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Guest nigvilla

FMS Order at TOff & Climbout

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I have followed Tutorial but am still a bit confused regarding how the FMS handles speeds during T Off and Climbout.I find that the speeds tend to 'stick' at V2 +10 unless I push FMS Speed. The tutorial gives me the impression that all should happen automatically once Auto Flight and Nav selected?

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Nigel, The AUTOFLIGHT will just engage the autopilot (and autothrottles if not already armed on the ground).NAV will engage lateral guidance only (the equivalent of Boeigs LNAV).FMS SPD sets the calculated FSM speed, so it must be engaged to allow for acceleration to the speed limit (250/10,000) once above 3,000 ft from airport elevation.PROF is the equivalent of the Boeings VNAV (with the difference that it does not control speed, this is done by the FMS SPD). Take-off is a special mode, and initially, even though you have not engaged FMS speed, you will have magenta (FMS computed) speed targets at V2 on the ground and then V2+10. This mode ends at acceleration altitude, so you have to engage FMS SPD mode if you want to continue to have speed controlled by the FMS. Of course you don't have to wait, you can do that earlier and speed will automatically change at acceleration altitude. Also note that during take-off only, when you engage PROF mode, FMS SPD mode will be automatically engaged as well. Hope this is not too confusing, if you get used to it it is very convenient after all.

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Michael,Thanks for that. I am more convinced now that the tutorial misses the point about engaging FMSSpeed.

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>This mode ends at acceleration altitude, so you have to engage>FMS SPD mode if you want to continue to have speed controlled>by the FMS. I think Nigel is correct, the tutorial misses this step.You must engage FMS SPEED on climbout at some point or else you could end up in trouble.RhettFS box: E8500 (@ 3.80 ghz), AC Freezer 7 Pro, ASUS P5E3 Premium, BFG 8800GTX 756 (nVidia 169 WHQL), 4gb DDR3 1600 Patriot Cas7 7-7-7-20 (2T), PC Power 750, WD 150gb 10000rpm Raptor, Seagate 500gb, Silverstone TJ09 case, Vista Ultimate 64ASX Client: AMD 3700+ (@ 2.6 ghz), 7800GT

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Nigel & Rhett,The tutorial does not mention this because if you engage PROF mode at 1,500 ft as it suggests (which is below the acceleration altitude of 3,000 ft) FMS SPD mode will automatically engage.However, you are right, it should mention that the FMS SPD mode is engaged independently of the PROF mode in all other cases except the take off phase.

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The best thing to do is to arm NAV and PROF before take off. In that case you will get climb thrust and speed acceleration automatically :)

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Ah I didn't know that, thanks fellas. The MD-11 climbs so quickly I will have to be faster to engage PROF before 1500 ft.It climbs so quickly because I am sure I am not de-rating enough, and I also have not flown with a heavy load yet. I still haven't quite gotten a handle on FLEX settings, but that's a different matter...RhettFS box: E8500 (@ 3.80 ghz), AC Freezer 7 Pro, ASUS P5E3 Premium, BFG 8800GTX 756 (nVidia 169 WHQL), 4gb DDR3 1600 Patriot Cas7 7-7-7-20 (2T), PC Power 750, WD 150gb 10000rpm Raptor, Seagate 500gb, Silverstone TJ09 case, Vista Ultimate 64ASX Client: AMD 3700+ (@ 2.6 ghz), 7800GT

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