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KingCat

MCP IAS "jumping" up

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Hi,I don't know if this issue is standard behaviour of the 737 or not, so I'll give a detailed description of the problem.This issue only happens on the 737, and not on the 747 (FS2004).Prior to takeoff I select 250 kts. in the MCP IAS window. I have the autothrottle armed, and the flightdirector switch on. Then I start the takeoff roll, and engage TO/GA when the engines have spooled up to 70% N1. After takeoff when "ARM" is displayed aprox. 1.000ft AGL, I press VERTICAL SPEED to set +1.500. Then the MCP IAS "jumps" up with 20 kts. (in this example to 270 kts.) I'm not engaging the autopilot because I'm flying the airplane manually (only VERTICAL SPEED is pressed).However, if I don't use the TO/GA switch, and activate VERTICAL SPEED aprox. 1.000ft AGL, then the MCP IAS does NOT jump up with 20 kts. So there must be a reason why this "jumping" of the MCP IAS only happens when using the TO/GA switch. Is this normal? This behaviour does not happen on the 747.Jon

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I dont fly the 737 but if it's anything like the 747 you shouldn't be putting 250 knots in the speed window. It should be your VREF or VR speed.Rob

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I know that you normally select V2+10 in the MCP IAS window. But that's beside the point right now.I would like to know if this "jumping up" is normal behaviour for some reason or not.Jon

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Jon,AFAIK for the NG you are supposed to put V2 in the MCP speed window if anything. The 20 knot 'jump' you see when using TO/GA is the AFDS adding 20 knots to V2 as it is designed to do. If not using TOGA you could very well enter V2+20 in the MCP.Hope it helps,

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That's correct, you put V2 in the MCP speed window prior to takeoff. Then when you engage CMD A the MCP IAS speed window will jump to V2+20 for initial climbout speed.

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>Jon,>>AFAIK for the NG you are supposed to put V2 in the MCP speed>window if anything. The 20 knot 'jump' you see when using>TO/GA is the AFDS adding 20 knots to V2 as it is designed to>do. If not using TOGA you could very well enter V2+20 in the>MCP.>>Hope it helps,Ok. So this "jumping" is normal. Then I have only 1 question left.Why does this "jumping" only happen on the 737? When I use the same procedure on the 747, then the MCP IAS does not "jump up" with 20 kts.Jon

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Jon, I think you need to read the documentation that comes with these aircraft. The MCP speed window is blank (Edit - above 400FT) with VNAV selected unless you push speed intervene and enter the speeds yourselef just like the real 747. If flying with VNAV engaged speed automaticly increases with flap retraction.If vnav IS NOT engaged the PNF should adjust the MCP speeds.Flaps up you should maintain VREF 30 + 100 knotsFlaps 1 VREF 30 + 60 knotsFlaps 5 VREF 30 + 40 knots Flaps 10 VREF 30 + 20 knots Flaps 20 VREF 30 + 10 knots Rob

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>>Why does this "jumping" only happen on the 737? When I use the>same procedure on the 747, then the MCP IAS does not "jump up">with 20 kts.>>>JonBecause they're two different aircraft and don't share all the idiosyncrasies in operation or computer logic.

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Someone was asking in another forum what is the proper technique for a take off in a 737-300 and although my time is in the NGs i made a post that might have helped him out. Since we are now talking about NGs I will just cut and paste my post:On take off, have the speed set for V2 and set HDG SEL. After you select TOGA and get going we usually select the autopilot on at 500 feet in which the autopilot maintains a TOGA N1 and a speed as decribed by Mats. At 1500 Above Airport elevation the autopilot switches to a Climb Thrust, Level Change mode. We would see a N1-HDG SEL-MCP SPD on the flight mode annunciator on the PFD display. Dont use VS on take off. Heck I use VS about 2% of the time. VS is really used for small altitude changes really. Other than that the preferred method is Level Change or VNAV. Now for a proper take off which i am sure most people dont use on FS, the most common noise abatement procedure is the VNAP B (vertical noise abatement procedure). After take off, climb at the flight director commanded pitch to 1000 feet above airport elevation. We have a white line on the altitude tape that extends up to 1000 AAE on the NG. At 1000 AAE, set the speed on the MCP to UP (cant remember if the classic series has this on the speed tape but it is the flaps up maneuvering speed. Let the aircraft accelerate to the flaps up speed and retract flaps on schedule. Once the flaps are up, make sure the FMA has N1-HDG SEL-MCP SPD annunciated. Keep climbing to 3000 AAE elevation and voila, you just did a VNAP B. The pilot not flying usually does the after take off checks just after the FMA has been checked for the annuciation. hope this helps a bit.

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Hi thereThank you for the information on how to do things properly. For my two pennyworth, I appreciate this type of post because I now know what I should be doing and can now practice trying to get it right as the professionals do. Probably the reason I as a flight simmer do not do a noise abatement take off is that I did not know the procedures in the first place, but I do now, so lots of hard work to do to get this right as well. Now what would be brilliant is if you could find enough time to post something similar on a proper descent and what modes you use, as my boeing won't descent and slow down at the same time (as advertised) so whould love to know how the pros do it, then would have a proper model to try and learn and follow. So please keep these valuable sources coming and teach us armchair pilots how to do it right.best regardsJohn Calleja(BAW352)

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Hey John. I understand people do not realize what the VNAPs are. I would be like "a VNAP what?" as well. The descent part is no magic. I think if you are having problems it usually is programming in the VNAV portion of things. Seems like it is one of the most common problems out there. BUT in the real thing we do use the speedbrake occasionally because the aircraft isnt slowing down to well. Sometimes the winds are a problem. In the real NG we have descent wind forecast which I dont believe the PMDG has. If the winds for CRUISE are programmed as being behind us at 100 kts at 30000 ft the FMS assumes the decrease in winds as you go down will be linear. So the winds at 20000 ft will be 66 kts and at 10000 feet will be 33 kts. So what happens if this isnt the real case. What happens if the winds are actually 80 kts at 10000 feet. Well the FMC has a 50 kt stonger tailwind then expected and this could throw off you descent profile and screw up your VNAV. SO we have the Descent winds forcast where we can input the winds at particular altitudes (dispatch gives us these) so the FMC can take this into account and maintain a nice vertical profile. So that could be problem 1 why you are not getting a good profile. But as you may or may not know there are some companies that cant program the VNAV portion in the software if their lives depended on it. I wont get into that. But PMDG does a very good job from what I have seen. Keep in mind to how old the PMDG 737 is. It amazes me how widely used this plane is with respect to how old it is. Everybody has this plane. A lot of people ask me how much I lke this plane and I make the comment of it being a very nice plane still. Then I think about when it first came out (I think about 5 years ago) and realize how amazing this plane must have been back then. I didnt fly the NG back then so I would know how to rate it. It sure will be nice to see PMDG come out with the new 737. HINT HINT Robert!

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Jack,Nice to see some real world comments like this. The PMDG NG has the FORECAST page fully operational but the problem most people seem to have is getting the actual wind data. FS own weather will not easily supply this. I use Active Sky which prints out a nice summary of all winds at different altitudes for all route waypoints. This I use for the DES FORECAST.Cheers,

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Yeah I use Activesky too and does a nice job giving the winds. See? The PMDG ws ahead of its time if it has the descent forecast winds 5 years ago!

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