744 VNAV Descent Issues.

[Guest Totalbeginner]

I'm operating the -400 and the -400F which are both up-to date but I am still having problems performing a VNAV descent.Problem 1. If I'm cruising below the OPT cruise height then the aircraft will need to decelerate. As expected, a few miles from the TOD the throttles retard and the speed bug moves to the ECON speed for descent. But as the the aircraft slows, the bug flicks between descent and cruise speed causing the engines to throttle up and down, why?Problem 2.If I attempt to EXEC the descent early the aircraft descends too quickly. At first it establishes a descent at 1200fpm as expected but after approx 1 minute it pitches down to try and maintain the MACH/IAS at IDLE which prevents it from reaching the IDLE profile. The other day I descended with a 50kt head wind (entered into the descent forecast) and the aircraft failed to reached the idle profile?

[Peer 0]

Hi Do you know the famous B747 Type Rating Course ?Lesson 4 is describing LNAV - VNAV procedures.Check it out and you will learn all about it!http://www.precisionmanuals.com/html/downloads/docs.htmenjoy the B747, Peer

[Guest Totalbeginner]

>Hi> >Do you know the famous B747 Type Rating Course ?>Lesson 4 is describing LNAV - VNAV procedures.>Check it out and you will learn all about it!>>http://www.precisionmanuals.com/html/downloads/docs.htm>>enjoy the B747, PeerI know how the aircraft should perform. What I need to know is if I'm the only one having this problem, or is it a known issue?