NTSB · Safety Recommendation
Safety Recommendation A-20-002
Recommendation
TO THE CIVIL AVIATION AGENCY OF BRAZIL: Once Embraer develops inspection instructions for the wiring in the captain’s and first officer’s control columns as requested in Safety Recommendation A-20-1, require operators of Embraer EMB-170/175/190/195/Lineage 1000 series airplanes to inspect that wiring for damage, in compliance with Embraer’s instructions, replace where needed, and ensure proper clearance from adjacent components, including the forward mechanical stop bolt and its safety wire.
Safety Issue and Context
On November 6, 2019, the flight crew of Republic Airways flight 4439, an Embraer EMB-175, declared an emergency shortly after takeoff from ATL with six passengers on board, reporting a pitch trim-related flight control issue and difficulty controlling the airplane. The captain (who was in the left seat and the pilot flying) later reported recognizing the flight control issue after a failed attempt to engage the autopilot about 2,200 ft mean sea level.
The captain stated that he conducted the single memory item on Republic’s Pitch Trim Runaway checklist to push and hold the autopilot/trim disconnect button on his side (figure 1 shows Republic’s quick reference handbook [QRH] checklist for a pitch trim runaway).1 The captain then asked the first officer to push and hold the right-side autopilot/trim disconnect button. The flight crewmembers reported that they did not notice any change in the pitch condition and continued to have difficulty holding the nose down.
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 ATL, and land the airplane safely about 15 minutes after declaring the emergency.
Review of data from the incident flight revealed that the airplane was in a mistrim condition for a portion of the flight. While this incident is still under investigation, three areas of concern have been identified: wire chafing, application of Embraer service bulletins (SB) related to the pitch trim switch, and potential limitations in checklist memory item(s) to help Embraer pilots address unintended operation of the pitch trim system.
Response History
February 24, 2025 · NTSB Correspondence · Foreign, Brazil, Departamento de Aviacao Civil
We note that a significant number of operators of Embraer EMB 170/175/190/195/Lineage 1000 series airplanes have voluntarily completed the inspections specified in Service Bulletin (SB) 170-27-0058 (EMB 170/175) and SB 190-27-0045 (EMB 190/195/Lineage 1000), which were developed in response to Safety Recommendation A-20-1. We also note that you do not plan to require Embraer’s SBs because you are not aware of any damaged wiring that has been reported as a result of those inspections.
We continue to believe that all affected airplanes should be inspected, as specified in Embraer’s SBs. We point out that, after chafed wires were found on the incident airplane, the operator voluntarily inspected the rest of its fleet and found nine airplanes with chafed wiring, and a different operator found damaged wiring on one of its airplanes. We are concerned that damaged wiring could be present on additional airplanes that have not been inspected and, if undetected, could lead to electrical shorting and adversely affect systems mounted on the control column and yoke. However, you did not report any plans to verify that the remaining affected airplanes have been inspected.
Accordingly, the Board has classified Safety Recommendation A-20-2 CLOSED-- UNACCEPTABLE ACTION.
May 13, 2024 · Recipient Response · Foreign, Brazil, Departamento de Aviacao Civil
-From Major General Marcelo Moreno, Chief of the Aeronautical Accident Investigation and Prevention Center: As requested by ANAC, EMBRAER followed the accomplishment of the Service Bulletins 170-27-0058, 190-27-0045 and 190LIN-27-0021 by aircraft operators, which were developed for inspections according to recommendation A-20-1. A significant number of inspections were voluntarily accomplished by worldwide operators, not only from Brazil, with no findings. There are also field data from MRBR task Z220-003 accomplished at the same area of the service bulletins mentioned with no related findings, suggesting that there is no general related issue affecting the fleet.
In addition, the manufacturer published the number of the Service Bulletins on the list of Special Attention Items to notify all the worldwide operators of the relevance of their accomplishment, so ANAC concluded that there was no need to issue a Special Airworthiness Bulletin. FAA and other authorities were notified by ANAC of the results of the recommended actions by email and Service Difficulties meetings. ANAC considers that there had been no findings except at Republic and no evidence of a direct relationship between the chafed wire and the movement of the horizontal stabilizer.