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ahinterl

MD-11 (FSX): Strange situation at T/D

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To assist the plane in descent, I dialed 5000 into the altitude window and approximately 5 NM from the T/D, I pulled the altitude knob. The plane lowered the nose, FMA indicated IDLE CLAMP. I thought it would be interesting to see what happens if PROF would be re-engaged, so after some seconds, I pushed PROF. The plane leveled instantly with HOLD 5000 announced in white.I didn't expect that behaviour and again pulled the altitude knob - without any effect. Pushing PROF again didn't have any effect too, so the only way to get a descent back was V/S mode. After a while in V/S, pushing PROF cleared up the situation and I was back on a managed descent.Can someone please tell me why a FLCH wasn't possible and why the plane leveled off when I pushed PROF?Andreas

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Were you below the VDS (vertical deviation scale)? The G/S looking thing on the Map? I don't know how the logic is supposed to work in that case, but it seems like engaging PROF after using LVL CHG has worked with me in the past just fine.I would think HOLD should switch back to PROF in magenta, or HOLD in magenta if a constraint was captured. It sounds like the Alt knob was pushed. You sure that didn't happen? Maybe the logic was acting up. I've had strange things happen like that on all add ons.

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I think that PROF. Is doing the same job as LVLCHG in Boeing, so if you set 5000 and pressed PROF or Pulled the knob both will do the same thing as you want to desc. to 5000 feet, but if you set the ALT setting to your final level or level higher than you are, I think different thing will happen, Like Climbing.Maybe those words are useful, and if I am wrong anyone that have more experience can correct me.Regards.Ibrahim Nassef

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Ibrahim, I beleive the PROF stands for Profile, and lets the aircraft follow the calculated vertical profile. The Idle Clamp would be more like the level change on Boeing aircraft, the aircraft sets throttle to flight idle, and decends as fast as it can to hold the current speed.RegardsWerner Rafteseth

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The strangest thing was that being at FL200 and having 5000 in the altitude window, and the plane flying level after pushing PROF, pulling the altitude knob didn't do anything at all!I can hardly think that the altitude knob becomes inoperable at any time under normal circumstances. No matter what flight mode one is active, pulling the altitude knob with a different altitude in the altitude windows should always do something, that's how I understood the systems.In my situation it was just like I pulled a dummy knob. Neither the FMA changed, nor did the AFS and ATS anything. V/S was my only rescue.To answer your questions: I was not at the T/D position yet, so the vertical deviation indicator was not even active. I even guess I'd have no vdev indicator at all during a FLCH.I pulled the altitude knob for FLCH, the plane started a descend with IDLE CLAMP, I pushed PROF, the plane leveled, I pulled again for FLCH, absolutely no reaction, I pushed PROF again, no reaction as well, then I turned the v/s wheel and finally got the plane to descend again.If you ask me: This cannot be normal!Andreas

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To assist the plane in descent, I dialed 5000 into the altitude window and approximately 5 NM from the T/D, I pulled the altitude knob. The plane lowered the nose, FMA indicated IDLE CLAMP. I thought it would be interesting to see what happens if PROF would be re-engaged, so after some seconds, I pushed PROF. The plane leveled instantly with HOLD 5000 announced in white.I didn't expect that behaviour and again pulled the altitude knob - without any effect. Pushing PROF again didn't have any effect too, so the only way to get a descent back was V/S mode. After a while in V/S, pushing PROF cleared up the situation and I was back on a managed descent.Can someone please tell me why a FLCH wasn't possible and why the plane leveled off when I pushed PROF?Andreas
Note: top of page FMS 50.3 ??Harry

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