Preliminary Report: CRJ experiences stabilizer trim problem

 - June 7, 2007, 10:22 AM

Bombardier CRJ, Milwaukee, Wis., April 1, 2007–Climbing out from General Mitchell International Airport (MKE) Runway 19R at 6:45 a.m., the Air Wisconsin CRJ, Flight 3714, experienced uncommanded nose-down stabilizer trim. The captain was flying. At 1,000 feet, the pilots retracted the flaps and disengaged the autopilot. The captain trimmed the airplane before completing the after-takeoff checklist, but the stabilizer trim continued to run and the aural alert sounded. The immediate action checklist was completed, as was the appropriate quick-reference handbook procedure.

The crew asked ATC for delay vectors and advised they might have to return to MKE for a precautionary landing. Moderate control pull forces were required to fly the aircraft at 10,000 feet and 250 knots. The crew used the acars system to calculate a weight-and-balance and redistributed the cabin load to ease control forces. They encountered ice at 10,000 feet, necessitating a descent to 8,000 feet. 

Having completed the checklist and declared an emergency, the crew selected 20 degrees of flap while between 8,000 and 6,000 feet and requested and received a 10- to 15-mile final approach to Runway 19R at MKE. The pilots said control forces were significantly lighter once the flaps were down, but more pull was required on the wheel once the gear was down. The landing was uneventful. After engine shutdown, the crew left the APU running and the airplane as configured for the landing, with all caution messages displayed.

Maintenance personnel downloaded the flight data recorder information, lubricated the trim switches and replaced the HSECU. The aircraft was released as airworthy and the crew flew it from MKE to PHL. The crew encountered no further problems.