Autopilot Behavior On Takeoff

[rfazio1951]

I think this is normal, but I can’t figure out why. I’ve done it a few times and it puzzles me. On an IFR departure I set everything up before takeoff. Set radios, alt bug and course bug. Then I set the autopilot to heading and 800 ft per min up but the autopilot not engaged. This way on takeoff I can climb out and engage the autopilot when I want. But as soon as I start the takeoff roll the autopilot turns off, no heading an climb rate. No big deal, I just hit heading and turn it on but, why should it do that?

 

[airguy]

You are ENGAGING the autopilot prior to takeoff?

 

[rfazio1951]

No, I am arming it. ready to go so I can engage once safely in a climb.

But once I take off it is no longer armed it just goes away like it was off.

 

[skyview_user]

No, I am arming it. ready to go so I can engage once safely in a climb.

But once I take off it is no longer armed it just goes away like it was off.

IIRC this annoying "feature" was introduced with Rel. 14 or 15. It contradicts my philosophy "what can be done on ground should be done on ground".

 

[DHeal]

I too have tried to do what Richard suggests -- set up the desired AP flight parameters prior to departure and then activate these AP parameters after lift-off. Sure would be convenient if my SV could be advance programmed in this way.

 

[DBRV10]

Just a word of caution, you should not (read as SHALL NOT) climb in VS mode. You should use IAS for climbs.

My Instrument departure is set the heading bug, fly off the runway, as I accelerate through 120-125 knots, hit the IAS button (this captures it) and then if I want HDG/TRK or NAV I hit them.

Once they are armed and I confirm the FD is doing what it should, fly the FD and or engage the AP. Although I will usually hand fly the climb just to keep my hand in.

Hope that helps.