julesmusician
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Advantage Of TO/GA Switch On Autopilot

Sat Oct 29, 2005 2:44 am

Can a pilot answer what the advantage is of the TO/GA switch on both take off and go around? What does it do that a pilot can't do by just advancing the throttles and taking the aircraft into a climb? Is there some hidden benefit of its use?

Jules
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SlamClick
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RE: Advantage Of TO/GA Switch On Autopilot

Sat Oct 29, 2005 3:04 am

On the Airbus:

When the thrust levers are moved to the TOGA detent and flaps are at least position 1 and the aircraft is airborne or has been on the ground less than thirty seconds: It combines the SRS (Speed Reference System) vertical mode and the GA TRK (Go-Around Track) lateral mode of navigation for the command bars and/or autopilot.

That saves you a lot of button-pushing and knob twiddling at a time when you are apt to be rather busy. Not all missed approaches are just climb straight ahead. Some of them involve turns and intercepts and holds etc.

It also enables the thrust management system to operate the engine at any required power setting from just above an idle all the way up to Takeoff/Go-Around thrust.

For Boeing products it will do similar things but I've been away from them for a while.
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D5DBY
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RE: Advantage Of TO/GA Switch On Autopilot

Sat Oct 29, 2005 3:07 am

ive been thinking about this to..but cant you make a take-off with the AP if your AC if equipped with a TOGA function? and if you can...that I guess is nice for flight crew, to let the AP do the take-off....but im not sure the AP with TOGA function can do this....just speculation
 
julesmusician
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RE: Advantage Of TO/GA Switch On Autopilot

Sat Oct 29, 2005 5:31 am

But I thought everything was so simple these days?!

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Jetlagged
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RE: Advantage Of TO/GA Switch On Autopilot

Sat Oct 29, 2005 5:49 am

Most modern autopilots could probably handle a takeoff, but they aren't certified for it and it can't be selected.

The importance of the TOGA buttons is to switch the autopilot/autothrottle system from approach mode to go-around mode. Yes, the pilot could manually reselect the AP pitch mode and adjust the throttles manually or change the AT mode. However if you have a go-around call just before touchdown there's not a lot of time to do all that. The TOGA button, in one selection, takes care of it all. While this is happening the crew still have to retract flaps and gear, call ATC, etc. so it's a busy time.

Even with AP disengaged TOGA will put the flight director into go-around mode to command the appropriate pitch up for the selected flap angle.

During takeoff, TOGA selects the AT to takeoff power (the flight director will already be in takeoff mode by default). It's a convenient means of selecting this mode. Back in the day, they were merely GA buttons, then FFRATS came along so a selection was needed to put the throttles in takeoff mode, and the GA button became the TOGA button.
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julesmusician
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RE: Advantage Of TO/GA Switch On Autopilot

Sat Oct 29, 2005 8:05 am

thanks for all the information , so is the TOGA switch used during take off a lot or is it really a Go Around function mainly?
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Mr.BA
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RE: Advantage Of TO/GA Switch On Autopilot

Sat Oct 29, 2005 10:07 am

In Boeings the thrust levers are advanced manually from idle and when the engines are stabilised at about 40% N1 the TOGA switch is usually selected and thrust levers would advance automatically to the selected takeoff N1/EPR.

But this procedure should vary from airline to airline.  

Cheers  Smile

[Edited 2005-10-29 03:32:02]
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julesmusician
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RE: Advantage Of TO/GA Switch On Autopilot

Sat Nov 19, 2005 3:33 am

Still got a few questons about this:

Quoting Mr.BA (Reply 6):
thrust levers would advance automatically to the selected takeoff N1/EPR.

1) How does it know what you want the N1/EPR to be on take off? How do you select it?

2) Will the TOGA switch automatically pitch you up when you reach take off speed or do you still have to manually pull back the stick to get the aircraft off the ground?

Thanks, J
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Mr.BA
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RE: Advantage Of TO/GA Switch On Autopilot

Sat Nov 19, 2005 1:17 pm

Quoting Julesmusician (Reply 7):
How does it know what you want the N1/EPR to be on take off? How do you select it?

