Descent Phase - What Am I doing Wrong Part II - 747

[johndrago 4]

I understand that if I change the altitude on the MCP while in VNAV cruise, the plane will start it's descent to the new altitude at the TOD.However...Since I'm using FS ATC, they usually start my descent 50 miles before TOD. What I do now is dial the new altitude in the MCP, and click the center of the ALT knob to start the VNAV descent. What I'm finding is that the engines retard quickly, and when the 747 starts it's descent, it begins very steeply to makeup for the speed it's trying to catch up to (like FLCHG).What's the proper procedure to initiate a VNAV descent when starting before the TOD?Thanks in advance,John

[Guest Just747-400]

John,You

[johndrago 4]

>John,>>You

[crvm 0]

Use the DES NOW function on VNAV pg 2. What you are doing there by using alt int is trying to lower your crz altitude since that will set the MCP altitude as the crz altitude-something you cannot do in CRZ without starting an early descent (true you are wanting to descend but this is not the procedure to accomplish this). You can also perfrom a " ACT CRZ DESCENT" which instead of using the ALT INT procedure (Pressing the ALT KNOB after resetting the MCP alt), simply reset the MCP alt and type a lower than current crz altitude into the FMC crz alt line (LSK1) and hit EXECU. You will still retain your crz phase this way. Of course you can go FLCH/V/S too (V/S perferred)... [h4]Randy J. Smith[/h4]AMD 64 4000+|ASUS K8V DELUXE|SAPPHIRE ATI X800XT PE|MUNCHKIN 3200|80 gig SATA|DELL 1905FP 19" LCD|TRACKir PRO|PFC JEPPESEN MOONEY YOKE|CH PRO PEDALS|

[Guest Just747-400]

Randy,What is he doing is an early descend, if you within 50 nm of td and dial a clearance alt and press the altitude knob you should get 1250 fpm until reaching new td or new target altitude. Sorry, but vs is not the preferred method, actually many airlines teach pilots to stay out off vs as much as possible because of the potential problems involved with it. Just only 2 very important I can think off: no stall protection, no speed protection.

[crvm 0]

Hey Alex, I think we are not talking about the same thought here since I was referfing to the initial descent, in other words how we get to the descent phase. If he desires an "early descent" is there somewhere that states the one method is by using ALT INT to begin the descent? I know you can use it foe descents ;P. If you use ALT INT are you not stating a restrictive altitude to descend too? Plus is not DES NOW less workload than ALT INT? Des NOW removes restraints whereas you must push the alt button more than once etc. My responce was to use what Boeing states to use for an early descent, namely using DES NOW through the FMC prompt and not pushing the ALT INT button for DES NOW but hey you fly the thing :(.The way I read it, the "descend now" from using ALT INT is a result not a means of initiating an early descent inavertantly using ALT INT while in crz - lowering one's crz altitude which you cannot "achieve" with ALT INT. [h4]Randy J. Smith[/h4]AMD 64 4000+|ASUS K8V DELUXE|SAPPHIRE ATI X800XT PE|MUNCHKIN 3200|80 gig SATA|DELL 1905FP 19" LCD|TRACKir PRO|PFC JEPPESEN MOONEY YOKE|CH PRO PEDALS|