windshear/TOGA
 

I should now the asnwer to this already but I want to make sure. You are in a modern Boeing doing a derated thrust takeoff. After selecting TOGA, you see THR REF displayed on your FMA. Soon after liftoff you encounter a windshear and desire maximum available thrust to escape the windshear. To achieve this, you can press TOGA again and now you will have full rated takeoff thrust.

Also, with all systems working and configured nomally what happens during this windshear encounter if you instead push the thrust levers fully forward. Full rated TO thrust which will be the same as if you had pressed TOGA.

After take off you will not get take off thrust as the thrust mode will change to climb ( see take-off page transit to climb page on ams), assuming the ground/air system is working. The windshear escape manoeuvre and related pitch and power it gives can be found in the systems manual, the explanation of how much thrust is given is in the systems manual, although boeing state " max trust is available at the forward stop". the availability of the windshear system alerts and reactions of the system depends on altitude. You have many different questions rolled into one and the answer does not exist in one area alone. In a nutshell, if you advance the thrust levers to the forward stop full power for the phase of flight is available but if the windshear escape manoeuvre is triggered then initially FDs will command approx 600fpm until speed is recovered then the pitch will adjust.

After lift off and with speed greater than 80kts pressing TOGA disarms LNAV and VNAV and gets rid of any takeoff or assumed temperature reduction. If auto throttle is in HOLD it will activate in THR REF

[QUOTfE]After selecting TOGA, you see THR REF displayed on your FMA[/QUOTE]
Never seen THR REF on a modern 737 FMA.
You will see N1 then at 84 kts ThR HLD then at 800 ft ARM.

Once the AT is in ARM mode(above 800 ft),you will get n1 limit for 26K.(ie you derate 24 k from a 26k ).

AT must be disconnected.

If not and the AT is in ARM mode,you will get,by setting the thrust levers to the full forward position the full rate of your engine rating.(ie 27300 lbs for a 26k).
In that case you will overthrust the engine.(if you go more than the N 1 limit).

No.
If you press toga again at 800 ft you will get MaX thrust for the ouside temp and pressure altitude,if you fire wall the engines,you will get full rated thrust and will overthrust the engines.

Firewall the engines is only when MAX thrust is not sufficient and you are descending,then its better to overthrust the engines than hitting terra ferma.:ok:

There are several different 'modern' Boeings with different setups :) I see THR REF every time I fly :)

MANUAL FLIGHT • Disengage autopilot • Push either TO/GA switch • Aggressively apply maximum* thrust • Disconnect autothrottle(s) • Simultaneously roll wings level and rotate toward an initial pitch attitude of 15° • Retract speedbrakes • Follow flight director TO/GA guidance (if available)

Don't try and out think the system.

In the 744 and 748, THRUST REF will change to HOLD at about 65 KIAS on the takeoff roll. Pushing the TOGA switch AND pushing the thrust levers full forward will ensure TOGA is engaged for Autopilot and FD reference, as well as ensure full takeoff thrust.

I think this is the answer I am looking for. It is on the 747. At 65 knots we do get HOLD but it seems to go back to THR REF at 400 feet.

Therefore, if correct, pressing TOGA will give full rated thrust for the windshear escape maneuver, not derated or assumed temperature thrust. This will be the case whether the autothrottle is in HOLD or THR REF. Meanwhile if you were still on the ground and encounter windshear, pressing the TOGA button a second time does not increase thrust from its derate/ATM setting. Is this all correct.

Be aware, there is a Boeing Bulletin about arming VNAV on the ground with certain levels of software, in this event VNAV will remain engaged and a second push of TOGA switch is required to get correct FD guidance for the WS recovery.

I'm a 777 guy, so this may or may not help you.

On the ground, if A/T status is HOLD, you have to push up the thrust levers yourself. Pushing TOGA will not increase your thrust, it will only cancel LNAV & VNAV. On the ground, any time you see HOLD annunciated, the thrust levers belong to you.

