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Guest joyschtik

1 1 747400 VNAV anomaly

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Hi all,VNAV does not engage after takeoff even though I've programmed the FMC and have VNAV armed for departure. After takeoff, I tried VNAV, THR or SPD to no avail.It will only engage if the current speed drops 15kts below bug speed.1.What am I not doing right?2.How can I solve this?3.Has anyone experienced the same or similar problems?Thanks

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Would it be possible to post a screenshot of the cockpit at the time you tried to push the CMD button?I assume there are no significant messages on EICAS prior to engagement?Thanks.Q>

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I'm not sure how to do that but I'll try. BTW, what's the connection between the CMD (autopilot I assume) button to VNAV engagement? And, no EICAS msgs either.....WEIRD..Thanks for your help, see if I can get the screen shot..

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"what's the connection between the CMD (autopilot I assume) button to VNAV engagement?"Normally, the VNAV/LNAV buttons are "armed" on the ground (they will illuminate and your PFD will show (in white) "LNAV/VNAV" below TO/TO). If you've made any errors in programming, this is the time you will get messages on the FMC CDU (much better than messages in the air ;) ).Above 400', you can "engage" VNAV by pushing any of the CMD buttons. All autopilot modes require CMD for engagement.Perhaps I've misunderstood what you've said?Cheers.Q>

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Hi Q,I'll start again all over as I have mistakenly asked the wrong question re: VNAV. The problem is actually Auto Throttle not engaging during and after takeoff. Sorry to have confused everyone....:-roll Takeoff SetupFlight Directors On, Autothrottle On, LNAV armed, VNAV armed (20/1000,F5)TakeoffCtrl-Shift-G (Nothing Happens), so I use F4 (TO/GA) instead.During takeoff roll nothing annunciated on AT column, ie;blank. I was expecting HOLD (Is that right?)VrRotate, Gear up, engage L/C/R autopilot, LNAV capture, VNAV capture but the AT annunciation still blank.1000ftAC pitches down to speed up and clean up, F20-F10-F5-F1-Fup progressively, speeding up to 250kts. This is all done by the autopilot using elevators. Once the AC levels out at say 4000ft (Altitude Window), the speed runs over the 250kts into the barber pole, set in FMC, as the is no AT control.What I have to do usually is: press F1 (cuts A/T and thrust to idle), then F3 (Increase Thrust), and then fiddle around with THR or SPD (A/T mode), only then will the A/T engage and all is sweet.I'm not sure if it's me or just some bug in the system...No probs with CMD (A/P). Just the A/T.ThanksNot so joyous schtik..;(

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When you're at about 1000, press the VNAV button again even though it's engaged. Report back with your results.(edited for clarity)

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If TOGA is enabled, you should see something in the FMA. F4 is for full thrust, not TOGA. Try clicking on the screw next to the A/T switch. If the A/T is on but nothing is in the A/T FMA, click on VNAV or any speed function you want to use and it should re-enable.Ryan GamurotLucky to live Hawai'ihttp://www.virtualpilots.org/signatures/vpa296.png

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Like the guys are saying, there's gotta be an annunciation in that far left FMA. For TO, the autothrottle was not engaged. Thrust was was not under any automatic control, so when the airplane leveled off, it just continued to accelerate. Zoom. Into the bricks. Happens all the time, but is it just we gamers? We're gonna see this same kind of system modeled in the MD11. In that airplane, there is No wAy (short of some very fancy button pushin') to engage the Autopilot without also engaging the Autothrottle. On the MD, there is a single big button labeled "Autoflight." When the AP is engaged, so is the AT with that single button press, This button does not say "Autopilot / Autothrottle." This button is about Autoflight, and that's what it says. The autopilot and the autothrottle are critically cooperative . . . as we see repeatedly in this and LVLD's forum. So, is this something just we sim-pilots mess up? Consider what the MD designers considered. What you experienced (and demonstrated could occur) in this little ol' PMDG simulator is eXactly the thing the real world MD designers were aware could occur with a even (and even especially!) a professional crew . . . so don't feel too bad!Once we get the MD sim, there are other critical details the MD did right . . . and they did it right-er 10 years earli-er. Looking forward to that airplane. It'll be interesting to talk about the differences.

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"F4 is for full thrust, not TOGA. Try clicking on the screw next to the A/T switch."Ryan is probably on the money, here....F4 is manually advancing the throttles, not engaging the throttles in TO autothrottle mode.Sorry you had to go to all the bother of posting the pics (but at least you know how to post them now, now : )))) ).Cheers.Q>

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Many times I took off and after engaging CMD, I had to press VNAV a second time before "THRUST REF" would appear. Now I auto do it.This can be true using the screw OR simply using full throttle with the yoke. Sometimes AT works with 1 press of VNAV, other times not.I usually set my speed to 250kt's, gear up at 400', engage CMD and press VNAV until "THRUST REF" is displayed then use flap retraction schedule on speed tape. If I press CMD too soon I get an AP disconnect, so I wait a few seconds after gear up. If you time stuff right you never get an over speed message and stay at or below the 250kt speed restriction below 10,000'. At some point before or during flap retraction I press LNAV. When I reach MCP altitude the "TRUST REF" changes to "SPD" and the engine EICAS changes from CLB to CRZ.Works as advertised. Buck

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Ahhh Yes.. THE 'SCREW" !!! Tried everything but the "screw".. ;)All's well now. Thanks very much guys (and gals) for your assistance.muchas gracias!!:7 :-wave :-jumpy

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Dear Joystick (are you USB or Gameport enabled :) ?)Have a look at this for future reference :ops.precisionmanuals.com/wiki/PMDG_747-400_Type_Rating_Course_Autothrottle_Care_and_FeedingAs the guys above said PRESS TOGA through the screw. This will engage the AT in take off thrust mode. For 99.9% of operators it is unthinkable to take off in other way. All systems on this aircraft are custom. Hence, default FS9 automation functionality is irrelevant. Through the PMDG Options menu you can also assign Ctrl-Shift-G to TO/GA. If you have a registered version of FSUIPC you can then assign a button of your Joystick/Yoke to this function (select button for key press is the proper FSUIPC submenu).Best,Vangelis===================================== E. M. Vaos Precision Manuals Development Group www.precisionmanuals.com=====================================

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Thanks for more tips, will look up FSUIPC.Did try the Ctrl-Shift-G for TOGA but didnt work..anyway..Cheers:-beerchug

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