Eh? Help with FMC DES procedure, please !

[JSACKS 0]

I am new to PMDG and just finished studying the FMC manual for the -600 model. I understand much of it quite well as I spent 2 years flying the PSS 777 and 744 models. But I am unclear about FMC DES procedure with the PMDG -600 model right now because I think it differs slightly from the 744.In the 744, you dial in your desired descent ALT in the MCP window at any time while cruising and at the programmed ToD, the FMC commands the descent to start when you hit the ToD. But it seems that this procedure is not the same in the FMC for the PMDG 737. My reading suggests that if you dial in the lower ALT within a 50nm range of the ToD in the 737 that the FMC will start to descend you early at 1000 fpm until you intercept the FMC programmed descent path.If I am MORE than 50 nm away from the ToD and have a lower ALT dialed into the MCP, the descent will be started right away to that new lower ALT.Is this correct? And if so, how do you program the FMC/MCP to start decsending you at the ToD using the PMDG FMC ? I am unclear about this.Appreciate guidance/clarification on this item, thanks!JS

[Guest OneTinSoldier]

Hello Jack,You won't start Descending until the ToD unless you go to the DES page and click on the LSK for 'DES NOW'. If you do so, then the plane will start a shallow descent (1000 fpm) until you reach the ToD. Once you reach the ToD then it will go into the calculated descent profile.In other words, if yo don't press 'DES NOW' then the descent will be just like you are used to in the 744.Hope that helps,Jim

[JSACKS 0]

Jim:Hey, good news! Thanks for the reply. I can breathe easier now.Jonathan

[crvm 0]

The procedure works a bit like this,1] Set a lower than current desired altitude in the MCP altitude window prior to descent. The FMC will remind you @ 5 miles of TOD to reset it if you have not. Even if you went a "bit" passed TOD you could still resume descent.2] The default descent mode is VNAV PATH. You can keep your desired target speed by selecting VNAV SPEED DESCENT over PATH prior to descent OR during descent. In PATH mode, manually increse-decrease speed to keep the target by selection of SPEEDBRAKES or increasing throttle by holding down F4 as PATH is keeping path and not speed, at times you can overspeed or slow although if it slos too much the throttles will kick in on their own. 3] As was already mentioned you can hit DES NOW which will start a 1000 FPM descent untill encountering the original descent path thence resume at programed descent profile.4] The aircraft will level off to whatever you have set on the MCP, if you need to stay at a certain altitude till cleared, simplt reset the MCP and re-engage VNAV. If you wait too long you might need to go LVL CHG or V/S to get back within VNAV criteria. Best Wishes,[h4]Randy J. Smith[/h4][h3]P M D G's 747-400[/h3][h4]coming to a runway near you[/h4][/font color]Caution! Not a real pilot, but do play one on TV ;-)AMD 64 3200+ | ASUS KV8 DELUXE | GFORCE 5700 ULTRA @535/1000 | Maxtor 6Y080M0 SATA 80 GIG | 512 DDR 400 | Windows Xp Pro | Windows Xp Pro 64 |