Go around thrust logic?

[jgoggi 65]

Can someone please explain how the go around thrust works? During landing if I press the TOGA switch it seems that the thrust does not increase or increases just a little in order to keep the airplane maintaining Vref, without a tendency to climb if the A/P is engaged. Further, I read on the FCTM that if I press TOGA  a second time, the thrust should increase to the maximum G/A thrust, but nothing happens if I press TOGA  a second time on the PMDG 777.

Thanks.

[downscc 1,327]

Maybe you are not in approach mode or FCS is not in descent mode, or if you are below 100 ft RA A/T will not respond. See FCOM 11.31.31 and 9.20.12; the PMDG simulation TOGA works pretty much exactly as outlined in the Boeing manuals.

[tcas_climb 45]

 

 

or if you are below 100 ft RA A/T will not respond

 

Hi, do you mean 2ft RA?

[downscc 1,327]

According to FCOM 9.20.12:  "or below 100 feet radio altitude on approach the autothrottle will not automatically activate."  Understand that this refers to the case where A/T is not already activated.

[tcas_climb 45]

ah i see

[jgoggi 65]

Well, I don't see an answer to my question in those FCOM pages. My doubt is about pitch and thrust and my precise question is: what does the A/T (and the AFCS) do when I press TOGA with A/P on? Do they command for example 15 degress nose up? Further, why doesn't the thrust go to the G/A thrust if I press the button twice?

[Michael Moe 494]

I would also like to add if it makes any differents on different GA legs in the FMC?

 

What if there is only an vector heading track out with no altitude/speed restraints ?

 

Or a legs based GA in the FMC with restraints .

 

 

 

Michael Moe

[Budbud 227]

Hi,

 

Well, I don't see an answer to my question in those FCOM pages. My doubt is about pitch and thrust and my precise question is: what does the A/T (and the AFCS) do when I press TOGA with A/P on? Do they command for example 15 degress nose up? Further, why doesn't the thrust go to the G/A thrust if I press the button twice?

 

 

The answer you are looking for is in the volume 2 of the FCOM at page 4.20.16:

 

With the first push of either TO/GA switch:

- roll and pitch activate in TO/GA

- autothrottl activates in thrust (THR) to establish a 2000FPM climb

- the AFDS increases pitch to hold the selected speed as thrust increases

- if current airspeed remains above the target speed for 5 seconds, the target airspeed is reset to current airspeed (to a maximum of the IAS/MACH window speed plus 25 knots)

 

And also:

"TO/GA is armed when flaps are out of up or glideslope is captured."

 

Finaly, have you set a missed approached altitude higher than the altitude at which you press TO/GA? I have not tested yet but I'm not would happen if you press TO/GA wth an altitude set to zero for example?

It doesn't seem to be a condition to have the TO/GA armed but just to be on the safe side...

[jgoggi 65]

- autothrottl activates in thrust (THR) to establish a 2000FPM climb

- the AFDS increases pitch to hold the selected speed as thrust increases

 

Ok, then there is definitely something wrong with the 777: I am stabilized on a LAND 3 approach, perfectly on the LOC AND G/S, gear down, flaps 30, speedbrakes armed, speed Vref+5. go around altitude set to 3000 ft on the MCP.

I press TOGA at about 500 ft and what happens? The indications TO/GA appear on the FMA (pitch and roll modes) but nothing else! There is just a very small thrust change and the airplane continues descending with a rate of about 500 fpm. I don't touch anything, the A/P is still on and I don't have hardware throttle/yoke connected.

 

Could you try please and see if you have the same or you really get a 2000 fpm climb?

Thank you!

[Budbud 227]

Hi,

 

I already did numerous go-around in various conditions (AP on/off, with different failures, with different flaps config and at different stages of the approach) and it always worked perfectly for me.

 

Maybe should you submit a ticket on the support website?

[jgoggi 65]

I made a video (sorry if it is not good, this is the first time for me) in which it can be clearly seen that when I press TOGA nothing happens :-(. The problem is that the A/T should change into THR, but it remains in SPD mode!! Why? What setting should I look into? 

 

http://youtu.be/sagJjRbFlfk

[tcas_climb 45]

What do you have the joystick throttle override option set to in the pmdg simulation options?

[jgoggi 65]

What do you have the joystick throttle override option set to in the pmdg simulation options?

 

I have 'only in HOLD mode'.

[tcas_climb 45]

Have you tried deleting fsuipc.ini?

 

Edit: and are you using one of the panel states that comes with pmdg, not a custom one or "previous flight" one?

[jgoggi 65]

I have even tried removing the FSUIPC4.dll file, but nothing changes. I'd be grateful if you could check and confirm that, when you press the TOGA switch during the approach, the thrust mode on the FMA goes into THR and does not remain in SPD. That's the problem, I keep getting SPD and not THR.

Thank you.