VNAV Problems

[Guest hicksy]

Hello all,With the release of kai tak 98 I decided to do a flight from RCTP to Kai Tak so that I could do the IGS approach onto RWY13, using the 747-400 in cathay old colours. I set up the FMC with the route (RCTP DCT MKG A1 ELATO CH SL IGS13A180 VHHX) and calculated a zero fuel weight of 466.7 x 1000 lbs. All other information was entered correctly and I confirmed all Vspeeds and set the trim. At first I used a cruise alt of FL380 but had vnav problems so I reset the flight and tried at FL300. The problem is during the take off roll I have the Vnav climb page open on the FMC but as soon as the wheels leave the ground the vnav climb page goes mostly blank except for LSK 1L which has the green boxes to enter the cruise level and when I try to enter the FL it says INVALID ENTRY as a result VNAV wont engage, LNAV has no problems though. Anybody have any answers? they would be greatly appreciated.CheersBrendan Hicks

[cowpatz 243]

Is this the only route it occurs on? What is set on your FMC takeoff page prior to rolling down the runway? What shows on your FMA? CheersSteve

[Guest hicksy]

I have the VNAV CLB page up and it says ACT ECON CLB at the top with all relevant data filled in. It's only when the wheels leave the ground that the FMC deletes all that data and goes back to the green boxes to input cruise alt. I have also tried it on another route (VHHH OCEAN2C V3 KADLO MKG RCTP) and the same thing happened. However, the PMDG 737 FMC is fine and doesnt go blank. Cheers Brendan Hicks