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Paul12

TOGA question

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I read that when taking off, press the TOGA switch after N1 is about 40 %.However I ignore pressing the TOGA

and just advance the throttle fully and take off begins without problems.

 

What would happen in the real world if the TOGA button is not pressed and the throttle advanced to full ?

Same as above ?

 

HubertWerni

 

 

 

 


Herbert Werni

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Pressing the TOGA switch engages the autothrottle and sets the calculated takeoff thrust.

 

Naturally, just firewalling the levers manually will spool the engines up, the aircraft will accelerate and you will take off. However, you will get full rated thrust on both engines rather than any assumed temperature or derate -- which is bad news if you calculated your V speeds using a derate as you may find yourself unable to maintain directional control in the event of an engine failure. The engine manufacturer will also be sending your airline a big maintenance bill if you do full-thrust takeoffs all the time, and dependent on how your engines are controlled (EEC/FADEC etc) you may well be able to overboost/overtemp the engines by shoving the thrust levers to the forward stop, which naturally will result in an even bigger bill.

 

Basically, it's a rather ham-fisted way of handling the aircraft.


Simon Kelsey

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What if I set it manually to thrust bugs on engine displays?

It sounds like same thing as TOGA, although in this case I have no FD active.


Alexander Zar

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No problem with that.

 

TOGA has nothing to do with the FD (in the 747/767: I assume also for the NG) on takeoff -- if you have the FDs switched off, engaging TOGA will not turn them on, nor will it change the mode (on the ground). It is simply an autothrottle mode that advances the thrust levers to the command N1 bug. Like all automation, if you'd rather do it yourself there's nothing stopping you: you're the pilot.

 

(There may be some other 'hidden' functions: pressing the TOGA switches often also initiates an FMS position update to the threshold of the selected departure runway).

 

This is not the case in the event of a go around, where pressing the TOGA switches also reconfigures the AFDS to get you out of (e.g.) LOC | GS and give you GA pitch and GA track. For this reason, pressing the TOGA switches to initiate a GA is highly recommended: not doing so may result in LOC | GS and lots of thrust  :blink:. 


Simon Kelsey

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TOGA has nothing to do with the FD (in the 747/767: I assume also for the NG) on takeoff -- if you have the FDs switched off, engaging TOGA will not turn them on, nor will it change the mode (on the ground). It is simply an autothrottle mode that advances the thrust levers to the command N1 bug. Like all automation, if you'd rather do it yourself there's nothing stopping you: you're the pilot.

 

When I flew DC10s, the TOGA button armed the flight directors for takeoff to command V2 engine out or V2+10. We would hit TOGA before starting engines during the preflight. When taking off, you would call for autothrottle on and the throttles would advance without TOGA. We would also TOGA after resetting flaps and trim on touch n gos. It would arm go around mode and alt cap. We do the same in the Gulfstream 5/550. We TOGA in the chocks before engine start to arm the pitch and roll Flight Guidance modes.

 

As for the NG, this is from the manual.

 

Pitch Modes

•TO/GA – Takeoff Engaged for takeoff by turning both F/D switches ON and pushing either TO/GA switch. Both F/Ds must be ON to engage TO/GA prior to starting takeoff.

The AFDS commands pitch attitude in the following order:

•10 degrees nose down until 60 knots IAS

•15 degrees nose up after 60 knots IAS

•15 degrees nose up after lift–off until a sufficient climb rate is acquired.

Then, pitch is commanded to maintain MCP speed plus 20 knots.TO/GA can also be engaged for takeoff with F/D switches OFF if a TO/GA switch is pushed after 80 knots IAS below 2000 feet AGL and prior to 150 seconds after lift–off.

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Yes, I watched the videos on youtube with iFly 737 take-offs and it is the same thing: despite the FD switch being on, the FD needles appear (turn active) only when TOGA is pressed (or when the AP is engaged during climb out).

I personally didn't mind not having FD during manual thrust take-offs, because the pitch it indicates is underestimated, if you follow the FD you will overspeed past V2+10 and I see this all the time on youtube, even PRO pilots gain too much speed and then decelerate (don't know whether a programming error or what...)

