Incident Summary
On August 19, 2019, a Boeing 787-8 aircraft, registered as SP-LRE, experienced an in-flight anomaly during climb at Flight Level 310. The Engine Indicating and Crew Alerting System (EICAS) displayed a 'LANDING GEAR DISAGREE' message, prompting the flight crew to level off at FL 330 and execute the 'GEAR DISAGREE' checklist. The crew reduced speed to 270 knots and requested holding at waypoint HAPIE to remain within Boston FIR. No emergency was declared.
Flight Details
The 'GEAR DISAGREE' message intermittently appeared and disappeared, cycling 1-2 times per minute. Concurrently, landing gear position indications alternated between 'LEFT MAIN GEAR DOWN/REST UP', 'ALL GEAR UP AND LEFT GEAR IN TRANSIT', and 'ALL GEAR IN TRANSIT'. After consulting with the first officer and the Maintenance Coordination Centre (MCC), the captain decided to return to the departure airport, John F. Kennedy International Airport (KJFK).
During descent at FL 190, the crew extended the landing gear to verify normal extension. Upon full extension, the gear indications returned to normal. Due to the aircraft's weight being near the maximum landing weight, the crew planned an approach to the longer Runway 22R. However, uncertain about the possibility of a safe landing, they executed a go-around, during which the landing gear was retracted. The warning messages and erroneous indications recurred. After completing non-standard and normal checklists, the crew performed a second approach to Runway 22L and landed without further incident.
Cause Determination
The investigation determined that the cause of the incident was intermittent signal transmission in the electrical harness, which disappeared at certain positions within the aircraft, combined with loosening of the intermediate connector socket due to vibration, affecting the connection between the airframe harness and the harness mounted on the landing gear leg.