Hi to all member of this support forum from Blu236 !!!Today me to write this Topic for find a solution a my problem with fantastic MD 11 on descend.On descend this aircraft not respect the speed in the waypoint !!This is a screen for you. :( An example.The MD 11 for RONDI not respect the speed of 250 IAS and vary to 202 IAS(from where ??)You have a solution for this problem ?Thanks.

In fact, this is an example of how good the MD-11 PROF mode is at managing descent. Note you have a 168kt constraint at PRS, which is only 21nm from SALAP and will require a descent of 285ft/nm. At that descent angle, the aircraft must start slowing down otherwise it will be going to fast at PRS.

Thanks for your rapid reply.Unfortunately the problem is independent from distance of the Waypoint.The my MD 11 is unable of keep all speed and not always the MD 11 respect the altitude.For PRS the original speed is 180 IAS. The 168 IAS is a decision of FMC, not me !!So it is impossible manage ever descent. :( You have other solutions ??

Remember that the speed (if specified) is the upper limit, not the target. As Dan pointed out, you need to lose 7,000 ft AND 92 knots in 6 minutes to met the PRS targets. You are not going to do that if you blast through the next waypoint at 250knts.Also remember that user entered figures are shown in a larger font then FMC calculated figures, so you entered the 250 and the FMC calculated the 168. If you say it was 180 earlier, then something has changed the FMC predictions so it has recalculated. Was that before you enetered the 250? Or did you set the landing configuration or enter the descent forcast? All of this is covered in the manuals and goes to show just how well the FMC works and how easy it is to manage the descent.

And here ?Between GEN and VOG the distance is of 6 minutes.In this axis the MD 11 not respect 285 IAS and the PFD have the speed of the next Waypoint.The problem of the MD 11 is the respect a descend of 7000 Feet to 285 IAS for 6 minutes(all above FL100) ??For me is a failure of FMS.

And here ?Between GEN and VOG the distance is of 6 minutes.In this axis the MD 11 not respect 285 IAS and the PFD have the speed of the next Waypoint.The problem of the MD 11 is the respect a descend of 7000 Feet to 285 IAS for 6 minutes(all above FL100) ??For me is a failure of FMS.

blu236,Nice name by the way.Have flown your "problem into Palermo" and see the same Profile reaction when I change the vertical profile, from the normal STAR, with the constraints at RONDI and SALAP. (wonder where these constraints come from). SALAP/+7000 and PRS/+5000 is normal according charted procedures IIRC.Also the lateral pattern was changed as much as I was able to reconstruct it from the picture provided.I'am interested also to fly 'your' GEN - VOG arrival but for the moment have no time avail.For the time being I would suggest following:With the info that Paul provided, that speed restrictions are not targets, but constraints, program the FMC profile as you did before.However, instead of leaving the controls to the FMC in PROF mode, where 'your MD11' is not doing what you expect,take control of the aircraft yourself and fly the programmed pattern by basic speed and altitude selections.The programmed profile will continue to give you info to show how well you are doing.Regards,Harry

Man you Italians crack me up

Andrei,In my opinion it's not nationality specific.Reading your signature:Having a type rating on any aircraft counts however. Professional statements I mean.Harry

Let the test speed of the descend in Palermo/LICJ.This a rapid reference for "GEN - VOG"(flyght from Rome/LIRF to Milan/LIMC)about the altitude.[The flight plan from Route Finder, LIRF SID GILIO UM729 GEN UM858 VOG STAR LIMC]

This is NOT a bug or a problem! This (as Dan said in the second post in this thread) is an example of how in depth our PROF/VNAV mode coding is - the real aircraft will do exactly what you've seen here. The MD-11 MCDU isn't just a dumb box - it takes into account restrictions that exist further downrange. If what you have entered in is not physically possible for the aircraft to do, it's going to create its own solution to the problem. In this respect it's actually more advanced than a Boeing FMC, which will just disconnect VNAV PTH, throw you into VNAV SPD and give up. It's a general rule with airliners that you can usually either descend fast OR slow down, you can't do both at the same time. That's what you're seeing here, the plane is trying to create a compromise for what it's being asked asked to do. If you don't like what PROF is trying to do, that's what the manual AP modes are for - use V/S, pulled descent etc if you think it should be doing something else.

Ryan said it all. The MD11 FMS creates a vertical path based on a multitude of things (weight, ISA, wind, speed, distance etc etc etc). All speed restrictions are treated as AT OR BELOW. If the FMS cannot "fit" a vertical path within speed restrictions (including fully automatic deceleration for approach) entered then the design/PROF/internal target speed is adjusted to what is possible from a performance point of view. The math behind all this is way and beyond simming stuff so please ask anything you want but also please refrain from using words such as bug because you really don't know how it works internally do you ? The developer who wrote this pretended that the software will go straight into a real box (and adapted for FS treatment of aerodynamics). Do not confuse PMDG planes with other stuff.FYI : In this airplane the FMS will also internally reject altitude restrictions, without any warning, which violate constant climb or constant descent only allowing intermediate level-offs (what a mathematician would call a monotonic path). The MD11 FMC logic is a total "big brother/I know better" type of software watching you and overriding your choices when it sees fit.Note that recent versions of Boeing FMC's will do exactly the same thing with speed restrictions for path computation purposes. The only difference (the Boeing philosophy of not being a "big brother") is that a Boeing plane FMC will warn you. When it comes to entered altitude restrictions violating monotonicity it wont accept them in the first place. You will see all this and more in our new NGx FMC.Hope that answers you question.E M V

The MD11 FMC logic is a total "big brother/I know better" type of software watching you and overriding your choices when it sees fit.

Now it's all good, the screen demonstrate in reality the exact reactiont of the true MD 11.Thanks to all for your rapid answers. :(