Difficult to slow down

[WebMaximus 372]

My point was it's not as much of an issue in the real plane. It seems more often than not that I end up adding power during the descent in VNAV.VNAV, LVL CHG, V/S. . . it doesn't matter - they can all achieve the same descent rates. One doesn't magically make the same plane descend at a higher rate.

Wow...adding power during a VNAV descent is not something I'm very familiar with in the NGX :( Haven't had the time to try out using a lower CI yet but will later today and will be very interesting to see the difference!Thanks for participating in these forums Matt and for sharing your knowledge and experience from the real world, much appreciated! Edited February 17, 2012 by WebMaximus

[WebMaximus 372]

If VNAV is correct, all forecasts putted in, there will be no need of using speed brakes as they are a loss of efficiency and is something that the FMC don't want.The NG is slippery, but the NGX with few users suffers about an idle bug, this bug is present below 15500 fts and will lead in an higher idle around 40% of N1.Before someone speaks about the approach idle, I'm speaking of a bug where the idle changes with altitude only, with flaps and gears retracted.However, sometime most users experience that issue if cowl anti ice is on, this is normal as it increases the idle. If you want to use AI you must let the FMC knows in the des forecast so it will change the path to a soft one.

How exactly do I enter this info in the FMC on the DES FORECASTS page? Tried to find some info about this in the documentation but couldn't find it although I'm sure it's in there somewhere...

[simbio 56]

How exactly do I enter this info in the FMC on the DES FORECASTS page?

PMDG-NGX-FCOMv2 page 1084

[davierosoft 13]

Push the DES page, you will find the FORECAST page, push and enter in the forecast page,Put the info you want to put, for anti ice put the altitude you switch it on, and the altitude you will switch it off. The FMC will correct TOD and ramp to adjust it.

[WebMaximus 372]

Thanks guys!

[WebMaximus 372]

Just wanted to let you know descent in VNAV mode works so much better now after all tips provided in this thread! What I've done is:

• use a CI of 7 which I've learned is a realistic CI value when flying SAS 738s
• enter TAI ON/OFF alt in the des forcasts page when in use
• and this is probably what made the biggest difference...using AS 2012 to import the route to be able to again on the des forcasts page enter the wind conditions for 3 different levels

So...for anyone else with similar problems finding themselves to almost always being forced to use the speed brake try this you too!Just noticed this was my 2500'ed post, will that give me a beer :(?

Edited February 21, 2012 by WebMaximus

[maddog83 0]

Ok, but the problem isn't the way of flying using vnav, cost index and etc etc...but the b738 tendency to accelerate with slow rate of descent as well; as i've written some posts above with 250ias, clean configuration, idle(no bug, no anti ice) it can descend with max 1200ft/min otherwise you need to increase the rate using speedbrakes. Consider that a Ryr pilot told me that in the same condition the rate is about 1800/1900.

Edited February 22, 2012 by maddog83

[WebMaximus 372]

Yes, I've noticed this too. I guess I've get used to the 1200-1300 ft descent rate but I've also read real drivers saying they have 1700-1800 in the real bird.Maybe the guys at PMDG could have a second look and see if it could be adjusted? On the other hand I've also read posts where PMDG said the descent rate in the NGX was validated by real drivers and they said all was good...?

[maddog83 0]

I hope PMDG will have a second look to get 738 closer to the real one...

[Jefferson 3]

I would also say.. ALWAYS VERIFY YOUR VERTICAL PROFILE! I mean, don't fully trust the data Navigraph provides on it's Sid/Star database. Sometimes the values of restrictions are wrong. Verify the charts for correct values. Also, always provide the descent info to FMC, via Forecast Page.If you think you'll arrive high and hot 10nm prior to the FAF/OM, go to the Legs page and edit the vertical profile values. Use all your resources to slow it down, I.E Lowering the gear to increase descent rate, open those speed brakes, that's why they are there, to help you slow down. Fly Ahead Of Your Airplane! Plan Ahead! Act Ahead!But the fact that people complains about the Vnav behavior somehow amazes me. Seriously, this is the best VNAV simulation I've ever seen in a payware aircraft. Left alone the first flights, back in august, I don't remember seeing the airplane doing it's math wrong. The Vnav is always spot on. But again, verify you planning, the fmc data. The 738 is slippery, most RW pilots says so. It takes planning to do it right.

Edited February 22, 2012 by Jefferson

[maddog83 0]

I say again: it's not a question of Vnav handling, i'm not talking about the ways to set the vertical profile on FMC, i'm just talking about FLIGHT DYNAMICS...I know the story of 'slippery 738' but not 1200ft like i'm experiencing but 1800 could be a quiter real...

Edited February 22, 2012 by maddog83

[WebMaximus 372]

Of course you're right it's important to plan ahead and use all available tools to help you like using the speedbrakes, the descent forecasts page or even lowering the gear and I'm also with you in the NGX being probably the most impressive and authentic a/c to date in FS but I still hope PMDG will at least have a second look because a difference of about 500 ft / min between the NGX and the real NG is still quite much and it also will make the already slippery -800 even more slippery.

[maddog83 0]

I perfectly agree with you...this is what i meant