VNAV Descent Path on NGX

[RYR738 9]

Forgive me for being a noob. but the CDU is part of the FMC right?

Yes ! You can't see the FMC's because they are in the E&E bay under the cockpit floor.The CDU's are the interface to them and let you put in info like route, weights, cost index etc. The FMC's are 2 very powerful Flight Management Computers which do all the calculations.

[sho69607 29]

well thats what I have been doing. going into the FMC and deleting certain waypoints from the legs page. I guess this is not what you mean

[RYR738 9]

well thats what I have been doing. going into the FMC and deleting certain waypoints from the legs page. I guess this is not what you mean

Yes, but you must understand that you are deleting them in the FMC by using the CDU.As I said you can't see the FMC's. You should try and fly that route again but don't delete anything. I must go now.Hope I was of help. Fred.

[sho69607 29]

Thank you.

[Foghorn 4]

In a simple form the CDU is to the FMC what your monitor is to your computer...........

[davidz 26]

The FMC's are 2 very powerful Flight Management Computers which do all the calculations.

I wouldn't call them powerful... you can get smart phones with more processing power!

[sho69607 29]

IT HAPPENED AGAIN!! I did not modify the route in anyway and it put me at 11000FT 70 miles away. #####? The fuel is appropriate for the route as well..

[TheGuile 0]

Do you have altitude constraints in your descend? I think the FMC will default to VNAV SPEED DES without altitude constraint.

[sho69607 29]

what are altitude constraints?

[sho69607 29]

?

[pete_auau 1,154]

hi what was your flight plan sid and star see if i can reproduce what you are seeing

[sho69607 29]

Flight Plan was SEATL4 EPH ZOOMR1. Very short flight climb to FL270. Top of Climb was within 30 miles of Top of Descent which started about 105 miles out.

[TheGuile 0]

Altitude constraint are materialized in your LEGS page on the CDU by bigger characterex.There is an altitude constraint at NIRSI you must be Above FL 055at EH608 you must be Above 3400 ftThe smaller font on the altitude for EH607 shows a calculated altitude this is not a constraint

[sho69607 29]

Ya I think I had one of those in the legs page. It was saying drag required, something like immediate descent req after a said waypoint, and descent path unachievable. I believe that was caused by me messing with the waypoints.

[falcon999 24]

Spencer, Its great that your jumping in and trying to use the more complex navigation systems in the NGX. While some of the concepts may seem difficult at first, they can be easily mastered with a bit of homework. Programming a route in the FMC is somewhat complex and you need to understand a few concepts around flight planning and how the AFDS works. The following included documentation can be very helpful: Introduction, Tutorial and the Flight Crew Training manual. Also, AOA is producing a good online training package. As mentioned, the aircraft is following exactly the instructions you have given it. Just entering a STAR doesn't equal the aircraft will descend properly. Typically whats in the NAV database must be modified based on the specific route. You have to pull up the chart and ensure the STAR is entered correctly and the appropriate alt constraints are included. A screen shot of your Legs pages would be helpful.