Hello,I have a question about LVLCHG.When I'm at 6000ft at 240 kts, (with VNAV mode) I enter 3000 ft in the Altitude window, and 200 kts in the speed window and then I push LVL CHG. The aircraft raise the noise and stop its descentand but time that speed falls I

Im not sure exactly what you mean here. If your talking about decending with VNav engaged then you probably want the FMC to handle it for you. I dont use level change to decend in preperation to land or decend to an altitude to capture the glideslope. If you look at you course line in you display you will see a TOC (Top Of Climb)in small text on the display. At a point when the FMC calculates it's time to decend you will see TOD (Top Of Decent) "AFTER" you reach TOC you can run the MCP altitude to 00000 the plane will fly along at whatever altitude the FMC/VNav is setup for. When the nose of the triangle (your plane on the display) reaches TOD it will start to decend all by itself. I generally run the MCP altitude down to the decision or runway altitude, before I get to TOD thats because I never crash...yha right! If your IFR and a controller gives you heading and altitude changes that deviate from your flight plan setup in the FMC,then I use level change. him and what you have setup in the FMC may not agree, if you know what I mean.You will allso notice two little green circles tha denote the demarcation of the speed restriction (250 knts) below 10,000 feet.Regards

Hey Autothrottle,First off, you should sign with your real name in this forum, it's the rules :)Now to your question: If you're using level change then you generally disregard the vertical descent plan profile (i.e. the pink dot will be low). When you enter a number in the speed window, in your case 200, the plane will level out and then apply idle thrust until it gets to the set speed. As you have noted this level period will put you out of the descent profile, and there is nothing you can do about that. You can however limit the amount of deviation by reducing your speed quicker. To do that all you have to do is extend the speed brakes.You can also use the speed brakes to make a faster descent. If you leave them out the autopilot will make a steeper dive so that the airspeed remains the same.If you want to keep the plane on the descent plan you should use VNAV. However you will still get the same problem when you reduce speed although this time, once the new speed has been met, the autopilot will correct for the vertical deviation itself.I hope this helps :)CheersDavid

Hi,You have to understand LVL CHG, basically it will try to keep speed by using pitch. If you are dialing in a speed that is lower than your current speed and engage LVL CHG, the A/P will try to reduce speed by pitching up, thus climbing. And vice versa. When in level flight and want to descent with LVL CHG, you should not lower the speed. The trick is to start to decrease the MCP altitude and engage LVL CHG. (By the way. If you go from VNAV to LVL CHG there's no way you can change speed, that window is closed in VNAV). If you lower your MCP altitude and engage LVL CHG from VNAV the MCP speed window will open and you can start fiddeling with speeds after the descent is stabilized.Hope it helps,

>Hi,>>You have to understand LVL CHG, basically it will try to keep>speed by using pitch. If you are dialing in a speed that is>lower than your current speed and engage LVL CHG, the>A/P will try to reduce speed by pitching up, thus climbing.>And vice versa. >>When in level flight and want to descent with LVL CHG, you>should not lower the speed. The trick is to start to decrease>the MCP altitude and engage LVL CHG. (By the way. If you go>from VNAV to LVL CHG there's no way you can change speed, that>window is closed in VNAV). If you lower your MCP altitude and>engage LVL CHG from VNAV the MCP speed window will open and>you can start fiddeling with speeds after the descent is>stabilized.>>Hope it helps,That's a good way - go down first and THEN slow down.There's another alternative, use VS and dial in the appropriate amount of vertical speed to stay on the profile, and then set the speed in the MCP window.What will happen is the airplane will use pitch to maintain the VS (descent profile) and then will attempt to use the throttle to obtain the MCP speed.The key difference is that in LVL CHG, speed has priority. in VS, the vertical profile you set has priority.

>>Hi,>>>>You have to understand LVL CHG, basically it will try to>keep>>speed by using pitch. If you are dialing in a speed that is>>lower than your current speed and engage LVL CHG, the>>A/P will try to reduce speed by pitching up, thus climbing.>>And vice versa. >>>>When in level flight and want to descent with LVL CHG, you>>should not lower the speed. The trick is to start to>decrease>>the MCP altitude and engage LVL CHG. (By the way. If you go>>from VNAV to LVL CHG there's no way you can change speed,>that>>window is closed in VNAV). If you lower your MCP altitude>and>>engage LVL CHG from VNAV the MCP speed window will open and>>you can start fiddeling with speeds after the descent is>>stabilized.>>>>Hope it helps,>That's a good way - go down first and THEN slow down.>>There's another alternative, use VS and dial in the>appropriate amount of vertical speed to stay on the profile,>and then set the speed in the MCP window.>>What will happen is the airplane will use pitch to maintain>the VS (descent profile) and then will attempt to use the>throttle to obtain the MCP speed.>>The key difference is that in LVL CHG, speed has priority. in>VS, the vertical profile you set has priority. Mat's is right on about LVL CH pitching to slow. One other note here is that one should not use LVL CH under 10000, not that one can't just that I don't know any who do. LVL CH is better used for large altitude changes for various reasons. Tim is also correct that V/S is the way to go to keep the correct descent profile (remember 3 degrees descent profile?). So, *generally* for any altitude change 1000' or more go LVL CH and V/S for smaller changes. Of course one can use V/S for larger altitude changes but you must keep a close eye on *speed*...[h4]Best Wishes,Randy J. Smithhttp://www.precisionmanuals.com/images/forum/betaimg.jpg