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B777-200 first officer reported after a normal preflight; and before takeoff; the MCP speed window went from 170 to 150 uncommanded.
| Attributes | |
| ACN | 1102155 |
| Time | |
| Date | 201307 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | ZZZZ.Airport |
| State Reference | FO |
| Aircraft 1 | |
| Make Model Name | B777-200 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Taxi |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | MCP |
| Person 1 | |
| Function | First Officer Pilot Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe |
Narrative:
1) preflight normal; MCP set-up for departure; MCP speed set at 170 KTS. 2) aircraft push back from gate. 3) engine start as per normal procedure. 4) after engine start; taxi clearance. 5) moments after; MCP speed window went from 170 to 150 without any human intervention. 6) none of us touched the MCP speed control knob; or any area on the MCP! 7) I reset the MCP speed to 170 KTS. 8) flight proceeded normally without any other MCP issue. 9) landed - speed intervene during approach; no other anomaly noted on MCP. 10) event written up in logbook.none of us touched the MCP speed control knob; MCP panel; or anything else in any way when this event took place - speed just flipped from 170 to 150 - not good. An extensive study should be made of the software that controls the MCP display. This is the second event that I personally know about; and it is reported to me that [other airlines] have had similar events. There is definitely a bug in block point 14 as it relates to the speed set in the MCP speed window; and it needs to be fixed before this event happens in flight and becomes a causal factor in a catastrophic event.
Original NASA ASRS Text
Title: B777-200 First Officer reported after a normal preflight; and before takeoff; the MCP speed window went from 170 to 150 uncommanded.
Narrative: 1) Preflight normal; MCP set-up for departure; MCP Speed set at 170 KTS. 2) Aircraft push back from gate. 3) Engine start as per normal procedure. 4) After engine start; Taxi clearance. 5) Moments after; MCP speed window went from 170 to 150 without any human intervention. 6) None of us touched the MCP speed control knob; or any area on the MCP! 7) I reset the MCP speed to 170 KTS. 8) Flight proceeded normally without any other MCP issue. 9) Landed - speed intervene during approach; no other anomaly noted on MCP. 10) Event written up in logbook.None of us touched the MCP speed control knob; MCP panel; or anything else in any way when this event took place - Speed just flipped from 170 to 150 - Not good. An extensive study should be made of the software that controls the MCP display. This is the second event that I personally know about; and it is reported to me that [other airlines] have had similar events. There is definitely a bug in Block Point 14 as it relates to the speed set in the MCP speed window; and it needs to be fixed before this event happens in flight and becomes a causal factor in a catastrophic event.
Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.