Flight director off during approach (747)

[morph10 2]

Hi

Would love to know does the flight director get turned off during approach (before landing) in case of a go around? As I am aware that you cannot turn off the approach button on go around when flight directors are still engaged.

Edited February 1, 2019 by morph10

[scandinavian13 5,192]

53 minutes ago, morph10 said:

Would love to know does the flight director get turned off during approach (before landing) in case of a go around? As I am aware that you cannot turn off the approach button on go around when flight directors are still engaged.

Same way you turned it on at the beginning of the flight: the F/D switch on the extreme left or right of the MCP.

Make sure to have a look at and fly the tutorial.

[Ephedrin 418]

But normally it only is turned off during a visual approach when the reference is your eyes. During any instrument approaches you use the FD for guidance. For a go around you would press the TOGA buttons on the thrust levers (index or middle finger in the real airplane) 

you would recycle the FD (off-on) to exit the app mode during an RNAV approach when you decent below the initial approach fix altitude and the PNF resets the MCP to the go around altitude. This way the FD bars don‘t provide any decent path info anymore (I THINK they assist you with pitch guidance for the speed set on the MCP) but in case of a go around you immediately have g/a pitch guidance.

[morph10 2]

Thanks Ephedrin that makes more sense. 

The reason I ask was that yesterday I had to do a go around for the first time in the 747, the mistake I made was to manually apply thrust rather than pressing the TOGA button, as a result I could not disengage the APP mode until I turned off the FDs. 

So I take it that if I just press the TOGA button on go around this will automatically disengage the APP mode?

[sloppysmusic 239]

3 hours ago, morph10 said:

So I take it that if I just press the TOGA button on go around this will automatically disengage the APP mode

Yes pressing toga will deactivate APP mode and the approach will be deleted from the fmc while you make your way to the Map missed approach point. Then you add the approach again and try it once more. 

[Ephedrin 418]

5 hours ago, morph10 said:

Thanks Ephedrin that makes more sense. 

The reason I ask was that yesterday I had to do a go around for the first time in the 747, the mistake I made was to manually apply thrust rather than pressing the TOGA button, as a result I could not disengage the APP mode until I turned off the FDs. 

So I take it that if I just press the TOGA button on go around this will automatically disengage the APP mode?

It's important that you understand the "language" of the airplane. The MCP buttons light up when a mode can be disengaged or disarmed by pressing that buton again. You might have noticed that "APP" lights up when you ARM it, but extiguishes as soon as the approach mode is active. this means you can't turn it off anymore (safety reasons). You have to either go around (TOGA button) or disconnect both flight directors. 

Edited February 2, 2019 by Ephedrin

[morph10 2]

Thanks Sloppysmusic and Ephedrin for your help, it all makes sense now.

[vc10man 732]

8 minutes ago, morph10 said:

Thanks Sloppysmusic and Ephedrin for your help, it all makes sense now.

+++1 from me too.

[Ephedrin 418]

Welcome 🙂

[sloppysmusic 239]

Welcome guys! A point to read up on in the manual is that sometimes even if the FDs are both OFF the plane will turn them ON for a climb following a Go AROUND or TAKEOFF. Pressing that TOGA button triggers a whole number of interesting processes. Enjoy !

[Sekkha 15]

13 hours ago, Ephedrin said:

 You might have noticed that "APP" lights up when you ARM it, but extiguishes as soon as the approach mode is active

are you sure about that?   On the 744 ?   Not for me...

Edited February 3, 2019 by Sekkha

[Ephedrin 418]

Every Boeing 7x7 does that (except maybe the 717). As soon as the approach mode is active the light goes off. The lights do NOT mean, that a mode is active, it only means it can be switched off again. Armed or active is read from the FMA (above the artificial horizon). 

Edited February 3, 2019 by Ephedrin

[Sekkha 15]

 we must be talking about different things....  :)

 

[berts 97]

On 2/2/2019 at 9:10 PM, Ephedrin said:

It's important that you understand the "language" of the airplane. The MCP buttons light up when a mode can be disengaged or disarmed by pressing that buton again. You might have noticed that "APP" lights up when you ARM it, but extiguishes as soon as the approach mode is active. this means you can't turn it off anymore (safety reasons).

Sorry, but this is simply not how it works, because the white light in the 744's MCP APP switch will remain on whenever the Approach Mode is active.

The  "language" of the Autopilot/Flight Director system (AFDS) is always determined using the FMA annunciations in each pilot's PFD and not by the lights in the MCP's buttons.  Pushing the APP switch arms/selects the AFDS in LOC and G/S modes and the white APP switch light will stay illuminated until the APP mode is deactivated in one of these possible ways:-

1) By pushing the APP switch a second time before LOC and G/S capture.

2) By selecting TOGA after LOC and G/S capture.

3) By disengaging the A/P and turning off both FD's after LOC and G/S capture.

4) By selecting a pitch mode other than VNAV when the G/S is captured and the LOC is armed.

5) By selecting a roll mode other than LNAV when the LOC is captured and the G/S is armed.

6) By selecting LOC mode when the LOC is captured and the G/S is armed (this then becomes a localiser approach).

7) By selecting LNAV, VNAV or LOC before the localiser and glideslope are captured.

20 hours ago, sloppysmusic said:

Welcome guys! A point to read up on in the manual is that sometimes even if the FDs are both OFF the plane will turn them ON for a climb following a Go AROUND or TAKEOFF. Pressing that TOGA button triggers a whole number of interesting processes. Enjoy !

Yes, if the Flaps are not UP and the airspeed is >80kts and they get even more interesting when TOGA is pressed a second time!

 

[swood721 28]

The APP light bar on the MCP stays illuminated on the 757/767. Also, in order to get out of approach mode, not only do the flight directors need to be turned off but the autopilot must be off as well. I’ve never flown the 747 but I assume it’s similar to the 757/767.