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NTSB issues 10 recommendations after Embraer ERJ-175 pitch control incident
29 January 2020

Based on preliminary findings from its ongoing investigation of a pitch control incident involving an Embraer ERJ-175 airplane, the NTSB issued 10 safety recommendations.

On November 6, 2019, Republic Airways flight 4439, an Embraer ERJ-175 declared an emergency shortly after takeoff from Atlanta-Hartsfield-Jackson International Airport, reporting a pitch trim-related flight control issue and difficulty controlling the airplane. There were six passengers on board the airplane.
The captain and first officer later reported that they both needed to use both hands to counter the airplane’s nose-up pitch motion and that doing so involved such effort that neither felt that they could reach for the QRH to troubleshoot the problem. Ultimately, the flight crew was able to trim the airplane with the first officer’s trim switch, return to Atlanta, and land the airplane safely about 15 minutes after declaring the emergency.

The NTSB issued six safety recommendations to the National Civil Aviation Agency of Brazil (ANAC) and four to the Federal Aviation Administration (FAA). The recommendations are designed to address areas of concern including wire chafing, application of Embraer service bulletins relating to the pitch trim switch, and potential limitations in checklist memory items for pilots to address unintended operation of the pitch trim system.

Although the cause of the incident remains under investigation, post-incident examination of the airplane revealed chafed insulation around wires connecting the horizontal stabilizer actuator control electronics to the captain’s pitch trim switch and autopilot/trim disconnect button. The chafing was caused by contact with the incorrectly untucked pigtail of the forward mechanical stop bolt safety wire.

When the captain’s pitch trim switch was removed from the yoke, marks were observed that indicated at some point before the incident flight, the pitch trim switch had been installed in an inverted position. Embraer previously issued three service bulletins related to pitch trim switch installation error following reports from flight crews in 2015 about flight control system difficulties. However, neither the FAA nor the ANAC required incorporation of the service bulletins. While it is not yet known if inverted switch installation was a factor in the incident, the NTSB is concerned the condition could lead to flight crew confusion, delaying appropriate recognition of and response to increased control forces.

Preliminary information from the NTSB’s investigation also suggests that unintended pitch trim operation may be masked and go undetected during certain phases of flight, such as during takeoff. Further, limitations in the checklist memory items may delay pilots in properly responding to and regaining control of the Embraer ERJ-170/175/190/195 and Lineage 1000 series airplanes. The NTSB is concerned the crew’s application of the memory item(s) on the ERJ-175 Pitch Trim Runaway checklist may not comprehensively address circumstances of the trim system operation in a timely manner.

More information:

Wire chafing to the insulation around wires connecting the horizontal stabilizer actuator control electronics to the captain’s pitch trim switch in an Embraer-175 (left) and an incorrectly untucked pigtail (right) that caused the chafing. Photo courtesy of Republic Airways.

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