BAe 125 Series 800
Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Troubleshooting; Workload
Aircraft Equipment Problem Critical
Flight Crew FLC Overrode Automation; Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Maintenance Action
Aircraft
All preflight control checks were normal. First flight checks including Rudder Bias system checked normal. After takeoff still hand flying aircraft and was given a climbing left turn. As I initiated it at about 800 FT and applied left rudder to keep coordinated flight; I felt enormous pressure. SIC had engaged YD. I rolled out of turn on assigned heading and disengaged YD. Pressure/resistance was still felt on rudder pedals. Speed was approximately 200 KTS. It took a huge amount of force to displace rudder pedals. Felt like the Rudder Bias system had 'engaged' itself simultaneously on BOTH sides. No abnormal indications on MWS either. We requested return to the departure airport and landed. Adjusting speed for landing had no effect on pedal pressure. After landing and thrust at idle pedals checked normal free and clear. Advancing thrust to higher power setting again got the resistance again.
The reporter explained the BAe 125 Series 800 engines high pressure bleed pressurizes Rudder Bias pistons one on each side of the rudder; so that if an engine fails the high pressure bleed from the operating engine introduces some rudder to counteract the loss of thrust yaw. The pilot then adds additional rudder as needed. In this case; the rudder restriction may indicate high pressure bleed is activating both Rudder Bias pistons simultaneously restricting rudder movement equally in either direction; in other words locked. During preflight the rudder 'kick' was felt and in this instance; after landing idle thrust unlocked the rudder. When thrust increased during post landing engine run up; the rudder pedals lock again. This anomaly is a repeat issue for this aircraft.
A pilot reported his BAe 125 Series 800 rudder pedals became very difficult to displace during climbout as if the Rudder Bias system had self-engaged; so the crew returned to the departure airport where the rudder pedals released with the thrust levers at idle.