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jordanal

MD-11: Top of Descent - Profile Nosedive

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Hi all,Is it just me or do others find that when starting a automatic-profile descent at the TOD, the plane ususally nose-dives somewhere around 4 or 5K/min for the first 10K feet or so? In my case, this is especially true when coming out of a cruise level in the upper 30's. I always have to add at least 2/3 flight-spoilers just to get back in the descent-path for what feels like, an abnormally long period of time. It usually catches backup to the proper descent-path when the descent continues on down through the upper 20's (near the point where FS historically switches from Mach to IAS). Yes, I am inputting the descent-winds on the PERF-DESC page and I don't have this problem in the Queen.It seems that if others are seeing this too (please post if you do)that the descent profile logic might need a bit of investigating in regards to the upper-part of the descent-profile.Thanks for considering,


Regards,
Al Jordan
------------
KMLB

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With me, the MD also starts e steep descent, but only to regain the profile after slowly entering the descent phase. Within a minute it stabilizes back and the descent Mach.Cheers,Xander


Xander Koote

All round aviation geek

1st Officer Boeing 777

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I was surprised by the MD11's relatively shallow descent compared to the Queen. I've seen descent rates of up to -3000fpm but they usually taper off to -2200 in the FL20's.Maybe one difference is the IAS. Default is 290 KIAS, but I'm not sure if that means MMO/290.. I sometimes will enter a different descent airspeed but I learned that both a mach number and a knot number must be entered or it defaults to MMO (max mach operating). This will result in a nose dive to get the speed up. Based on ATC chatter I've heard while flying, I like to select .80/300 or .80/280 if the STAR has a lower speed constraint at a flight level.


Dan Downs KCRP

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