The captain was the pilot flying and the first officer (FO) was the pilot monitoring. According to the flight crew, the visibility at IAH was forecast to be poor due to fog. Based on the conditions at IAH, the flight crew elected to perform a Category III (CAT III) approach and landing using the airplane’s autoland system. The flight crew recalled no issues during the approach. When the airplane touched down, the captain stated he confirmed the engine thrust levers were at full idle. The captain recalled the speedbrakes deployed, and as he moved to raise the thrust reversers, he noted that the nose of the airplane rose unexpectedly. The captain manually pushed the control column forward with enough force to both disconnect the autopilot and lower the nose, but pulled the column back to prevent the nose landing gear from “slamming down.” The FO recalled the touchdown was smooth and recognized the speedbrakes had deployed. The FO was looking at the flight mode annunciator (FMA), located at the top on the primary flight display (PFD), and called out that the system entered takeoff/go around (TOGA) mode. The FO recalled the three fields for the FMA showed the following from left to right: 1) a blank field, 2) TOGA, and 3) TOGA. The captain and FO did not recall the TOGA switch was pressed. The flight crew recalled the pitch attitude rose to about 7.5° on the PFD. The flight crew did not recall any further issues during the remainder of the landing roll.

While exiting the runway, the captain recalled seeing a “tailstrike” message on the engine indicating and crew alerting system (EICAS). Postlanding inspection of the airplane confirmed substantial damage to the lower fuselage consistent with its contact with the runway. Additionally, scraping damage was found on the tailstrike sensor and on an antenna on the lower fuselage. There was no reported mechanical malfunction that contributed to the excessive airplane pitch angle after the airplane touched down.

The recorded flight data showed that the autopilot pitch mode and autothrottle mode were both in “flare” mode at the time the airplane touched down on the runway. About half a second after touchdown, the flight data showed the TOGA switch was pressed. As a result, the autopilot pitch and autothrottle modes both transitioned to TOGA mode. The autothrottle TOGA mode was canceled when the throttles were moved to reverse thrust. The autopilot pitch mode, still in TOGA mode, commanded the elevator and stabilizer to target a go-around pitch attitude, with the pitch attitude increasing from 3.5° to 7.4° over 2 seconds.

5 seconds after TOGA mode was activated, the control column was pushed forward (airplane nose down) and 2 seconds later showed a peak control column force of 40 pounds, which disconnected the autopilot. At that time, the airplane pitch attitude reached 7.8°, sufficient to result in a tailstrike, with a subsequent peak value of 7.9°. The flight data also showed the tailstrike protection function had activated and was commanding an elevator deflection, after the TOGA switch was pressed, to reduce elevator deflection. However, the tailstrike protection function could not prevent the pitch attitude increase that resulted in the tailstrike due to its limited authority.

They did not recall pressing the TOGA switch and did not believe they pressed them. There was no evidence of an autopilot system malfunction, therefore it is likely the captain inadvertently pressed the TOGA switch when he reached for the thrust reversers at touchdown. According to the airplane manufacturer, the conditions that inhibit TOGA activation were not yet satisfied when the TOGA switch was pressed, allowing for both the autopilot pitch mode and autothrottle mode to transition to TOGA. The flight crew was unaware that TOGA mode was activated, and their delayed detection of the increase in pitch attitude prevented timely application of corrective pitch control inputs to avert the tailstrike.