What prevents the autopilot from engaging?

[mkear 0]

Frequently when I fly the NGX,   the autopilot wont engage.    I suspect there is a setting I have missed somewhere but I can't find it.     Can anyone give me a hint as to what I might have missed?  

 

I have learned that the autopilot wont engage if: 

 

1. the IRS isnt properly aligned. 

2. the aircraft isnt in the air and above the minimum height AGL  (about 1500ft or so I think) 

3. the flight directors arent turned on. 

 

These are the only things i can find in the FCOM

 

Is there anything else?  

 

 

Cheers

Mike Kear

Windsor, NSW, Australia 

 

 

[Budbud 227]

Are you trimmed and controls at the center? The aircraft attitude must be stabilized before trying to engage the autopilot.

 

If you move the controls at the time you try to engage the autopilot it will be rejected without any warning.

 

"

The A/P cannot be engaged unless both of the following conditions are met :

- No force is applied to the control wheel or column.

- The Stabilizer Trim Autopilot Cutout Switch is at NORMAL.

"

 

And by the way the minimum autopilot engagement height is 400ft.

[mkear 0]

Thank you Budbud.  

 

I havent had this problem before,  I guess the new version of the NGX is a little more picky on this aspect than previously.    I'll have another look at that  - make sure the NGX is flying stabilised and in a stable climb when I try to engage the A/P

 

Cheers

MIke Kear

Windsor, NSW, Australia 

[Budbud 227]

There is also an option in the FMC called "Realistic AP engagement" which defines whether the AP can be engagement when the aircraft is out of the condition above. maybe the setting changed when you got to the new version?

[mkear 0]

THAT'S IT!!!!      Brilliant, Budbud.   That's where it changed.    I was looking about the settings, and changed that the other day!   It had been set to Realistic AP engagement = NO before.     That's why it's never bothered me before. 

 

Thanks!!!

 

Cheers

Mike Kear

Windsor, NSW, Australia. 

[Budbud 227]

Always glad to help!

Enjoy.

[ALF1 15]

All that said it would be nice to leave it there. One of the funnest things in the NGX is to hand fly and trim the airplane through most of the departure. Just follow the command bars and when everything is trimmed nicely engage A/P.

 

To have even more fun, lower the HUD and trim for the birdie in the cage. Your alignment will be perfect with the Flight Director if you accomplish that.

[Budbud 227]

I usually fly all the departures manually until established on climb at 250kt after the After takeoff checklist if it is a straight departure or until the last turn before the first long straight leg (which can be at more than 10000ft).

 

For more challenge, I only arm LNAV and VNAV on ground when I expect high workload with a lot of traffic and human ATC (I fly exclusively online). Otherwise, I takeoff with TOGA armed only and manage the transition to LNAV/VNAV, through HDG SEL (or LNAV if the terrain or the procedure commands so)  and LVL CH until clean config is reached.

 

It gets much more fun to fly than just engaging LNAV/VNAV and AP at 400ft!

[underdogdjr 0]

Thanks for these posts. I do have a problem though that seems to fall outside this advice and seems to happen each and every time I do a turnaround without ending the flight and reloading. If I land - go to gate - load up and take off I get this problem 100% of the time. Basically the AP won't engage after takeoff. The LNAV, VNAV, all other lights will light up but I can't engage either CMD button. Even with the FDs on, etc. It's just the CMD buttons won't light up and the AP won't engage. I have realistic AP off. I've tried loading cold and dark between flights to see if it resets the AP. I've tried just loading in the new route. No matter what I do on that second flight I can't engage the AP. I think I've tried every variation I can and can't figure this out. I've checked all the above requirements and made sure I don't have a failure or maintenance need. No luck. Anyone else have this or know how to fix it?

 

It makes it impossible to do a quick land, turnaround and take off. I have to either exit FSX or take off and load an old saved panel with a flight plan from a prior flight and then re-enter my new plan. Default states or Cold and Dark don't fix it.

 

 

[jmdriskell 178]

Thanks for the insite!

[Budbud 227]

Thanks for these posts. I do have a problem though that seems to fall outside this advice and seems to happen each and every time I do a turnaround without ending the flight and reloading. If I land - go to gate - load up and take off I get this problem 100% of the time. Basically the AP won't engage after takeoff. The LNAV, VNAV, all other lights will light up but I can't engage either CMD button. Even with the FDs on, etc. It's just the CMD buttons won't light up and the AP won't engage. I have realistic AP off. I've tried loading cold and dark between flights to see if it resets the AP. I've tried just loading in the new route. No matter what I do on that second flight I can't engage the AP. I think I've tried every variation I can and can't figure this out. I've checked all the above requirements and made sure I don't have a failure or maintenance need. No luck. Anyone else have this or know how to fix it?

 

It makes it impossible to do a quick land, turnaround and take off. I have to either exit FSX or take off and load an old saved panel with a flight plan from a prior flight and then re-enter my new plan. Default states or Cold and Dark don't fix it.

 

Do you any warning on the upper EICAS with regards to the A/P?

 

And silly question: Does the A/P disconnect bar in normal position?

 

I regularly do turnaround without leaving fsx and never have that problem.

Could you post a screenshot of the main panel with the MCP, PFD, ND and EICAS, and a screenshot of the overhead (including upper and lower parts)?

 

Also, even if I'm not sure it would do anything, you may delete all the panel states except for the one called default and recreate the ones you like just to rule out corrupted panel states.

 

If you have no warning, no failure and follows the procedures correctly, I hardly see what could be the cause of your issue.

[ALF1 15]

Make sure you

 

1) Disconnect the autopilot and autothrotle before landing

 

2) Switch to off both flight directors when you exit the runway

 

3) Have a valid route loaded activated and executed in the FMC

 

4) Turn on both flight directors in your preflight

 

You forgot to tell us the most important aspect of your problem. Do you have any flight director indications ? The autopilot is the muscle that makes the movements of the brain (Flight director).

 

No flight director, no autopilot.