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scanham

Level Change question

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I am new to this aircraft - I am flying the 737-700 (SU2) on FS9. This is real basic question but I am a little confused. I want to change altitudes, say from 5,000 to 8,000. I'm climbing through 5,000 and I dial in 8,000 and click Lvl Chg. Is this the same as the FLCH mode on PIC 757, which I believe controls speed as well as VS. Or, am I suppose to dial in the VS? Is there a good place to learn MCP basics? What is the best way to control the aircraft up to flight level aside from uning VNAV. Thanks, Steve Canham

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Hi Steve, If my memory serves me right, LVL CHG, and its counterpart in the 757/767, will command VS to achieve the speed dialed in the MCP. This means that your airspeed is the primary parameter when using this mode. You will notice the effect if on approach and you dial in a lower altitude and a lower speed at the same time: The a/c will first pitch a bit up to loose the airspeed and then it will go for the altitude change.Hope this helps,Boaz

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"Is this the same as the FLCH mode on PIC 757, which I believe controls speed as well as VS. Or, am I suppose to dial in the VS?"Although I'm not familiar with "PIC 757", the two modes are roughly the same on the 737NG and the 747-400/757/767.FLCH comes in various degrees of intelligence. On the more intelligent types, for small altitude changes, the A/T will provide only enough thrust to achieve the target altitude within a certain time frame (from memory, 120 seconds). The precise thrust to achieve the target altitude in this time frame is computed when you push the FLCH button. The elevators then hold the aircraft to a certain airspeed (current airspeed or MCP speed). If atmospheric conditions change as the aircraft climbs, the autothrottle may increase the thrust to help it achieve the altitude target within the set timeframe. If the aircraft looks like it will achieve the target altitude too early, however, it will not reduce the thrust. For large alitude changes, the thrust will usually go to the current thrust reference limit.At this point, however, I'm not sure if the 737NG "LVL CHG" is as sophisticated as FLCH on other Boeings.Interestingly, I read, the 737NG A/P will default to LVL CHG if in V/S and the aircraft cannot achieve the MCP target airspeed (not sure if this is modelled in PMDG tho').Hope this helps.Cheers.Ian.

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Thanks to both of you for helping me better understand all of this. I took some time to read more of the manual and your help has thrown additional light on it for me. Looking forward to more practice this weekend. What a great aircraft - well worth the money. Happy New Year! Steve Canham

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Actually, Ian,LVL CHG in the 737 is very crude (actually, the whole autopilot is very crude). That's why LVL CHG is not really to be used for small altitude changes because it will attempt to go to full CLB N1 for a climb or IDLE for a descent, instead of using a logical amount to reach the new altitude smoothly instead of like a rocket or a brick. For smaller alt changes, V/S is used, as a sort of make-shift altitude change method. On 757/767/747/777 the FL CH is all you have to press to change altitude smoothly.Same goes for all the other autopilot modes. A heading change of 15 degrees in HDG SEL is done at 25-30 degrees of bank, even at cruise speed and altitude. Not comfortable at all. The 737NG does have speed protection in the V/S mode where it reverts to LVL CHG, where the 757/767/747 (don't know about the 777) do not, which is again related to the fact that V/S mode is rarely needed on those aircraft.

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"Actually, Ian,LVL CHG in the 737 is very crude (actually, the whole autopilot is very crude). "Hence my remarks...."Roughly the same"... and "At this point, however, I'm not sure if the 737NG "LVL CHG" is as sophisticated as FLCH on other Boeings." ;-)I suppose it's roughly the same for large altitude changes (full thrust going up or idle going down).Anyway, thanks for the tips, Iz :-)Cheers.Ian.

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Hi IZWell as far as i can read you seem to be a RWP ( Real World Pilot), and can you tell me what the bank angle knob should be set to on the PMDG737NG for different speeds and degrees of turn. I have mine one notch down from 30 (25??) no matter what speed or how many degrees of turn i need to make....So what's the rule of thumb on this one ?Thanks

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BTW, Iz, can you adjust the rate of descent in LVL CHG (on the NG) by manually adjusting the throttles? This is a handy feature on the 767 and 747-400, I recall.Thanks.Cheers.Ian.

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Hallo Pieter,Well, usually the bank angle limiter is indeed at 25 degrees at our airline, but LNAV or VOR/LOC capturing completely ignore the bank angle limiting setting.Iz

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