Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Aircraft Equipment Problem Critical
Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft
ZZZ to ZZZ1; visual approach into Runway XX; VMC weather conditions. At approximately 300 feet AGL two messages populated on the EICAS; PTRIM (Pitch Trim) MAIN INOP and PTRIM BACKUP INOP. Both crew members initially looked to see if half of the trim control on either side yolk had been accidentally held; which would cause the effected main control to become INOP; neither side was observed being pressed or stuck. The crew then quickly tested each main control and back up control; one at a time; each control switch failed to activate/ control the elevator trim. The airspeed was 145 KTS IAS. The crew briefed that the controls were trimmed for landing speed; 145 KTS; and due to the short final; now near 200 feet AGL; the landing would be continued. The crew also quickly briefed that in the event of a go-around special attention would need to be paid attention to airspeed due to the INOP trim and the traffic pattern and second landing would be flown at/near 145 KTS. The flight terminated safely and maintenance was called. Maintenance investigation found that when the autopilot disconnect button was pressed to disengage the autopilot it became stuck in the pressed position. This stuck position lead to the dual; main and backup; trim inoperative condition.I would very much like to know if this is a replicable condition with the AP disconnect button or if this failure was an anomaly. If this is a programming fail safe designed into the system; then awareness training might be beneficial to the rest of the group.
Air carrier Captain reported PITCH TRIM FAIL EICAS messages during short final approach.