch the rudder trim and leave it in the set position for the remainder of the flight.Approach cleared us direct an arrival waypoint and to cross at 8;000 feet. In the descent though 15;000 feet; out of habit I attempted to apply the slightest amount of right rudder trim to true the aircraft. At this time the rudder trim abruptly applied full uncommanded deflection to the right. Which was indicated on the primary EICAS page of nine full units right trim. Causing a severe skid at an indicated airspeed around 300 kts. The autopilot was immediately disconnected in efforts to regain control of the aircraft. At this time I was applying left rudder as hard as possible and asked for the pilot not flying to add rudder input as well in attempt to remove the airplane from the skid. During the skid the cabin host was walking up the main entry door to open the curtain. At which time cabin host was promptly commanded to take a seat. The non-flying pilot attempted to re-center the rudder trim using the unsecured trim knob. However; due to the knob not being attached pilot not flying was unable to move the rudder trim. At this time I notified ATC that we were having a problem with the rudder trim; we were off course and unable to make the crossing restriction. ATC cleared us direct to the airport and to maintain 6;000 feet. I called for the rudder trim circuit breakers to be pulled in an effort to de-energize the trim motor. After the PNF was able to find an on board multi-tool that we keep in the cockpit; PNF was able to latch onto the trim post. When we realized this we pushed the CB's back in and attempted to re-center the rudder trim. The PNF discovered that the switch was not self-centering and that after moving the trim to the left PNF would have to move it back to the right to stop the movement of the motor. At which time I called for the CB's to be pulled again to ensure that the trim motor would not activate. During the skid fuel migrated to the left wing causing an imbalance between 300-400 lbs. After regaining control of the aircraft I asked ATC to provide either delaying vectors or a hold. ATC cleared us for a present position hold at 6;000 feet and the autopilot was re-engaged in the holding pattern. I attempted to contact maintenance control by the use of the satellite phone to inquire if they would prefer for us to land at a nearby airport. However; due to the company's automated answering service we were unable to make contact with company. At this point I made the decision to continue to the original planned airport of arrival. After being cleared direct for the airport by ATC we were able rebalance the fuel and made a successful landing. After arrival a post flight inspection found no visible structural damage and no injuries were reported. After debriefing with the crew I made the decision that we were finished for the night as nerves were a bit shaken. Provide a discrete phone number for flights crews to be able to contact company without having to use the automated answering service.


Second narrative: Enroute the PF tried to adjust rudder trim for a more coordinated flight; the rudder trim knob became dislodged from the rudder trim post. After a short discussion between the PF; and myself we decided to not make any more rudder trim corrections for the remainder of the flight and determined that it was logical to continue the flight. While in descent into our filed destination; I advised the PF that I was going to be 'offline' to obtain the current weather and notify the FBO of our arrival. While 'offline' I felt a sudden and rapid yaw from the airplane. It was at this time that I knew there was a problem. The PF immediately disconnected the autopilot as PF gained control of the airplane. At this point; I had noticed that PF's hand was on or around the rudder trim tab. With my head down in the cockpit I knew that the Rudder Trim Tab Knob had become dislodged with the rudder trim post. I grabbed for the trim tab knob and tried to get it to sit back down on the post but because of the yawing and uncontrolled flight profile; I was unable to do so. During this time I was instructed by the PF to disconnect the Rudder Trim circuit breakers; which I did. Returning to the task of correcting the rudder trim problem; I decided to abandon the knob and reach for a small Leatherman multi-tool that was in the cockpit when it was decided that the multi-tool was our best option for repair. The PF then instructed me to reconnect the circuit breakers to allow movement of the rudder trim motor; which I did. Using the multi-tool; I was able to turn the rudder trim post to the left to gain a more coordinated flight. While doing this; we both noticed that the rudder trim continued to travel in the opposite direction and the auto stop was not working; leaving me to try to find 'center' and stop it there. After several attempts to gain positive control; we were successful. Once again; the PF instructed me to pull the rudder trim circuit breakers; which I did. We gained positive control of the aircraft and were able to re-engage the autopilot. It was at this time that I was able to come back 'online' and able to hear all communications with ATC. I was given positive control of the aircraft by the PF as he contacted ATC and asked for a hold to try to contact Maintenance Control. We were unable to make contact; and decided that we would continue on to our original destination. We landed without incident and taxied to our FBO.


Synopsis: G200 flight crew experienced a rudder hard-over after a rudder trim adjustment during which the rudder trim knob detached from the post. The crew was able to center the rudder trim using a Leatherman multi-tool then pulled the circuit breaker to prevent further movement.