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.

I would have disengaged the autopilot, opened the throttles and pulled to the shaker.

How times change.

I've flown planes without autothrottles

and with modern boeing autothrottles.

it was just so, so hard to move two big levers (or four for that matter) forward and back to control the engines.

go= forward

go for all you are worth, forward till you bend throttles over mechanical stops.

or

go...engage autothrottles to pre programmed thrust setting, watch and feel thrust levers move by themselves

but be sure clutching mechanism works properly and moves them together and make sure the thrust setting is correct


soon, there will be automatically tying shoe laces!

Thanks John. What you have said is pretty much similar to a procedure for the aircraft in type in the event of a windshear encounter(although there is an automatic windshear recovery system for the aircraft allowing the FD to command appropriate pitch and can be followed by the autopilot) but lets not get distracted by a microburst windshear here. Just a way to get more thrust which could be desired for other reasons as well.

Maybe I am getting caught up in words here, I'm just not sure what Maximum Available Thrust is with THR REF indicated. Max takeoff, max continuous, full climb thrust, CLB 1, CLB 2. Maybe I'll just try a second TO/GA push in the sim.

I think that is what happened to the Kalitta 747-200 in Colombia a few years back.

The possibility of doing damage to the engines is there. The alternative may be more dear.

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.



quoting initial "jazmmedstab" post and I'll be giving B 777 description.


If aircraft is detecting windshear with associated warnings ,you MUST press TOGA switches so as to activate windshear followup by flight director.

Thrust status will change from THR REF to THR .

As someone said THR REF is just the reference thrust commanded by FMS ( D-TO, CLB etc)

Per exemple in approach , as flaps are non 0 ang glide slope captured thrust reference changes to G/A ( indicated top left of EICAS) and you autothrottle in SPEED mode on your FMA .

If you then press TOGA switches to make a go around, you will have a FMA change to THR REF wich means your airplane in is go around mode , THR REF meaning in this case: engine thrust is just thrust to acheive 2000 ft/mn rate of climb (if just one click on TOGA switch) . If you press a second time on toga switches , you then have your reference thrust changed to full goaround engine thrust .


Regarding thrust situation awareness , my eyes scan goes from FMA of course ,to EICAS green thrust indication . This particuraly on engine failure until CON is selected

pause !


Refering to some post speaking of TOGA control law :

Whatever take off or goaround mode, indeed, when altitude rate is greater than 1200 ft/mn, elevator controls pitch to keep selected speed.

When altitude rate becommes negative, aircraft is controlledby pitch.

When rate is between 0 and 1200 ft/mn, there is a combination of speed control and pitch control. Kind of small difference if autopilot used 600 ft/mn replacing 1200 value to be simple !


Happy new year.

All “thrust references” are calculated values … where the result is dependent only on the parameters chosen … and they are always (at least more so than less so) based on efficiency and effectiveness of the “relationships” of those parameters at the anticipated normal ranges for the flight conditions expected.

…so, are we to believe that you would be perfectly confident in the airplane systems to the degree that you would allow the airplane to safely fly itself out of a windshear encounter? I think that doing so is very likely a result of either “over confidence” in the airplane systems or “under confidence” in the pilot flying … who do you know better … YOU … or the guy(s) who designed, developed, constructed, and installed that system … and how come he isn’t there with you when you have to make that decision?

Before you make any potentially life-altering decision on how to operate your AIRPLANE based on what you see, hear, and/or feel in a SIMULATOR, I would strongly suggest that you find out what kind of information was used to program that particular simulator for the specific conditions you desire to examine. The fact is that the simulator will do what it is programmed to do … and ONLY what it is programmed to do. Good input = good output … Bad input = bad output … and No input = potentially deadly output.