Once airborne, pushing TOGA will cancel derates and below 400', give you TOGA roll and above 400', give you TOGA roll and pitch.

There's more to this that you'll find in your manuals. It's pretty important to know what happens if you push TOGA. For example, if you push TOGA after an engine failure don't expect it to follow LNAV (you most likely don't want it to of course) and more importantly, don't expect it to accelerate at your flap retraction altitude without further intervention from you if you've cancelled VNAV.

I can think of one place you do want LNAV after an engine failure....Hong Kong. Continue on the published departure procedure.

Thanks for the other information,

I am interested in what the F/D will command after a windshear warning when the TOGA switches are pushed (767).

I have found this quote elsewhere..

"If vertical speed is less than 600 ft/min (like in a performance degrading windshear) it commands constant 15 degrees pitch.
If VS is between 600 and 1200 ft/min it blends a constant pitch with speed through elevators logic, weighted by exact VS.
VS > 1200 ft/min (normal takeoff and climb) it command speed through elevators".

Can anyone shed any light on this as it is not in any manuals I have seen, and which a/c it applies to.

Different aircraft types, different modes.

JammedStab - Please refer to the type and model you're asking about!

For 737, you never get any sort of take-off thrust (either with or without derate) after pressing TOGA when airborne. It won't cancel anything out, it will completely change mode:

After airborne you get GO AROUND THRUST limit. Nothing more nothing less.

...and be very aware that if the throttles are still in hold (THR HLD, i.e. below 800 feet), you do NOT get any increase in thrust what so ever! Only the N1 limit bugs will move, but since the throttle is in hold, it will stay at the takeoff thrust selected (with derates/assumes etc.). Hence, you would then have to move the throttles yourself - either to the N1 limit bug, or firewall as needed - this is really something any 737 pilot must know.

Above 800 feet, the auto throttle changes to ARM. That mean the auto throttle is now able to move the thrust levers if so commanded. Pressing TOGA above 800 thereby changes thrust limit to GA (as indicated by the N1 limit bugs moving to that limit), and the thrust will automatically advance.

Here is what Boeing has to say about it:
(With second press they are referring to the initiation of the takeoff roll as the FIRST press).

Above 2000 and flaps retracted (which ever is later), NOTHING will happen if you press the TOGA switch.

That JammedStab is truly the Renaissance Man of aviation. Every week he's on a different airplane, in a different country, in a different type of operation.

I confess myself jealous.

747-400.

I know the procedure is of course to manually advance thrust which will be limited by the EEC's but I was just curious what second TO/GA push would do(on ground and when airborne). This question based on the difference in go-around thrust for one TO/GA push and two TO/GA pushes.

To 5LY,

Sure you did not get mixed up in your second paragraph?

There is no one/two push for takeoff. It's only for go around. Of course there is a first push too, and that is when you initiate takeoff with the toga push. There after there is only ONE push, which will give you go around thrust as described in my previous post. This is valid for 737, but I would wonder if it was much different on 744, due to commonality.

I am beginning to wonder how people can ask these sorts of questions, and allegedly at the same time operate the aircrafts in question!

Completely agree, Cosmo. But that is aviation today. Get used.

The manual says "If more thrust is needed (up to maximum thrust) when the airplane is on the ground and HOLD mode is displayed, the thrust levers must be manually advanced. After the airplane is in the air, pushing a TO/GA switch advances the thrust levers to maximum available thrust and THR REF is annunciated.".

For the airborne part, it doesn't say if there is a difference between being in HOLD mode(up to 400') or when you are back to THR REF. One might answer that you are already in THR REF mode above 400' but that could be CLB2 or CLB1 if they were selected. It does say "maximum available thrust" but just wanted confirmation that it was full climb thrust.

Sorry if you don't like me asking questions like this for clarification. Intelligent responses appreciated.