Autopilot won't control VS??

[Guest]

I am new to the PIC, so please go easy on me if I am missing someting really stupid here. I am finding that often, after a take off, the AP won't take control of the climb from me.Take a look at the picture attached. You will see that speed is falling fast and I am in a steep climb, even though I have selected AP (above 1000ft) and VS is set at 2500fpm. I am still in total control of the climb, as you can see the AP is doing nothing, even though it looks like it is selected?I know I am missing something stupid here, so please somebody, tell me what am I doing wrong?Graham

[Guest]

Hmm...I don't know why this is happening, but let me try to solve your problem by asking a procedure question. Why are you using V/S in your climbout? VNAV would work best...Jon (KSEA)

[Guest]

I am still getting to grips with all the FMS settings needed to get VNAV to work corerctly, in the meantime I want to use VS.ThanksGraham

[Guest]

Hi Graham,The problem is probably that you are pulling on the stick !The autopilot tries to counter-act, but the elevator deflection is too important. Keep in mind that the stick is alive while the autopilot is engaged, so try again with the stick in neutral position. Regards,Laurent Crenier_____________________________767PIC Panel co-designer

[Guest]

If you don't want to use the FMC to help you withthe climb, then use FLCH and select the speed after you engage FLCH.Your picture shows you with a 30 degree nose up...that's not good ;-)A trip thorugh the FMC manual will save you a lot of frustration.Rob.

[Guest Stephan Haas]

After rotation I usually keep a 18 degr. nose up to hold V2+15. During climb out the nose lowers to app. 10 degr. (If I remeber well).So this 30 degr. is a bit over the top (to say the least)Kind regards,Stephan Haas

[Guest ilh]

I'm guessing the elevator trim was way out of the green on takeoff (nose up) and it is taking the autopilot a long time to bring it back. Did you check the elevator trim before takeoff?Lee Hetherington (KBOS)

[Guest MB327]

Right on Laurent!If you look at the status screen you can see that the elevator is pulled way back. KEEP IT NEUTRAL as Laurent says...

[Guest]

Thanks for the replies guys.The elevator trim was set to 4 and checked before I rolled down the runway.As for the pitch up, yes i agree it is very high, but it only went up while I was paying around trying to take the pic when I hit CMD it was in a nice 2000fpm but it did nothing. I kinda lost control while I rushed to take the pic. When it does work it usually takes over and correct any step climbs anyway, but when the pic was took it did nothing and no, I had no hands on the yoke pulling it back, honest! This has happened in a nice climb rate of 2-2500, it just doesn't take over the climb sometimes no matter what my attitude, trust me.I guess I will have to go back and try FLCH.Thanks for the advice, guess practice makes perfect and I have a long way to go :-))Cheers guysGraham

[Guest Ian_Riddell]

Just wondering if you retracted your flaps too soon, Graham? With not enough lift, the aicraft may be trying to pitch higher and higher to achieve the required vertical speed(?).Cheers.Ian.

[Guest]

Thanks for the reply IanI know I have included a picture with my original post, but this is no the only time this has happened, it has happened to me many times, with endless flap configurations. I appreciate that the pilot has some yoke control over the AP even when engaged, but you can usually let go of the yoke when in a reasonable climb and AP will take over and alter to the VS set. I am finding even if you are flying manually say at 2000FMP, then put AP on and the VS set to 2500fpm, if you let go of the controls the aircraft has been known to climb past 2500 and keep going. Normally for me the AP would hold at 2500, but occasionally it just refuses to do anything.As I said in my original post I am not imagining this, the AP is just not taking over from me in any way, no matter what my rate of climb. Even if I fly manually at selected AP VS then let go, it does nothing to hold it there.This is only happening occasionally and I guess from the sugestions above their is no real explanation for my particular problem.Thanks anyway for all your answers, much appreciate the responseGraham

[Tabs]

One other thing: You're in the basic A/P modes that are engaged by pressing CMD right after takeoff - HDG HOLD, for holding the runway heading, and V/S which is supposed to maintain the current V/S you were at when you hit the CMD button. (I think) Most of the time you wanna use LNAV or HDG SEL along with FLCH or VNAV. If you arm VNAV on the ground prior to taking off, it'll autoengage at 400ft after you press CMD. What exactly was giving you problems with setting up the VNAV in the FMC?

[Guest]

I am working on using VNAV, just haven't for that far into the FMC manual yet, how big...Lol!Will try FLCH from now on and see what I get.Thanks for the repy Tabs.