Falcon 50
Flight Crew Air Transport Pilot (ATP)
Workload; Troubleshooting; Fatigue; Distraction; Confusion
Aircraft Equipment Problem Less Severe; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action; General Maintenance Action
Aircraft
This was an FAR 91 leg returning from an FAR 135 trip. Shortly after departure talking to Departure we were given a climb to 11;000. I had been in the process of completing the After Takeoff Checklist when the pilot flying disconnected the AP and pushed the airplane over to recapture the assigned altitude. I noted our altitude was 11;800. Immediately after the pilot flying disconnected the autopilot; two warning messages illuminated. They were autopilot TRIM; and MISTRIM. In the DA-50 when electric trim fails; the autopilot does not have pitch authority. However; it does not disconnect the autopilot. Therefore the autopilot tried to capture the altitude but was unable. We returned to altitude and continued our flight. ATC did not make any reference to our altitude. As we proceeded to our filed destination we continued troubleshooting the electric trim. It seemed to be operating at 1/2 speed if at all. We tried the autopilot one more time and after a brief period of time it was apparent it would not hold altitude. The trim was written up and Maintenance was notified. As a possible contributing factor; the morning of the day before this trip we were assigned by 'hot standby.' We were required to sit at the airport for six hours with the APU running which means we had to be awake and ready to fly. I believe this contributed to our alertness. Even under a maintenance situation; pilot awareness is primarily. We should have noticed the altitude earlier. Departure is a busy phase of flight; heightened alertness is important.
This occurrence serves as a good reminder for all first officers who are building left seat pilot flying experience; where their focus and attention should be as the pilot flying and to resist the urge to perform pilot not flying duties that they may be accustomed to performing. This is also a good example of how quickly the links of 'The Chain' can build.
A DA-50 annunciated TRIM and MISTRIM while climbing to 11;000 FT and so the autopilot did not automatically capture the altitude; but overshot by 800 FT. Fatigue; task saturation and inexperience well elements in this event.