Last night I made a flight from EGLL to ESSA using a SID that went to Brockman Park(?). The SID had a number of altitude constraints. However, I wasn

Can't you use the green "kermit line" together with an MCP altitude to get to a particular point at a particular altitude by adjusting V/S?Lee Hetherington (KBED)

Hi Lee.Yepp, the only problem is that as far as I know there is no way of knowing the calculated altitude for a given point in between waypoints during ascent. During descent we have the VNAV path indicator that shows up in the ND, but nothing like that exists during climb. As I mentioned I handled the situation that I got myself into by using LVL CH and changing the speed to what the FMC had calculated when I passed 10 000 ft.I guess I

Reading this I think there are two things to remember:- If you're already above the highest altitude constraint there is no difference in what VNAV and LVL CH do, as long as you set the speed window to the same speed as is suggested in the CLB page. In that sense I don't think there is a path really, that you would have to get back on. Usually you should be able to switch to VNAV right were you are.- However, there is the following note in my Boeing manual: if the airplane is between the FMC target altitude, depicted on the RTE LEGS page for the active waypoint, and the manually entered MCP target altitude, VNAV will not engage. This is logical, since in that situation VNAV wouldn't know which altitude to choose to go to, as it were. Maybe this was the case in your scenario. The solution would be to delete the altitude constraint in the FMC, so that there is only the MCP altitude, in which case VNAV should engage.Leo Bakker

Hi,If in active (VNAV engaged) descent, the DES page will show you- the deviation from path (you also have it depicted on the ND)- the next constraint and its altitude (also on legs page)- the vertical bearing to next constraint- the current flight path angle- the required VS to meet the next restriction.Hope this helpsanthonyAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

Hi Tord,if I don't go wrong didn't they say that soft ALT costraints aren't modelled yet? That could be the case with ALT restrictions on the SIDs. I have had the same problem. In VNAV it would bust though them and then disconnect because it couldn't make the next altitude. I'm sort of confused myself...gotta try it more.Bjorn

Thanks to all for your thoughts. Just to be clear, I was already above any alt constraints in the waypoints that were ahead of me below the cruise altitude, so the soft ALT is no issue in my situation. I had the same altitude in the FMC and the MCP alt window. The only problem was that the pilot (that would be me) had already busted the alt constraints and when I tried to engage VNAV the FMC told me, correctly, that it couldn

In this case to engage VNAV again you would have to wait to pass the last waypoint with the ALT COSTR., at that point VNAV would resume normal climb to CRZ FL. I go as the manual says and use LVL CHG setting the speed bug to flaps up manouvering speed. After I engage the A/P I reset the bug to 250kts. From what I've experienced VNAV doesn't do to good of a job at levelling off at ALT COSTR. even if coming from below nor MCP set altitudes. It's more apparent below 10'000FT where the ROC is greater.Anyway what happened to you I believe it is normal and would happen in real life also.Regards,Bjorn

Well, you could have deleted the next constraint from the LEGS page.That way, the aircraft would not have been above a constraint upon VNAV engagement...At that time, ATC must have been after you already, though ;-)anthonyAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com