FMS/Autopilot - I'm doing something wrong

[chroode]

Hi, I've checked every post I could find and even watched the video "Putting it all together" and I can't figure out what I am doing wrong. 

I have a flight plan manually entered. I sent and set my Vspeeds. I have the FMS selected. I have the ATS in N1 TO.

When I get on the runway I push the NAV button, then the ATS button. The engines accelerate and the plane takes off.

I push the Autopilot, and nothing happens. The plane keeps going straight and it won't follow the FMS indicated direction. 

The ATS switches from N1 TO to SPEED.

 

What did I forget? Any suggestions?

Thanks

Chris

[bumbak]

i think first use HDG mode to intercept Lnav track:)

[Patman]

Be sure to press the Stab Trim switches during the checklist

[Graeme_77]

The NAV mode is not built to compute random intercepts - if the takeoff flight path (or any other flight path for that matter) does not intercept the nav track when you press NAV it will arm NAV rather than capture. You can see this with LNV1 in white on the FMAs.

FMAs are key to understanding any complex aircraft - even a 737 - the lights on the AP panel are there specifically to trick you! 

In this case you would need to use heading to steer onto an intercept track, arm NAV as you have done, and it will take over and guide the aircraft when intercepting the track. Something to check for when the flight plan doesn't begin at the end of the runway.

Don't look at the lights - look at the FMAs. And when you press any AP button read the new FMAs aloud - "TAKEOFF, ALT-S CAP, LNV1 WHITE" would have immediately identified the issue.

[Muchimi]

As far as I know, you don't engage autopilot on the runway, it's a bad idea usually for a number of reasons - I'll attempt to explain why.

What I do (and I may not have that completely right and there are variations on the theme here) is before you enter the runway set the heading bug to the runway heading (should be aligned with the runway) and arm the heading pressing HDG.  Verify your speed bug is set to VREF+20 (can be different with airline procedures), alt armed to the desired initial climb set by ATC as part of your clearance, or your charts if not in controlled space.   You have to follow the departure chart because it keeps you safe and out of the way of other traffic. 

Double check the MFD for any configuration warnings (should say TO configuration ok - if not - such as spoilers, yaw damper, etc... it will tell you what's missing) - double check your flaps.  Press the TOGA button on the throttle the PFD should say "TO/TO" in green.   Usually you do all that before you enter the runway so you're ready to go.   In the US you confirm you have received your takeoff clearance by turning your strobes on which tells the tower (and also tells other aircraft in the vicinity) visually you are starting your takeoff roll.

Then with toe brakes on you advance the throttles to 50% to verify engines stabilized so you don't have to slam on the brakes if something goes sideways, then release brakes and advance to take off max or press the ATS button that should read N1 TO.  The flight crew operation manual says ATS should engage automatically at 75% or so but I've not seen that in the 650 so I just press it.

Rotate at VR and once positive climb verified, retract the gear, by that time tower will give you a heading to follow after your initial turn instructions and you can engage autopilot 1,000 feet above the runway (or more) one the plane is stable in climb.  Because you are in HDG mode you will follow runway heading and can quickly turn to any heading specified by ATC.

Usually ATC will give you a turn instruction on take-off (left or right), and/or a specific heading to follow immediately after tower hands you over to the departure controller so LNAV is usually not the first mode you're in as you will be vectored by the departure controller until you are allowed to resume your own navigation.   Thus HDG mode is what you want.   For vertical you probably want VS mode too as FLC mode is typically too agressive for your passengers and you want comfortable transitions and small g forces, not fighter jet behaviors.  I also found in controlled space your chart says one thing, but ATC may tell you something different so FMS legs initially aren't followed that closely.

 

Remember that you are not alone in the sky - which is hard in x-plane I know without a traffic add-on and ATC.

If you ever fly online on VATSIM or pilot's edge - you'll quickly get what works and what doesn't.

 

 

[IronCroptop]

@MuchimiThank you for posting that very detailed description. I found it incredibly informative.