B777-200
Human-Machine Interface; Confusion
Aircraft Equipment Problem Less Severe; Deviation - Altitude Overshoot; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action; Flight Crew Became Reoriented
Human Factors; Aircraft
On arrival to EDDF; we were cleared to cross RAMOB at FL110. FL110 was set in altitude window and confirmed by pilot flying and pilot not flying. Subsequently received call from ATC verifying crossing restriction when realizing we were passing FL107. At that time discovered FL100 had appeared in altitude set window without pilot input. Returned to FL110 and continued without further incident and no further comment from EDDF ATC.I suggest we monitor/crosscheck automation and aircraft performance; avoid distractions.
A B777 was cleared to cross RAMOB Intersection on the EDDF arrival at FL110. Both pilots confirmed the MCP altitude window at FL110 but somehow FL100 became active so ATC called about the aircraft's failure to level at FL110.