The 737 NG FMC takes me down always too late !!

[Guest carlonch]

Hi everyone:This is my first e-mail in this forum so I want to say Hello to all the people here. I love the PMDG 737 NG, as a fact, the more I fly it the more I like it. I found the Timothy Metzinger

[Guest tmetzinger]

Are you using any weather add-ons? If you have a tailwind that you haven't told the FMC about using the CRZ WND in the PERF page, or the FORECAST in the DES page, then it will be hard to follow the path on descent and you'll overspeeed.When you get the "DRAG REQUIRED" notice you should put out the speedbrakes, that will help keep your speed down.

[Guest carlonch]

Hi Timothy:Looking forward for the V3 version of your Advanced Operations Tutorial. V2 is great. I still have to complete the 3rd tutorial.Though I

[Guest glenb]

CarlosThis is a common thread. Descends using the FMC often result in high speed and steep descends. I have noticed that the problem occurs when there are constraints in the log page that have an altitude constraint of

[Guest tomahawk_pa38]

Carlos,You will find lots of threads on this here in the forum. My advice - increase your descent speed to /300 on the descents page of the FMC and keep your eye on your speed. The minute it start to creep above 300 kts - get the speed brakes out. Don't be afraid to put them back down again if the speed drops too far and then raise them if it starts going back up again.

[Guest carlonch]

Thanks for the advices.Tonight I tried a mixed technique. I climbed up with the FMC (VNAV and LNAV activated) then fooling around with the Flight Plan Modifications (Intercept course, adding and deleting fixes, etc). For the descend I leave the FMC do its thing, but at 80 miles I prefer to use the LVL CHG and play with the speed to get at 240 knots, 3000 over the airport altitude at 20 miles of the runway. Looking for the localizer and the glideslope from there with VOR-LOC activated. It worked fine so far...

[Guest tmetzinger]

>Thanks for the advices.>>Tonight I tried a mixed technique. I climbed up with the FMC>(VNAV and LNAV activated) then fooling around with the Flight>Plan Modifications (Intercept course, adding and deleting>fixes, etc). For the descend I leave the FMC do its thing, but>at 80 miles I prefer to use the LVL CHG and play with the>speed to get at 240 knots, 3000 over the airport altitude at>20 miles of the runway. Looking for the localizer and the>glideslope from there with VOR-LOC activated. It worked fine>so far... Not a bad technique, and similar to what is used by lots of airlines, although they tend to use VS in descents because a constant descent rate (with fluctuating airspeed) is easier on the "cattle" in the back than a constant airspeed descent (with fluctuating VS).Also, if you want a decent approximation of a three-degree descent slope (typical for ILS), you can use the rule of thumb to be about 3000' AFE (above field elevation) for every 10 NM from the airport.So at 20 NM you'd want to be somewhere around 6000' AFE. Flying lower for longer distances burns more fuel, and annoys more neighbors with noise (not much noise at 3000, I agree).

[Guest jacaru]

I have found some strange behaviours in VNAV that i dont really know if they are correct or not (different of the known VNAV bug with constraints). Sometimes in VNAV PATH I start to slowly overspeed when the plane still has enough margin to correct. For example I overspeed but the throttles are not idle? When the plane asks me for drag i would in return ask him to please try to reduce power first. FMA says ARM for autothrottle in this circumstances. I dont know what prevents the aircraft to reduce throttle and VNAV SPD does the trick but then what to use VNAV PATH for. Other times is just late in following the path and then a greater down path angle is required to recover.Winds and expected speed reductions are good data to provide to the computer besides altitude restrictions. The key thing is always anticipate what the plane will do and monitor what it really does. In VNAV this is the hardest thing for me since many times it does not do what i expect (or what i would do if i was VNAV myself). Need more practice and experience with the plane i guess.In any case many times i am not comfortable with what VNAV does. I use LVL CHG for fast descends and V/S otherwise. Passengers and myself feel more comfortable with constant descent rates.Jaime.

[Guest navneet_cxp]

Hi guys,Regarding the descent......what i do is a managed descent,that way you can start your descent late and also manage your speed.Say you are 100 nms from your destination VOR and at FL210(lets assume).The FMC will start the descent at around 70 miles and start reducing speed.But in managed what i do is start my descent at 60 miles and descend at 320kts this way i get a steeper descent profile and reach my destination a little faster.Well thats how i do it.But i make sure i reduce my speed to 250 kts when i reach 10000feet.,and maintain 250 kts till about 12 dme from the station and then start the approach procedures.Enjoy and Happy Descending....!!!-NavneetFS 2004 Version 9.1AMD Athlon 64 3000+ATI Radeon 9600 128MB - Anti-Aliasing 6x512MB DDR400 Kingston RAMWestern Digital 30 GB - Seagate 8.4 GBHp CD12 CDRW - Pioneer DVD ROMLG Flatron 775FT 17' MonitorCreative SBLive! X-Gamer 5.1Creative Inspire 5.1 5200Windows XP Pro SP2 v.2180Microsoft Sidewinder Precision Pro 2Logitech Cordless Optical Mousehttp://www.hifisim.com/images/as2004proudsupporter.jpghttp://www.avsim.com/pss/phoenix.jpghttp://www.precisionmanuals.com/images/forum/747400.jpg-|http://www.precisionmanuals.com|-