777 T/C

[miguelpp 25]

Hi, there

[Guest Phoenix5]

"..8 every 10 times, T/C is wrong, the dinamic ring (target) is always about 20NM before.."I am not sue that I have fully understood the question... on climb the predicted top of climb arc moves out to 20nm from top of descent? How far is your flight? what flight level are you aiming for? What is the optimum flight level for your flight?Could this possibly be due to changes in aircraft speed, or wind speed or other external factor and the aircraft then corrects itself?

[miguelpp 25]

Hi Steven, first of all, i am talking about Top of Climb, and the T/C point is fixed. The arc is moving, and sometimes meet the T/C, but normally it doesn

[SteveA300 7]

Hi Miquel, If I am right your problem is the aircraft is reaching top of climb prior to the point the FMC had previously calculated and more often than not this is 20nm before the predicted top of climb. The predicted top of climb the FMC gives you is just that it is predicted and the aircraft will climb to the cruise alt at the preset speeds and if it can reach top of climb quicker it will. Winds etc can effect the estimated point and if you flew using active sky for instance you would see that there might create a different scenario. During VNAV descents you will see this also the FMC predicts altitudes it will be at certain points, if you manually add a level constraint to comply with atc restrictions for example, be at fl180 at waypoint **** this is no longer an estimate and the aircraft knows it need to calculate a path to be at that altitude at that point. I hope that helps Steve

[miguelpp 25]

That is Steve. Thanks for you answer; i

[SteveA300 7]

I think the issue here is when you model the aircraft do you model correctly an estimated T/C or do you make it similar to a level constraint as thats what people want to see.have fun Steve