I finally found the time this weekend to try this tutorial. Everything went fine until I got to the descent stage, when I got an 'UNABLE NEXT ALT' error in the FMC which I couldn't fix, thereby failing to descend in time to land at KORD. I have three questions:1. Why do you have to change the descent profile in the FMC - I thought the FMC was supposed to work this out itself?2. What did I do wrong?3. I could not get rid of 'UNABLE NEXT ALT' in the scratchpad, so I couldn't fix the problem. How do you get rid of this?I am using the latest update.Thanks for any help. If these questions have been asked before, I apologise, but a search hasn't found the answers (although at least one other person appears to have asked question 3).Regards,John Bolch.

John,You must reset your altitude on the AFDS prior to reaching TOD or you will get that error in the FMC. Once you do this, the error message will clear. This is exactly the way the real 737NG operates.Hope this helps.

Thanks. I thought I did that, as per the tutorial, which tells you to 'Enter 5000 into the MCP ALT Window' before opening the FMC. Are you saying that if I did forget this, I can solve the problem by entering the altitude in the MCP ALT window after getting the 'UNABLE NEXT ALT' message in the FMC, so that the message will then clear? Sorry to ask again but I'm afraid I don't get a lot of time for longer flights, so I'd like to get it right next time!Also, I'm still not clear about my first question: why is it necessary to alter the descent profile in the first place?Regards,John Bolch.

John,Yup, entering the decent altitude will correct the problem. You will probably have to engage VNav again. It's been a couple of weeks since I flew Fred's great tutorial, but I think he put the decent profile change in there to show how it is done. It is not necessary to change the decent profile during a flight. You might also want to get Tim's tutorial. It is fantastic also and goes int great detail.Hope this helps.

Thanks again. I think that answers everything! I'll try the tutorial again as soon as I get a chance, possibly without changing the descent profile, to lessen the chance of error.I agree the tutorial is excellent - I probably wouldn't have gotten off the ground without it! I will try Tim's tutorial after I have mastered Fred's tutorial.Regards,John Bolch.

George,You are correct. I added that descent profile change just to show how it is done. I have found that if I fly on VATSIM with any great regularity, I will not be descending via the FMC profile anyway :)