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Level Change

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Hello,...I am new to owning the PMDG 737 and was wondering what the level change does...I looked in to it trying to find some information about what it is used for and can't find any that will tell me...if someone knows could you tell me....?thank youChad Moore

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Hi Chad,Take a look a page 7-18 of the PMDG 737 Aircraft Systems and Cockpit Overview chapter of the PMDG 737NG flight manual. Lots of great information there about the autopilot and its functions."The LVL CHG mode coordinates pitch and thrust commands to make aautomatic climbs and descents to preselected altitudes at selected airspeeds"Best,Vin ScimonePMDGwww.precisionmanuals.comhttp://www.precisionmanuals.com/images/forum/devteam.jpg

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Other words, it will use the altitude you enter and speed to maintain that speed WHILE going to the altitude you selected. Bit confusing, but it's more like an automatic V/S selector that will go up or down to slow or go faster.Nick B.Continental Airlines Virtual 737NG Pilothttp://www.precisionmanuals.com/images/forum/800driver.jpg--AMD Athlon XP 3200+ @ 2.2 Ghz (Equal to 2.8 ghz)400W Power supply3x 80 mm Case FansSoyo VIA KT600 Dragon PlusnVidia GeForce FX 5200 128 mb2 x 512 PC400100 GB Western DigitalMicrosoft Sidewinder Precision 2

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LVL CHG is as people have already pointed out, a climb / descent mode but in actual fact it is pretty simple to understand when put in laymans terms which I will try to do here:In a climb with LVL CHG mode:The A/TRH moves the thrust to CLB (Climb power) as decided by the N1 limit computer. The Auto pilot then pitches the aircraft in order to maintain the speed that you have set in the window. If the speed starts to reduce it will lower the nose until it starts to recover and then return to it's best climb attitude. If speed starts to increase then it will raise the nose slightly till the speed starts to drop off and then re-adjust its attitude. Put simply it maintains the speed in the window and varies the rate of climb/descent to maintain the speed.In a descent with LVL CHG mode:The A/THR goes to RETARD ie. it retards the thrust levers to idle and then pitches for the speed as in the above passage. LVL CHG is used primarily because it provides speed protection particularly in the climb. If you use V/S mode in the climb the A/THR will adjust to maintain the speed up to its maximum climb thrust. If you set 6000fpm in the V/S window the nose will pitch to maintain the 6000fpm. Inevitably the thrust will not be enough to maintainthe climb rate and the speed will start to drop off and will continue to do so till you reach the stall. Your only protection is a safety mode in the Auto flight system which in theory will not allow the speed to go all the way to the stall but I wouldn't want to try that out in real life.So put simply in the climb LVL CHG goes full climb power then pitches to maintain the desired speed. In the descent LVL CHG retards the power levers to idle and pitches for speed.For those of you familiar with turboprop autopilots with an IAS mode the LVL CHG mode is very similar to this!Hope that helpsKris

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Kris HeslopNow that's an answer! Thanks for posting that information.I now understand LvL Chg as well. Many thanks.Waldo

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