I've been doing a few practice flights with the 773ER to improve my hand-flying skills. While doing this, I came across an oddity in the way trim responds with the F/D on versus with it off.
Since I only fly out and back, I set the altitude (both the FMC cruise altitude and the MCP altitude) to only 8000 feet or so. While climbing out, I tried to level off early at about 6000 feet. I noticed that, if I had turned the F/Ds on before takeoff, the aircraft would not respond to nose-down trim at all. The only way I could hold altitude was to push forward on the stick. Once I reached 8000 feet and the pitch mode changed away from "TO/GA", I could trim the airplane normally.
I tried another climb-out and level-off without turning on the F/Ds before takeoff, and in this case the airplane responded to trim normally. Is this normal? I noticed in the "Introduction" document that there is a reference to "hands-off speed stability *or* path hold modes" (emphasis mine) in the section describing the control column null zone. Is what I am experiencing with the F/Ds on the "path hold" mode? I tried digging around in the FCOM but couldn't find anything (though I certainly may have missed it).
Thanks in advance for your help!
