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henkscheffer

Slow down the aircraft in approach

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How can I slow down the aircraft in approach. I have tried a lot of settings. My FMS tells me that the final must be 160 knots but in real it is 190 knots and that’s too fast. I used my speed brake, bring the speed manually down, have my flaps at 20 etc. But…… always too fast. Sometimes I follow only the FMC but nothing.What am I doing wrong? Thanks in advance Henk Scheffer

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this has been gone over 1000x search the forums theirs mulitple posts and videos on this topic


John C

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from numerous posts, the -800 WL is very slippery. In essence you can either slow down, or go down. Its a energy management problem. During descent you exchange potential energy to kinetic energy (some of which is lost through friction). You might want to descend a little earlier and level off for 5 miles under idle thrust to slow down. A real challenge is to time your descent so that you are on idle thrust (or thereabouts) until glideslope intercept. hope that helps. paul

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start your decent earlier. A simple way to do this (ok, maybe not industry standard but oh well, it works) is : If your at 33000 and you want to be at 3000 at a given piont you would do this 33000ft - 3000ft(altitude you want to be at) = 30000ft x 0.03 = 90. Start your decent 90 NM from where you want to be at 3000. There are some video's here--> http://forum.avsim.net/forum/432-pmdg-737ngx/ regarding decent.

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start your decent earlier. A simple way to do this (ok, maybe not industry standard but oh well, it works) is : If your at 33000 and you want to be at 3000 at a given piont you would do this 33000ft - 3000ft(altitude you want to be at) = 30000ft x 0.03 = 90. Start your decent 90 NM from where you want to be at 3000. There are some video's here--> http://forum.avsim.n...32-pmdg-737ngx/ regarding decent.
I would say that Is industry standard Big%20Grin.gif It looks very complicated how you wrote it though. (Well for me it does Monkey.gif ) Just 3 x your height......25 Thousand = 75NM. Continuously do this sum all the way down to manage your approach. You can -1NM per knot of headwind and +1 NM per knot of tailwind. A few of the 737 Drivers I know just press the meters button because 1 m = 3.281 ft. So you can just read your meters in height for your distance in NM you require. Craig.

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I don't have the NGX yet but on the FS9 version I usually went to the DES page on the FMC and set the speed at say /280 on the target speed by typing in just that (/280) on the scratchpad and then line selecting it for the target speed in the descent. Before it reached TD it would slow down to that speed and then start the descent and largely maintain it all the way down. Gerry

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You may have good use of turns before final to help bleed the energy. Just ask for reduced speed before the turn and the turn itself will help to decelerate. Pierre Laine

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Slowing down works fine flying alone - I just use VNAV all the way down to final. Flying online has been a bit problematic, it seems that VATSIM controllers are used to higher descent / deceleration rates than what you get in the PMDG.

My FMS tells me that the final must be 160 knots but in real it is 190 knots and that’s too fast.
190 knots on final sounds excessive. Where did that number come from?

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the x3 method is pretty good. In fact if you go through the mathematics, then a good rule of thumb is start descent at 3x(the height you want to lose in 1000's of feet)+10nm for slowing down (maybe even 15 for the 800WL) and descend at a rate of 5x your ground speed so descending from FL370-4000' at a GS of 450kts would be... descend at 3x33+10=109nm at a rate of 450*5 (450*10/2) = 2250fpm (or 2300fpm rounding up) this should work pretty well, and its a tip I got from my friend who luckily gets to fly the airbus! paul

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check out the videos on the first page of the forum, really helpful


thank you,Jim

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I even use 4 x times the altitude i need to lose. It allows me a little more time to shallow my descent prior to going below 10,000 for slowing. If you use this technique, just remember well prior to your descent you need to put a descent on request. That's what we do in the real world. On vatsim, let the know you are looking for lower prior to your calculated descent point. Even in the real world we have to query the the controller.

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In the real plane I just level out until I slow to my desired speed and then start descending. I will be above the desired path for a bit but I typically don't have trouble getting back down to it in a timely manner. You can watch your vertical deviation on the VNAV Descent page to see how fast you are get back to the desired path.


Tom Landry

 

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