The "FLCH trap" was the
sine qua non of the Asiana crash in SFO.
In the Asiana crash, those guys were high on the approach and had 1800' (FAF) set in the MCP while descending in V/S at about 1700 FPM to intercept the visual glide path from above. As they approached 2300', they set 3000' (missed approach altitude) in the MCP and continued to descend. When they got to around 1600', someone erroneously pressed FLCH. Of course, the power levers advanced and the aircraft began to climb to 3000'. The pilot immediately disconnected the A/P and pulled the throttles back to idle. At that point, the system went to HOLD and the throttles never activated to prevent the speed from bleeding off.
In the NTSB hearing, Boeing admitted that they knew about the FLCH trap but decided that after millions of operating hours between the 747/757/767/777/787, and all sharing the the same system, there was no need to change it. So in typical Boeing style, they had some attorneys put a vague note in the AOM warning the pilots about it (no need to give the flight crews any more than we
think they need to know).
As an aside, almost five years prior to the Asiana accident, a 777 forum member here was excouriated and mocked by a number of other pilots when he asked about the very same trap that got Asiana into trouble.
http://www.pprune.org/tech-log/34257...peed-prot.html