VNAV - Programming restrictions are not honored...

[Guest crosswinds]

Hi all,The VNAV does'nt maintain speed restrictions under FL100 of 250kts. Before take-off I enter the restriction into the FMC and just past 3000ft the magenta marker skips up to something close to 270kts and the speed bar follows course.Also upon descent when I enter the same restriction(240/10000) the aircraft doesnt decel to honor restrictions.In both cases I switch to FLCH to keep things in place. Any help on the issue would be appreciated.Thanks,Jay

[emvaos 13]

Dear Jay,VNAV will always go for minimum VRef30+100 in clean config. Always.Best,Vangelis===================================== E. M. Vaos Precision Manuals Development Group www.precisionmanuals.com=====================================

[Tabs 2,790]

To explain further, basically you're too heavy for 250 or less to be a safe clean airspeed. If you were to load the plane light with little fuel, you'd see it be able to to stay at 250 - this is realistic and real life ATC does not hold 747's or other extremely heavy aircraft to the 250 under 10k regulation. The rule is not an absolute, safety always comes first.

[Guest crosswinds]

Vangelis, Ryan,Thanks for the info, reflecting back on the cockpit situation at those times it makes perfect sense for the VNAV to behave that way - very justified.Its just with the Flight Keeper running in the background that pulls the score lower! ;)Thanks much gents!Best,Jay

[Guest afluhart]

>Vangelis, Ryan,>>Thanks for the info, reflecting back on the cockpit situation>at those times it makes perfect sense for the VNAV to behave>that way - very justified.>>Its just with the Flight Keeper running in the background that>pulls the score lower! ;)>>Thanks much gents!>>Best,>>JayA work-around I o which is not really all that realistic... is i keep the flaps at 5 until I reach the 10,000 ft limit... i use FsP though and i have the ability to disable that penalty if I choose to.

[Mats_J 2]

Hi Anthony,>A work-around I o which is not really all that realistic... is>i keep the flaps at 5 until I reach the 10,000 ft limit... i>use FsP though and i have the ability to disable that penalty>if I choose to.This is exactly what the real drivers want to avoid. They want to get the ship clean as soon as possible and thus will exceed 250 below 10000 if weights and other operational parameters dictate so.But yeah it is a workaround. ;-)Cheers,