After takeoff problem.

[Guest D17S]

Hi Ted, I'm new to the 737. So, on the 737, the TO mode is "SPD?" Is that a pitch mode (right FMA). I haven't heard of that before. Maybe it's a thrust mode (left FMA)? Don't know 'bout the '37. Also, if an MCP setting of V2 is initially set, engaging the AP will drive that setting to V2+10? The AP will then control to that. Is that still using this right FMA (pitch) "SPD" mode?Then at 1000 feet, when I engage Vnav, the right FMA goes from "SPD" to VNAV"? Will my target airspeed change again? Thanks,

[Guest 9946578123]

Hi Ted I tried but it just won't work.I've tried more than 10 times with different solutions from you guys but it still went thesame.Its looking like the A/P losses control of the trims.When I activate autopilot it trims nose up to 30

[downscc 1,327]

The only condition where I can duplicate your problem is when, for whatever reason, the airspeed gets too low. My gut reaction to low airspeed after takeoff is to lower the nose but the AP raises the nose like a novice trying to increase the climb... don't know why she does that but maybe this is a clue to your problem. Earlier you said you observed that after rotating to 8 deg nose up engaging CMD raised the nose to 15 deg... what does the airspeed do? It should be either maintaining V2+something or increasing. Is it decreasing?

[Guest 9946578123]

Dan,With 15

[Guest Hawkeyeted]

>Hi Ted, >>I'm new to the 737. So, on the 737, the TO mode is "SPD?" Is>that a pitch mode (right FMA). I haven't heard of that>before. Maybe it's a thrust mode (left FMA)? Don't know 'bout>the '37.Sam, you are correct, it is a thrust mode, but speed limited based on flap settings. The aircraft is smart enough to not overspeed the flaps. >Also, if an MCP setting of V2 is initially set, engaging the>AP will drive that setting to V2+10? The AP will then control>to that. Is that still using this right FMA (pitch) "SPD">mode?Yes, it does bug-up for you. Again, in a thrust climb, when V2+10 is reached, the aircraft will pitch to maintain that setting. This isn't really any different than the PMDG 744. I just can't recal if the 744 will bug-up since you can arm VNAV/LNAV prior to T/O. >>Then at 1000 feet, when I engage Vnav, the right FMA goes from>"SPD" to VNAV"? Will my target airspeed change again?It will go from "N1" to "VNAV SPD", and yes it will then bug-up based on FMC calculations, but limited by flap speed setting.

[Guest Hawkeyeted]

>Hi Ted I tried but it just won't work.>I've tried more than 10 times with different solutions from>you guys but it still went thesame.>Its looking like the A/P losses control of the trims.>When I activate autopilot it trims nose up to 30

[Guest Hawkeyeted]

>Sorry for the VNAV actualy it needed to be LNAV.>>...TotoErr....you can't arm LNAV either....

[downscc 1,327]

Ted I agree, unless Toto has manually put that much trim in but I think everyone would have zero'd in on that earlier. I need to start a separate thread to ask about FSUIPC and it's utility with PMDG, if any.

[AWACS 12]

Off-topic, but I couldn't help but notice that your username is the same amount of digits as a phone number, so I just wanted to say that if you did use your phone number as your username you should probably change it to protect your privacy.Jeff

[Guest 9946578123]

Actually the autopilot can trim the aircraft but right after I turn on the CMD1 or 2 it trims the nose to get up very fast and that's what get's out of control; when I trim the aircraft back down A/P trims it up again to about 40

[Guest D17S]

Check the airplane's loading again. There will be a CG figure somewhere on one of the FMC setup pages."Not too high or too low" I'm guess this means that you are hand flying the airplane right after takeoff. You are also maintaining around V2+10 by: 1) Leaving the thrust at Takeoff power and 2) Controlling airspeed by pitching the nose up or down as necessary to control and maintain airspeed at around V2+10.Is this right? If so, that's terrific. You're doing it just right. Now try to give a more specific description. Here's the way to think about what's going on. Try to answer these questions for us. It will help you (and us!) understand more clearly what's going on. Tell us: What is your TO weight and Center of Gravity? Where is trim set.What are your Vspeeds? What is your TO flap setting? What is your TO thrust? What pitch are you flying to maintain your initial climb airspeed?What is this airspeed?What modes are the FMA annunciating (all three)? Watch these carefully. They can change as the takeoff progresses.How many degrees of pitch is the pitch command bar suggesting (in the PFD)?Where is this relative to the airplane symbol? When you engage the AP, do the FMA's change or stay the same? (What did I forget guys)Now test fly again . . but this time turn MSFS's speed down to 1/4 speed so you can see what's going on. Use "pause" constantly. Get out a pad and take notes. Have fun. This is really great stuff. You're a test pilot!

[Guest Hawkeyeted]

>Actually the autopilot can trim the aircraft but right after>I turn on the CMD1 or 2 it trims the nose to get up very fast>and that's what get's out of control; when I trim the aircraft>back down A/P trims it up again to about 40

[downscc 1,327]

Confirm gear up after rotation.What is the airpeed and trend (increasing/decreasing).That's all I caught, you're pretty good Sam.

[Guest Hawkeyeted]

Another thought regarding FSUIPC: What version do you have? This sounds like an issue that existed with an older version (3.4 maybe?) Current should be v3.53.

[Guest D17S]

Another thing we need to keep in mind is that the automatic system that drives stab trim only wants to maintain the current pitch attitude. You can manually do it for sure, but the automatics that drive trim won't change the pitch of the airplane (on purpose anyway). The AP uses the elevator to facilitate a pitch change, not the stabilizer. The job of the automatics that drive the stab trim is to "chase" the current elevator position. Autostab trim's goal is to fair the elevator-horizontal stabilizer assembly to provide aerodynamic efficiency. The AP drives the elevator to change or control pitch and the auto stab trim system just follows along. The point is this. If we see that the Flight Director (i.e., the AP's commander) is accurately suggesting pitch, this pitch will become a direct order to the AP (command) once the AP is engaged. Just like the pilot CAN if he chooses, the AP now WILL command the elevator to fly the airplane to the Flight Director's suggested pitch. If the stab trim was way out of position to start with, once the AP is engaged the stab will start to trim to fair the elevator. Depending on how far the stab was out of position to begin with, this could take some time. As the stab drives, the AP will continue to use the elevator to maintain the Flight Director's suggested pitch. So we can have the stab driving one way and the elevator bobbing around trying to maintain pitch as the stab drives into position. This might cause an upset. But if you can hang on long enough, the AP/Autostab trim team will sort it out. (The real trick is to have the stabilizer set about right before TO!) If the stab is driving and the elevator cannot maintain the Flight Directed pitch, it is likely there is something exterior to the model that is causing the stab to drive. That