September 9, 201411 yr I began a flight planning to fly without using the FMC. I did not program the FMC and took off manually. When I reached the altitude and speed I wanted I manually leveled the plane and adjusted the desired speed with throttle setting. The altitude I leveled at was not the same as that set in the mcp alt window. I engaged auto throttle and hit the alt hold switch expecting to see ALT HOLD in the FMA and the plane continue at the current altitude. The plane started a climb and exceeded the altitude in the alt window on the mcp and continued until I stopped it.My understanding is that the plane should have held the altitude the plane was at when I hit the alt hold switch given the alt display was a different altitude. Kevin WIlson
September 10, 201411 yr Commercial Member and hit the alt hold switch expecting to see ALT HOLD in the FMA and the plane continue at the current altitude. So you said what you were expecting, but what did you actually see on the FMA? Kyle Rodgers
September 10, 201411 yr Author So you said what you were expecting, but what did you actually see on the FMA? The FMA showed "ALT HOLD" without the box drawn around it
September 10, 201411 yr Commercial Member The FMA showed "ALT HOLD" without the box drawn around it Hmmm...do you have any hardware trim axes? Kyle Rodgers
September 10, 201411 yr Author Hmmm...do you have any hardware trim axes? Yes, one of the yoke switches is programmed to be aileron trim Kevin Wilson
September 10, 201411 yr Commercial Member Yes, one of the yoke switches is programmed to be aileron trim That's the way it should be. An axis is something like a physical trim wheel, or an actual, movable axis (like how you rock your joystick left/right, and front/back). What you have is button assignments. Those won't conflict with the AP. Kyle Rodgers
September 11, 201411 yr Author Did you have an autopilot on? I assumed I did since the FMA indicated "ALT HOLD", however although I know I hit the CMD button I don't recall if the light went on or not. I recreated the event this time intentionally not selecting CMD and noted that the same thing happened. The plane continued its climb although the FMA indicated "ALT HOLD". I now think that the original problem was that I didn't actually engage CMD and thought the autopilot was on since the FMA indicated "ALT HOLD". The question now is why did the FMA indicate "ALT HOLD" if the autopilot wasn't on. Kevin Wilson
September 11, 201411 yr I assumed I did since the FMA indicated "ALT HOLD", however although I know I hit the CMD button I don't recall if the light went on or not. I recreated the event this time intentionally not selecting CMD and noted that the same thing happened. The plane continued its climb although the FMA indicated "ALT HOLD". I now think that the original problem was that I didn't actually engage CMD and thought the autopilot was on since the FMA indicated "ALT HOLD". The question now is why did the FMA indicate "ALT HOLD" if the autopilot wasn't on. Kevin Wilson The flight director and the autopilot are separate. You can follow the ALT HOLD command from the flight director by using your arms to move the yoke or having the autopilot move the yoke. Even if you have ALT HOLD on, there has to be someone moving the controls if you expect it to stay on the selected alt. Matt Cee
September 11, 201411 yr Even if you have ALT HOLD on, there has to be someone moving the controls if you expect it to stay on the selected alt. Very succinct and polite. I always enjoy your contributions Matt. Dan Downs KCRP
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