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Guest ntsmith

Descent phase; what am I doing wrong ?

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Guest ntsmith

I cannot understand what I am doing wrong here. When I am first told to start to descend (say to FL X) I select the new altitude on the MCP then LVL change. What happens then is I have an aircraft that would frighten the #### out of the pax. OK, its controllable by using the VS control but surely VNav should sort things out.I have the FMC set to PATH and NOT SPD but isn't I thought speed is not speed of rate of descent.Can anyone help so that when I want to go down I don't go down at 4000fpm ?Kind regardsNigel Thomas-Smith

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Are you using LVL change or VNav? At first you said LVL change, but then you say, VNav should sort it out. I'm confused.


Mike Roth

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Guest ntsmith

Confused ? Yes. So am I.With the new altitude dialed into the box (above the altitude select box selector switch) I then select LVL CHG but it then more often than not descends like a brick, rather akin to EXPEDITE on the A300 bird. I have to go to the vertical speed selector before it gets too high.Hope that is clearer.Kind regardsNigel Thomas-Smith

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If you're in VNAV and you reset the MCP altitude to your desired new level before the TOD point, then the aircraft should initiate a descent automatically, following an optimum profile. You can then control the airspeed by clicking on the centre of the IAS knob to enter airspeed intervention mode.The optimum descent path can sometimes entail a fairly rapid descent though.


Mark Adeane - NZWN
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Guest ntsmith

does that mean it should start to descend from the TOD or immediately after MCP altitude has been reset. Without selecting ALT CHG ?Kind regardsNigel Thomas-Smith

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If you set the MCP alt from say 35,000 to 10,000 and don't do anything else (ie leave the AP in VNAV) then the descent will start automatically at the TOD point, not before. There is no need to use ALT CHG that I'm aware of.


Mark Adeane - NZWN
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>I cannot understand what I am doing wrong here. When I am>first told to start to descend (say to FL X) I select the new>altitude on the MCP then LVL change. What happens then is I>have an aircraft that would frighten the #### out of the pax.>OK, its controllable by using the VS control but surely VNav>should sort things out.>I have the FMC set to PATH and NOT SPD but isn't I thought>speed is not speed of rate of descent.>Can anyone help so that when I want to go down I don't go down>at 4000fpm ?>>>>Kind regards>Nigel Thomas-Smith the AFDS (Minus V/S selected) does not take PAX comfort into account whatsoever, that's the pilot's job and is very realistic.[h4]Randy J. Smith[/h4]AMD 64 4000+|ASUS K8V DELUXE|SAPPHIRE ATI X800XT PE|MUNCHKIN 3200|80 gig SATA|DELL 1905FP 19" LCD|TRACKir PRO|PFC JEPPESEN MOONEY YOKE|CH PRO PEDALS|


Randy J Smith

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