What happened
On September 24, 2016, a Boeing 787-800, registration SP-LRC, was operating a flight from New York to Warsaw. While cruising at FL370, the flight crew had the autopilot and autothrottle engaged, with the Flight Mode Annunciator (FMA) displaying speed, LNAV, and VNAV PATH modes. The MCP was set for FL380.
While still within Gander Domestic airspace, approximately 40 NM before the Oceanic Entry Point, the crew received oceanic clearance to climb to FL380. At this stage, the crew had previously engaged ALT HOLD, which had halted any ascent at FL370. In an attempt to program the automatic climb profile into the Flight Management Computer (FMC), the aircraft began an unintended, slow ascent of approximately 100 to 200 feet per minute, climbing out of FL370 toward FL380.
The pilot noticed the deviation and initiated a descent back to FL370. As the aircraft descended through FL375, Gander Air Traffic Control requested a height confirmation from the crew.
The investigation
The investigation focused on the interaction between the flight crew and the FMC during the transition to oceanic airspace. The inquiry examined the cockpit configuration, the automation modes active at the time of the deviation, and the crew workload during the programming of the flight computer.
Findings
- The primary cause of the incident was inadequate monitoring of flight parameters and the pilot's preoccupation with programming the onboard computer while the cockpit was effectively single-pilot.
- A contributing factor was the absence of the second pilot from the cockpit, as one crew member had left to use the lavatory.