I think you meant to say “over speed” the engine. Unless they’ve made some remarkable advancements in jet engine technology that has escaped general notice, there is no such thing as a “thrust-limit” on a jet engine. As an example, I used to fly one that had a planned and used TO EPR of 2.83 – with water injection. There are limitations on "engine boost" that are applicable to internal combustion engines ... where additional pressure can be pumped into a cylinder to increase the power generated when ignition occurs ... and, in those cases, one can, indeed, "over-boost" an engine (pump too much air under pressure) into that pressure chamber - because of the structural integrity of that chamber. Additionally, as you probably know, 100% is not necessarily the real maximum rotation speed for any jet engine (you see maximum values all the time of 104%, 106%, and sometimes even higher); over-temp is a much more serious problem than over-speed; and if it is equipped with the necessary sensors and indicators, an increase in engine vibration above whatever is considered “normal” is also something that should be avoided. I’m relatively sure that if engine manufacturers could generate more “pressure” at the exhaust end of the engine in relationship to the “pressure” at the intake of that engine – without having to resort to dumping raw fuel into the burner sections (i.e., “after-burner”) - they would probably jump for joy. I’m not saying that one doesn’t need to know or respect engine limitations, but when it comes to IF or how hard I may have to hit the ground … I’m not at all worried about maintaining the integrity of that hunk of spinning metal.

And ... I, too, hope that each of you and each of your families' enjoy a peaceful, prosperous, and SAFE New Year!!

…there is an automatic windshear recovery system for the aircraft allowing the FD to command appropriate pitch and can be followed by the autopilot
No, you are to believe that Boeing says that this is a procedure which I repeated. Nothing more and nothing less. I don't think it is reasonable to expect the designer to accompany every flight that has windshear potential so no point bringing the subject up as it is not the basis for whether or not to be aware of manufacturers procedures and recommendations.


Maybe I'll just try a second TO/GA push in the sim.
It is quite possible that the sim could be different than the aircraft but I still think that useful information could be gained. Which of course is why we use the simulator. If a certain procedure does apply to the simulator, I should think that there is a high probability that it will apply in the aircraft as well. But as you suggest, no guarantees.

As earlier stated, the procedure is to manually advance thrust levers so this is more of a learning a bit more exercise.

There are different degrees of wind sheer. The AFDS perfectly capable of flying out of a moderate wind sheer. Why on earth would anyone in that case:

...infact why would you EVER do that for a wind sheer. What you are describing is terrain avoidance maneuver. Totally unnecessary for a wind sheer where ground contact is not a factor.

Thank god times have changed.

Relax, cosmo, these guys are just theorizing. Because they are theorists.

Cosmo, I am afraid this time you are not correct.
If 15 degrees NU still results in a negative VS, all you can do to avoid ground contact, is to pull up more. Up to the stick-shaker, if necessary.

This is common on all aircraft, I believe, after the DC10 accident in DFW.

I think you read what I wrote too fast... But I will elaborate:

Wind sheer escape maneuver does NOT call for raising pitch to stick shaker, but as you wrote 15 deg ANU. Even if this results in negative V/S, you hold 15 deg (or what ever value applicable to you aircraft), as long as ground contact is NOT a factor.

If ground contact becomes a factor, you are no longer flying a "wind sheer escape maneuver", and the wind sheer is no longer the priority. Because it's obviously far worse to risk a crash. Hence, the wind sheer escape transitions over to "terrain avoidance maneuver", which calls for raising the nose to intermittent stick shaker.

However, in e.g. 1500 feet during approach or takeoff, and getting into wind sheer, it makes no sense what so ever to raise the nose to stick shaker and risk going into a stall. In addition to not making sense, it is not correct procedure either.

737 Windshear Escape Maneuver
Manual flight:
• Disconnect autopilot.
• Press either TO/GA switch.
• Aggressively apply maximum*
thrust.
• Disconnect autothrottle.
• Simultaneously roll wings level and
rotate toward an initial pitch attitude of 15 °.
• Retract speedbrakes.
• Follow flight director TO/GA
guidance (if available).