No FD on take off and I pitch it as much as necessary to maintain V2+10 (or that little white triangle on ND display, and it doesn't take me more than +2000f/m on mid range flights with 25-35K lb fuel) until AP engagement.

I'm not a professional pilot and thus may sound unprofessional, for that reason I find compromises between the ways pros fly it and the convenience of the sim -) 


Alexander Zar

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TOGA has nothing to do with the FD (in the 747/767: I assume also for the NG) on takeoff -- if you have the FDs switched off, engaging TOGA will not turn them on, nor will it change the mode (on the ground). It is simply an autothrottle mode that advances the thrust levers to the command N1 bug. Like all automation, if you'd rather do it yourself there's nothing stopping you: you're the pilot.

 

Not quite. TOGA itself moves the FD bars just like any MCP mode change would.

 

Even in a 172 (though, in this case, it's just "GA" and not "TOGA"), it'll give you the pitch bar movement for the initial climb segment.


Kyle Rodgers

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personally didn't mind not having FD during manual thrust take-offs, because the pitch it indicates is underestimated, if you follow the FD you will overspeed past V2+10 and I see this all the time on youtube, even PRO pilots gain too much speed and then decelerate (don't know whether a programming error or what...)

Interesting, I've never had an issue with that in flight sim. Sounds like you are in need of a derate or faster rotation. The NG commands in stages and gets you to V2+20 normally. In the real world i've only seen it in the DC10 at very light weights, the FD would command to it's limit of 22 degrees while operationally we were limited to 25 degrees. In any case we went to the V bars and cleaned up if needed. In the GV/550, it's over powered and it accels very quickly after lift off. You have to increase your rate of rotation to get close to V2+10. The system in that jet will give you a variance from V2 on up based on the speed you have attained after lift off. It will then command that speed initially. The pitch is so high that we select vert speed to 2500fpm to keep the pitch near 15 degrees if there are no other climb requirements. I've seen 9000ft per minute light weight when chasing command bars.

 

You really don't need flight directors but they come in handy when:

 

* 6158 type check/refreshers - FD keeps you on point with very little deviations during airwork.

* Engine out departure - Picture will be different and the FD helps you resist the urge to pitch too high to    

  normal. HUD is awesome engine out.

* Low vis departure - Helps you fly a nice jet with no outside reference, the HUD is money.

* Strict/complex departures - If you have to be very precise, the FD works like a pro and makes things very

  easy if things are set correctly.

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Not quite. TOGA itself moves the FD bars just like any MCP mode change would.

 

Apologies -- this is almost certainly a hole in my NG-specific knowledge! (I'm fairly certain that on the Jumbo and 767 selecting the FDs ON on the ground puts them in to TOGA pitch/roll with the initial 15 degree up pitch command, and although I haven't done a manual-thrust takeoff (probably ever), given that the FD is active in TOGA | TOGA I don't see why the command bars wouldn't function as normal. Disclaimer: haven't checked this in the books (yet!)).

 

 

 


I personally didn't mind not having FD during manual thrust take-offs, because the pitch it indicates is underestimated, if you follow the FD you will overspeed past V2+10 and I see this all the time on youtube, even PRO pilots gain too much speed and then decelerate (don't know whether a programming error or what...)

 

As Rick says, I'd check your rotation technique. Also, I forget the precise wording, but I seem to recall that there's normally a note cautioning against using the FD for rotation guidance per se: you 'fly through' it (i.e. rotate at 3 deg/sec towards 15 degrees) until airborne and climbing away at which point you can then then transition to the FD guidance.


Simon Kelsey

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I'm fairly certain that on the Jumbo and 767 selecting the FDs ON on the ground puts them in to TOGA pitch/roll with the initial 15 degree up pitch command

True. The 737NG TOGA mode logic is a bit of a throwback. IIRC the 737 Classic was the first Boeing with a TOGA mode. Later Boeings have a more consistent approach, with takeoff guidance activated by switching on the FD, as you say.


ki9cAAb.jpg

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That's the mistake... V2+20. Perhaps the FD bar was commanding me to pitch the nose down to accelerate to that, and I've been climbing at V2+10. Gotta try it again...

Yes, the tutorial does say V2+20, I mix up things/airplanes and mess up.


Alexander Zar

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