737-800 TOGA query

[PelicanSquawk]

Hi I'm just trying to get my head around TOGA/thrust settings for take off and go around. I'll write what I understand for each scenario, and would appreciate being corrected or filled in on what I am missing:

Take-off with de-rate and assumed temp method:

1 press toga: Sets calculated assumed temp and de-rate thrust
second press of toga below 800ft: removes the assumed temperature reduced thrust and gives max for that particular de-rate setting
Second press if above 800ft: removes assumed temperature reduction and de-rate and gives maximum thrust?
Fire wall manually the thrust leavers: Removes de-rate and assumed temp reduction?

On approach:
1 press toga: Reduced G/A thrust 1000-2000fpm climb around 90%
second toga: Max G/A thrust =100% N1
Fire wall manually the thrust leavers: ? as above, or more?

Another aside query on the windshear scape manoeuvre it states in manual flight to aggressively apply full thrust, but with automation to only press TOGA once and verify, would this not mean different thrust settings for each?

Thanks in advance for your help.

PS

[FlyingStone]

Second push of TOGA below 800ft will just change the thrust limit to full GA thrust, but not the thrust itself. Above 800ft, the same thing happens, but the thrust levers advanced to full GA thrust as well. Note that full GA thrust is not always 100% N1, but it defends on altitude/OAT, and there is a table for it in the FCOM PI chapter.

Manually firewalling the thrust levers at any time provides maximum rated thrust, which is slightly higher than the TO/GA limit, and can be used at any time without damaging the engines, provided the EECs are in normal mode.

You are correct about the windshear manuever, but the automatic go-around on the 737 is only available with a dual channel approach, which is typically only flown during Cat 2/3 operatons, and even then only once FLARE is displayed as armed on the FMA (typically from around 1000ft AGL down). Anywhere outside of these conditions, pressing TOGA will disconnect the autopilot and you should follow the standard windshear escape manuever for manual flight. Typically, autolands aren't recommended in windshear conditions, and windshear conditions are quite rare when low visibility prevails.

[PelicanSquawk]

Thanks for this. Makes sense. Just one question, am I right in assuming "Max rated" is always 26k, and assumed temp removed? Even if 22k was selected prior to take off? And I guess as you mentioned before max rated is always higher than max TOGA? And TO/GA thrust is independent of any derate or assumed temperature selected as it is only a product of OAT and altitude?

And everything you wrote about the Wind shear escape manoeuvre for Cat 2/3 makes sense, thanks again.

[FlyingStone]

Full rated takeoff thrust (26K in your example) is achieved with thrust levers less than firewall. It is calculated purely as a product of altitude and OAT, irrespective of any derate and assumed temperature you might have set - think of it, it's the same as you get during a go-around (2nd push of TOGA), where there is no derate/assumed temperature set.

Maximum rated thrust is achieved with firewalled thrust levers. Engines can safely produce a bit more thrust than for normal takeoff/go-around operation, but that is only used during windshear and terrain escape manuevers.

Look at FCOM Vol. 2, under "EEC Normal Mode" for a better explanation.

[PelicanSquawk]

Thank you. I’ll reread the chapter also.

appreciate it.