TOGA mecanics on Takeoff

[Ram 0]

Hi, I don't know if it is a bug or something I don't understand about the airplane, but I am not able to replicate the intended behavior of the autopilot during take off. SID is setup, I have LNAV selected on the MCP and armed on the FMA, AT is also ARMED on the FMA. So I select 40% N1 with my throttle, then I press the TOGA hotspot below the course select knob. On the FMA I expect to see N1, HDG/SEL and TO/GA but there is only the N1, the roll and pitch mods are empty. See the screen shots below, first one of before I press toga, second one after I press TOGA. N1 on the FMA is now THR HLD as expected but no roll or pitch mode have been activated by the TOGA. What am I missing?

 

 

Thanks for any help,

Ram Homier

Edited September 11, 2017 by Ram
forgot to sign the post

[JoeDiamond 67]

You have to have both flight directors turned on.  In your screenshot the FO's flight director is off.

[Jim Erwin 7]

Roll mode can't be engaged until 400 feet. You are still on the ground. I don't see any pitch mode selected on MCP. 

Jim Erwin

[Ram 0]

10 hours ago, Jim Erwin said:

Roll mode can't be engaged until 400 feet. You are still on the ground. I don't see any pitch mode selected on MCP. 

Jim Erwin

I am then trying to understand why it does on his tutorial video 

 

But then there is no roll mode engaged in this other video from the same person. 

 

10 hours ago, JoeDiamond said:

You have to have both flight directors turned on.  In your screenshot the FO's flight director is off.

You are right, that fixed the issue. Thanks.

 

 

So to summarize I have now fixed the issue of not having both FD turned on and I see the same behavior as flightdeck2sim during his rejected T/O tutorial. I still don't understand the behavior we can see in his takeoff tutorial. Could it be depending on the way the FMC is programmed? Some kind of SID or something else?

[scandinavian13 5,192]

19 minutes ago, Ram said:

So to summarize I have now fixed the issue of not having both FD turned on and I see the same behavior as flightdeck2sim during his rejected T/O tutorial. I still don't understand the behavior we can see in his takeoff tutorial. Could it be depending on the way the FMC is programmed? Some kind of SID or something else?

I wouldn't get too distracted by it. It's all pretty situational. In this case, though, you can clearly see it was on HDG SEL (with LNAV armed) for the first roll, and simply LNAV armed on the second one. Had the roll progressed, and had he climbed out, LNAV would have become active after 400 AGL (I believe that's the altitude, off memory).

[JoeDiamond 67]

6 minutes ago, scandinavian13 said:

Had the roll progressed, and had he climbed out, LNAV would have become active after 400 AGL (I believe that's the altitude, off memory).

if LNAV is armed in the ground it should become active at 50 feet.

[Ram 0]

1 hour ago, scandinavian13 said:

I wouldn't get too distracted by it. It's all pretty situational. In this case, though, you can clearly see it was on HDG SEL (with LNAV armed) for the first roll, and simply LNAV armed on the second one. Had the roll progressed, and had he climbed out, LNAV would have become active after 400 AGL (I believe that's the altitude, off memory).

Maybe I am blind but I do not see HDG SEL on the MCP in the videos. He hits LNAV and it arms it as shown on the FMA. Than on selecting TOGA it arms the HDG select as seen on the FMA. That seemed strange and I just wanted to understand why and why not. But you are right it might be too situational.

[scandinavian13 5,192]

1 hour ago, JoeDiamond said:

if LNAV is armed in the ground it should become active at 50 feet.

Ah...is 400 VNAV? So many numbers...

7 minutes ago, Ram said:

Maybe I am blind but I do not see HDG SEL on the MCP in the videos. He hits LNAV and it arms it as shown on the FMA. Than on selecting TOGA it arms the HDG select as seen on the FMA. That seemed strange and I just wanted to understand why and why not. But you are right it might be too situational.

HDG SEL showed up on the FMA. I didn't look too closely at the MCP, as it only tells part of the story (you'll note that the lights will occasionally go out, even if that mode is still active). The livery he is using may have HDG SEL instead of wings level as the TOGA option.

[JoeDiamond 67]

55 minutes ago, scandinavian13 said:

Ah...is 400 VNAV? So many numbers...

Correct.  VNAV, if armed prior to takeoff will engage at 400' AGL.

If you arm LNAV on the ground prior to takeoff it will engage at 50' AGL.  If it was not armed on the ground then you can engage it manually after reaching 400' AGL.

[downscc 1,327]

44 minutes ago, JoeDiamond said:

If it was not armed on the ground then you can engage it manually after reaching 400' AGL.

This is probably related to the 400 AGL that most TERPS departures extend the centerline cone before providing obstacle clearance for heading changes.  I remember my IP demanding 400 AGL before banking even when severe clear and I still use that.