History of Flight
On November 6, 2019, about 2115 eastern standard time, Republic Airways flight 4439, an Embraer EMB-175LR (N117HQ), experienced a pitch trim anomaly shortly after takeoff from Hartsfield-Jackson Atlanta International Airport (ATL), Atlanta, Georgia. The flight crew declared an emergency and returned to ATL. The nine passengers and crewmembers aboard the airplane were not injured, and the airplane was not damaged. The flight was a regularly scheduled passenger flight destined for LaGuardia Airport (LGA), New York, New York, operating under 14 Code of Federal Regulations Part 121.
The flight crew reported for duty on the day of the incident about 1400 at Detroit Metropolitan Wayne County Airport (DTW). The incident occurred during the third flight leg. The captain flew the first leg from DTW to LGA. En route, the engine indicating and crew alerting system (EICAS) annunciated a “PITCH TRIM SW 1 FAIL” message. The crew referred to the quick reference handbook and noted the message as advisory; they recorded it in the logbook for maintenance action at LGA.
At LGA, maintenance personnel initially planned to replace the captain’s pitch trim switch, but after partially removing the switch, they deferred the maintenance per the minimum equipment list. They reinstalled the switch without a functional test and placarded it as inoperative. The crew was advised to use the backup trim switch.
The first officer flew the second leg from LGA to ATL without issues. No further maintenance was performed at ATL.
For the third leg, the captain was pilot flying. After a normal taxi and takeoff at 2105:05, the first officer noted a climb rate of about 4,000 ft per minute, normal for the light load. At about 2,200 ft mean sea level, the captain could not engage the autopilot. He instructed the first officer to declare an emergency at 2106:53. The captain suspected a pitch trim runaway and performed the memory item from Republic Airways’ runaway trim emergency checklist: pushing and holding the autopilot/trim disconnect button on his yoke. The captain kept both hands on the yoke to control the airplane and asked the first officer to push and hold the disconnect button on his yoke, but no change in pitch condition was observed. Both pilots had to push forward on their control columns to prevent pitch-up.
Flight data recorder (FDR) data showed the horizontal stabilizer initially at about 4° nose up, then moving to a maximum of 13° nose up between 2105:50 and 2107:45. Multiple trim-up commands from the captain’s switch were recorded, with only one trim-down command from the first officer’s switch. The airplane experienced pitch oscillations reaching a maximum pitch-up attitude of about 27°. At 2108:15, the crew reported a stalling situation; about one minute later, they reported inability to pitch down. The captain pressed the cutout button for pitch trim system 1 (associated with the earlier EICAS message). At 2110:36, the stabilizer parameter suddenly went to 0°, consistent with trim cutout actuation. According to Embraer, pressing one cutout switch does not stop stabilizer movement; both must be pressed. The first officer stated airspeed dropped to 138 knots before control was regained.
After 2110:40, multiple trim-down commands from only the first officer’s switch were recorded, and by 2116:40, the first officer was able to trim nose down and regain airspeed. The captain transferred control to the first officer to talk with ATC and troubleshoot. The airplane landed uneventfully about 2125.
Aircraft Information
The Embraer EMB-175LR uses a horizontal stabilizer control surface for pitch trim, moved by a dual-motor actuator. Manual pitch trim switches are on each control yoke and a backup switch on the center pedestal; all are dual-split switches. Two stabilizer cutout switches on the center pedestal can lock the actuator if both are pressed; pressing one allows normal operation. Autopilot/trim quick disconnect buttons on each yoke, when held and both cutouts normal, prevent manual or autotrim commands and disengage the autopilot; if one cutout is pressed, the associated disconnect button does not function.
Republic Airways’ quick reference handbook listed one memory item for pitch trim runaway: press and hold the autopilot/trim disconnect button. The Embraer 170/175 Airplane Operations Manual required two memory items: press and hold the disconnect button and push both cutout buttons.
Maintenance History
Review of flight logs from August 7 to November 5, 2019, revealed multiple discrepancies related to the pitch trim system, including repeated “Pitch trim switch 1 fail” EICAS messages. Corrective actions included replacing the captain’s pitch trim switch and horizontal stabilizer actuator control electronics, and multiple operational checks. The switch was deferred several times under the minimum equipment list. Between May and November 2019, Republic Airways submitted 15 mechanical interruption summary reports to the FAA for the incident airplane.
During the incident flight, the captain’s pitch trim switch was placarded inoperative and deferred, with no requirement to disconnect or disarm it.
Post-incident maintenance found fault code 27430200HS2 (loss of power to channel 1 of the HS-ACE), consistent with activation of the channel 1 pitch trim cutout switch during the flight.
Post-Incident Findings
After the incident, maintenance personnel confirmed correct operation of all three pitch trim switches per the Aircraft Maintenance Manual. No anomalies were observed. The captain’s yoke pitch trim control inputs were disconnected, and the aircraft was ferried to Indianapolis on November 9, 2021, with no anomalies noted. In Indianapolis, wire inspections identified damaged wiring at the base of the captain’s control column. Examination revealed wires with chafed insulation connecting the horizontal stabilizer actuator control electronics to the captain’s pitch trim switch and disconnect button. The wires contacted an incorrectly tucked pigtail on the safety wire retaining the captain’s control column forward mechanical stop bolt. Laboratory testing showed insulation damage to three wires: the quick disconnect switch (severed strands), nose-up trim switch A (chafed with visible conductor), and nose-up trim switch B (chafed with strands not visible). No arcing was observed. Examination of the pitch trim control switch revealed an imprint mark on the back, consistent with the switch having been installed inverted at some point.
Embraer Service Bulletin 170-27-0051, issued February 27, 2015, alerted operators to the possibility of inverted pitch trim switch installation and recommended installation of a support; compliance was 7,500 hours or 36 months. This bulletin had not been performed on the airplane before the incident. In response, on April 13, 2020, Embraer and the FAA revised the master minimum equipment lists to remove yoke pitch trim switches from deferrable items.