747 - FMC program error

[Guest castleberg]

Hello Yesterday I was flying the Queen from KLAX to KMIA. I was on the descent, kind of a downwind leg. I had programed an East Approach and an appropriate STAR on the LEGS page. I also programed the missed approach procedure on the LEGS page. In order to get a more convenient intercept angle of the ILS I decided to use another waypoint on the downwind leg. I was not vectored. I've chosen the same waypoint XXXXX that was used as HOLD point after the missed approach procedure. This is why I downselected this point into the scratchpad and upselected it as a direct-to-point. And there the plane turned directly towards it as it should. However the LEGS page became almost blank, the whole approach and runway information being whipped out, with only XXXXX left. Then I went to the DEPARR page and tried to programm the approach once again. After selecting the appropriate RWY an immediate program error appaered on the scratchpad. It was no longer possible to select any runway for landing. What I had to do was a (certainly forbidden and non existing) mixture of a LNAV and visual-approach. What has gone wrong? Is this the way the FMC is supposed to behave?Thanks a lot for your help. Tom

[Tabs 2,790]

Tom,If you can reproduce this, save a flight with instructions and mail to me at rmaziarz@precisionmanuals.com

[Guest castleberg]

Hello RyanThanks for your quick reaction. I'have the descent saved. I'll try again and if I can reproduce the error I will save it and send it to you with instructions. I can halfway understand that the FMC LEGS page cleared all datas after downselecting the final HOLD point of the ma-procedure and upselecting as a direct-to point. BTW: After that happened the primary EICAS showed G/A as thrust mode. So it acted as if I was already on the go-around. ThanksTom