Incident Narrative
During takeoff from O'Hare International Airport (ORD), the airplane accelerated normally, rotated, and the captain described that it "jumped into the air." At 800 feet above ground level, the captain called for the climb checklist and noticed an inability to trim nose down. The first officer checked his trim switch and the backup system, but both did not respond. The captain decided to return to ORD.
Both pilots held their control yokes pushed forward to the stop, yet the airplane continued climbing. The captain was eventually able to stop the climb and level the airplane at approximately 8,000 feet. An emergency was declared, and the crew referred to the Pitch Trim 1 and 2 Failure checklists. The checklist directed lowering the flaps to 9 degrees. When the flaps were extended, the airplane pitched nose-high, and the captain reported being "out of control." The captain regained control, and the first officer retracted the flaps.
The landing gear was lowered, which slightly improved stability. The crew pulled and reset the trim circuit breakers twice, with no effect. The captain lined up for an approach to runway 9R but determined he was too high and executed a 360-degree descending turn. Upon completing the turn, the crew deployed the spoilers to slow down. The airplane abruptly pitched up. Both pilots pushed their yokes forward, the captain advanced the throttles, and retracted the spoilers. The captain then banked hard left, 50 to 60 degrees, and chopped the power. Control was regained.
Approach control informed the crew that runway 4R was straight ahead, and the captain elected to land on that runway. The airplane remained configured with landing gear down and flaps and spoilers retracted. The captain flew a long, shallow approach, chopped the power over the runway, and let the airplane settle onto the runway.
Post-Incident Examination
A post-incident examination of the airplane's spoiler control unit revealed that when the spoilers were commanded to retract, the unit did not send an input to the horizontal stabilizer control unit (HSCU) to apply 1 unit of nose-down stabilizer trim. Examinations of the trim system components and other airplane systems revealed no anomalies.
Following the incident, the airplane's manufacturer disclosed that the horizontal stabilizer actuator was determined to be inadequate to move the horizontal stabilizer in all flight conditions. The manufacturer stated that such incidents are "most likely caused when the flight crew fails to trim the airplane after takeoff before reaching a certain airspeed where the air loads on the stabilizer may overpower the trim actuator, resulting in the horizontal stabilizer not responding to the pitch trim command from the flight crew."
Manufacturer and FAA Actions
The manufacturer issued an alert service bulletin mandating the installation of a cockpit placard and revisions to the airplane flight manual establishing a maximum speed of 160 knots to apply pitch trim after takeoff. The Federal Aviation Administration (FAA) issued an emergency airworthiness directive (AD) mandating the same actions. Additionally, the FAA tasked the manufacturer to make design changes enabling the trim actuator to handle increased load limits and mandated improvements for pitch trim failure indications and ergonomic enhancements of the yoke trim switches.