There is no fix N1/EPR for takeoff. The N1/EPR is determined by many factors, mainly runway length, weight, 2nd climb segment restrictions, flaps, runway conditions, OAT.. etc. After all these are taken into account, a certain N1/EPR would be determined by the pilot and the FMC for that particular takeoff and pushing of the TOGA switch would advance the throttles to this setting.

Quoting Julesmusician (Reply 7):
Will the TOGA switch automatically pitch you up when you reach take off speed or do you still have to manually pull back the stick to get the aircraft off the ground?

No. The TOGA switch is for throttle control purposes, it doesn't have anything in relation to any control columns.

Hope this helps  Smile
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RE: Advantage Of TO/GA Switch On Autopilot

Sat Nov 19, 2005 1:51 pm

As I understand it, TOGA will apply and maintain 'maximum' power (that is, the required N1 level subject to not overstressing the engines etc.). It can also be relied on to advance all the throttles evenly.

Jet engines take some seconds to spool up and down. Doing the same job manually would presumably require the pilot (or more likely the second pilot) fiddling with the throttles and watching N1 until the aircraft was about halfway down the runway before he/she could be sure that all the settings on all the engines were right.
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RE: Advantage Of TO/GA Switch On Autopilot

Sat Nov 19, 2005 10:15 pm

When every second matters in a Go around,Its better to have one switch do your job,rather than multiple functions that'll cost those valuable seconds.
regds
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julesmusician
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RE: Advantage Of TO/GA Switch On Autopilot

Sun Nov 20, 2005 2:05 am

OK so there must be something wrong with Flight Sim then as when you hit the TOGA switch just before touchdown it places the aircraft into a pitch up attitude and advances the throttle fully forward, or maybe that is just for the go around part of it?
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AAR90
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RE: Advantage Of TO/GA Switch On Autopilot

Sun Nov 20, 2005 5:22 am

Quoting Julesmusician (Reply 11):
OK so there must be something wrong with Flight Sim then as when you hit the TOGA switch just before touchdown it places the aircraft into a pitch up attitude and advances the throttle fully forward, or maybe that is just for the go around part of it?

"Hit" the TOGA switch "just before touchdown" = Go-Around mode activated.  spin 
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julesmusician
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RE: Advantage Of TO/GA Switch On Autopilot

Sun Nov 20, 2005 5:25 am

Perhaps hit wasn't the right word - touch gently in a totally calm state - are right the GO mode is different from the TO mode...I think I am beginning to understand  Wink
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RE: Advantage Of TO/GA Switch On Autopilot

Sun Nov 20, 2005 12:02 pm

Quoting Julesmusician (Reply 13):
right the GO mode is different from the TO mode...I think I am beginning to understand

First time I ever came across this feature it was named: "TO/GA"... meaning Take-Off and/or Go-Around switch. The "and" portion is the fact that the single switch has two functions. The "or" portion indicates you get either one or the other of the two functions, but never both at the same time. Even today I continue to use that particular spelling: "TO/GA." Keeps things simple for me.  old 
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RE: Advantage Of TO/GA Switch On Autopilot

Sun Nov 20, 2005 2:57 pm

Quoting Julesmusician (Reply 11):
OK so there must be something wrong with Flight Sim then as when you hit the TOGA switch just before touchdown it places the aircraft into a pitch up attitude and advances the throttle fully forward, or maybe that is just for the go around part of it?

As I pointed out in the other thread, the "stock" 737-400 (and 747-400) in MSFS doesn't behave like the real plane, and the controls are MUCH simplified. Try Dreamfleets 737-400 for a more realistic experience. I believe something like 90%+ of the controls are in place, and the autopilot, FMC and so on actually work pretty much like in the real plane. For more detailed and realistic sims, you might also want to try http://www.phoenix-simulation.co.uk/

Note, though, that this is still not a "real" sim. It's just much more real than the watered down version in plain vanilla MSFS.


But I would also think that pushing the throttles on an aircraft with underslung engines such as the 737 to the stops would produce at least some some pitch up moment.
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