Automatic flight:
• Press either TO/GA switch**.
• Verify TO/GA mode annunciation.
• Verify thrust advances to GA
power.
• Retract speedbrakes.
• Monitor system performance***.


GPWS Warning
• Disconnect autopilot.
• Disconnect autothrottle.
• Aggressively apply maximum* thrust.
• Simultaneously roll wings level and rotate to an initial pitch attitude of 20°.
• Retract speedbrakes.
• If terrain remains a threat, continue rotation up to the pitch limit indicator (if available) or stick shaker or initial buffet.

Cosmo, I see your point clearly. And it would indeed result in the same.
However, In my QRH, Maneuvers 11.1, pulling up to the stick shaker, is part of the "wind-shear escape maneuver".

I would be interested to see that quoted in full. The above is quoted from Boeing standard QRH, and is written as such in all the QRH I have from the previous companies where I worked.

Intermittent stick shaker is mentioned in the notes, as the upper pitch limit, i.e. it may necessary to lower the nose, below 15 degs ANU. Which of course makes sense if 15 degs would result in a stall.


...still the point is that there is no reason to "blindly" raise the nose to intermittent stick shaker for every wind sheer warning, as John Farley suggest.

Cosmo:

Trying to cut and paste, to no avail.

So, extract from QRH B737 rev.17, 17_07 dec12:

Man. 1.11

action, dot nr 5, "simultaneous roll the wings level and rotate towards an INITIAL pitch attitude of 15 degrees.

And then in the first note, the devil is always in the tail:

"Flight at intermediate stick shaker may be required to obtain a positive terrain clearance.. "

I do not think I have to refer to a different manoeuvre, while, in my opinion, this covers the exercise.

Of course, there is no reason to go to SS at the initial notation of windshear.

WHAT?
 

Just so I understand … you are saying (are you not) that Boeing has developed a procedure which pilots are perfectly welcome to use, and using this procedure will automatically recover the airplane from a windshear encounter, and, of course, you are aware that any procedure developed by Boeing, recommended by Boeing, and found in the Boeing operations manual, if used exactly as Boeing has recommended, will put Boeing directly in the sights of litigation should anything catastrophic occur … and Boeing is accepting this situation for windshear encounters. I just want to understand your comment.

Well, I shouldn’t be terribly surprised to see that irony is lost on some.

Once again … just to understand … you acknowledge that some things seen, felt, and/or heard in a simulator “could be different than the aircraft” but you are convinced that this “different from the aircraft” information is useful to you. Is that right? The point I was trying to make is that, indeed, sometimes there IS information contained in a simulator that is NOT like the airplane (which may result from its being improperly understood, improperly programmed, or completely absent in the simulator – meaning that the simulator WILL NOT act or respond like the airplane) – and I am telling you that I KNOW aircraft simulation, quite well, and I'm recommending that such differences be recognized and avoided at all costs – and if absolutely unavoidable, proper and complete instruction MUST be simultaneously accomplished to ensure that any incorrect information is NOT carried over into the operation of the airplane. In fact, I would suggest discussing such matters with someone exceptionally knowledgeable about and well versed in the operation of the airplane's systems and the impact of those systems on the airplane's performance, handling, and response ... and failing that, please discuss the legal implications involved when someone ignorantly does something in aviation … and I say this in the hope of ensuring the highest degree of safety possible.

I’m not sure how you can say that … no guarantees, but go ahead anyway? Please, re-read my response, above … and if that doesn’t do anything for you … I’d recommend reviewing the ABX DC-8 accident in Narrows, Va in December, 1996 … and if that doesn’t impress you, I’d recommend a vocation change.

I wouldn't sweat his vocation situation much, especially since he's obviously nowhere near aviation.

On a related note, I'm not altogether clear on what windshear escape procedures (in a simulator or otherwise) have to do with the crash you mentioned, but then I don't have three decades of writing FARs under my belt.

Refreshing to see an honest man 'round these parts, huh, OK465?