fsxalex 0 Posted December 6, 2014 Share Posted December 6, 2014 Hello all together, when I´m initiating the descent, flying in the managed mode of A318/319, the MCDU is calculating a higher speed than the cruising speed. I´m wondering if this is okay?. In the A320 it is not the case which is normal for me. Is there a bug do I make a mistake during setting up the MCDU. Thanks in advance for your help Link to comment Share on other sites More sharing options...
Deputy Sheriffs The Dude 6537 Posted December 6, 2014 Deputy Sheriffs Share Posted December 6, 2014 Cruise speed is normally in Mach. At the higher FL's the IAS reduces for the same mach number. During descent the IAS will increase again for the same mach number. We have seen no abnormalities with the way we modelled it. If you still feel it is a problem just post some screenshots of the CRZ phase and the DES phase showing the IAS on the PFD and the CI on the MCDU. Happy Landings Link to comment Share on other sites More sharing options...
uadriver 6 Posted February 19, 2015 Share Posted February 19, 2015 frank can i digress a little and ask about an apparent anomoly with the A320IAE at least. as you can see on the images, managed speed calculated by the FMGS in CLB mode & as shown on the flight plan is 287, much as i expect for a smiths CI of 30. the CLB PERF page though is much higher .. 30kts more. this higher speed is set on the FMA & flown. towards TOC, this extra speed is pushing crossover mach over 0.8. there is a similar issue on managed descent ... the FMA setting a higher speed than the MCDU plan shows. your thoughts please ! cheers john Link to comment Share on other sites More sharing options...
Joshua Che. 1601 Posted February 19, 2015 Share Posted February 19, 2015 frank can i digress a little and ask about an apparent anomoly with the A320IAE at least. as you can see on the images, managed speed calculated by the FMGS in CLB mode & as shown on the flight plan is 287, much as i expect for a smiths CI of 30. The speed predictions may not be a bug, because the FMGS assumes ISA standard atmosphere, resulting in a different mach cross over than actual conditions. I will check it further though. Link to comment Share on other sites More sharing options...
uadriver 6 Posted February 19, 2015 Share Posted February 19, 2015 joshua thanks for the note ..... i thought crossover speed / mach should occur as per the perf page but that the crossover altitude will vary with ISA variance. crossover is happening, just that it seems at a higher mach than the perf page shown, thus at a higher altitude. that aside, i am more interested in hearing thoughts on the difference in CLB (but not DES) mode why the MCDU PLN speed profiles is different to the PERF page speed ... in managed speed mode. DES is fine !! cheers john Link to comment Share on other sites More sharing options...
uadriver 6 Posted February 25, 2015 Share Posted February 25, 2015 ..... i am more interested in hearing thoughts on the difference in CLB (but not DES) mode why the MCDU PLN speed profiles is different to the PERF page speed ... in managed speed mode. DES is fine !! joshua a quick note to mention i'm seeing this anomoly in all versions of the a320/321 .... & i remain curious why it has not been posted earlier, or perhaps i searched with the wrong keyword/s. cheers john Link to comment Share on other sites More sharing options...
uadriver 6 Posted April 1, 2015 Share Posted April 1, 2015 joshua any news on my post #6 .... ?? cheers john Link to comment Share on other sites More sharing options...
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