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Guest tmetzinger

Bug - VNAV does not adjust speed for holds

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I flew today and programmed a hold at 200 knots since we were at 4000.I was in LNAV/VNAV at 250 knots before the hold. When I entered the hold, the airplane tracked the hold perfectly, but did NOT decelerate.Shouldn't the FMC command a deceleration at the holding point?http://forums.avsim.net/user_files/61389.jpghttp://forums.avsim.net/user_files/61390.jpgThe good news is that taking the airplane out of LNAV by pressing ALT HOLD or VS does let me control the speed, and I can put it back in VNAV after I exit the hold?Comments welcome!

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Hi Tim,I just setup a FIX at ENEDY. Route > KWILA (240/4000) ENEDY (240/4000)and ENEDY (HOLD 200/3000) As soon as we crossed ENEDY, VNAV started to decelerate but didn't descent.So Speed here works, but the descent doesn't ... :-roll :-rollBruno Francescoli.

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I've only had to hold once. I just pushed the "Exit Hold" LSK and it took it from there after another pass in the hold.Chris

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Chris,I don't understand what you mean, because EXIT HOLD will EXIT the hold and fly to the next waypoint.Bruno Francescoli.

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I guess I'm confused as to what you are trying to do. I selected my altitude I wanted then hit EXIT HOLD. I descent just as I wanted to. Perhaps you're wanted something else?

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Bruno,Just a wild guess here! ;-)Did you change the MCP altitude to 3000 as well before entering the hold?Tim,I think the speed issue is something looked into for the 800/900. Remembering something mentioned during beta testing about this. But not at all sure here. Maybe someone else can chime in?Cheers,

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>Tim,>>I think the speed issue is something looked into for the>800/900. Remembering something mentioned during beta testing>about this. But not at all sure here. Maybe someone else can>chime in?>>Cheers,I hope someone else can confirm this. I'm going to put my workaround in the tutorial and some comment about the behaviour being "wrong" here, and want to make sure I'm not missing something. From my study of the Bulfer book I believe the airplane should decelerate/reaccelerate as the hold is entered and exited.

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Hi Mats, how are you?> Did you change the MCP altitude to 3000 as well before entering the hold? I think the speed issue is something looked into for the 800/900. Remembering something mentioned during beta testing about this. But not at all sure here. Maybe someone else can chime in ?

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> I believe the airplane should decelerate/reaccelerate as the hold is entered and exited.

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Hi Bruno,I'm fine thanks, and you? ;-)Your findings puzzle me. It seems you managed to decelerate but not descent... Could it be you enterering a hard TGT ALT that it decelerated? I know the FMC is picky about speed constraints without a hard altitude on the LEGS page. Don't know if that's applicable on holds as well. Seems odd though.I am recalling speed was resolved during beta testing. What was left for the 800/900 was proper entry and exit manouevers.Have to check myself... interesting...Cheers,

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I'm good thanks for asking :)> Could it be you enterering a hard TGT ALT that it decelerated?

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I just did another flight to check this on more time.As I entered the data on the FMC, everything looked OK, until I put in the hold (Hold was done at FLL). The altitude and speed of the previous waypoint before the HOLD, although the hold is done at the same waypoint, changed to the HOLD's alt and speed constraint (TGT ALT). Example: FLL intx was 250/4000 (default, small characters, FMC Calculated it) and then FLL HOLD was 210/3000. As I EXECuted that, the FMC changed FLL intx to 210/3000 (small characters)... Why? I don't know. So I put 250/4000 for FLL intx again and checked that 210/3000 was the value at FLL HOLD. Ok. I crossed FLL, entered the FIX. Aircraft slowed down, but maintained 4000ft. I decreased the speed to 200 to check if it was luck or something and again, the aircraft decreased its speed. Changed ALT TGT to /2500 and nothing...aircraft stable at 4000... Bruno Francescoli. "Confused"http://forums.avsim.net/user_files/61572.jpg

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