Toga Limit
 

Hello everybody,
scenario: t/o is performed at reduced thrust/flex thrust.If after V1 eng fail and continue t/o with out selecting full t/o pwr or TOGA are you still limited by 10 min time ? all inputs are appreciated thanks

Are you talking about the Airbus? The name of the knotch says it allready: ''Max continious thrust'', so any powersetting at or below ''Max cont thrust'' can be selected for an undefined ammount of time :ok:

Depends on the engine manufacturers limitations - RR may be 10 mins (eng.out) on full power, but P+W only 5 mins. For ease of operation, as far as I know, the limitations for take-off/Go-around are the same for full power and reduced/derated take-off power.

I am sure that you do not understand the labels on the detent and the meaning of thrust lever being placed in it. The procedure how to select MCT from takeoff power is to move the levers from the FLEX/MCT detent into the FLEX/MCT detent and you have a different powersetting.

Gearpins: I think yes, for all you know the actual tkof setting may be still above MCT so you need to observe the engine limitations. If your actual flex puts you below MCT then as you set it nothing happens, or even better (?) you get a thrust increase. But that is just my speculation as I do not know if any reduced thrust (regulatory max 25%) would be less than MCT and what would be the A/THR reaction to it. What would a pilot do manually is well clear, there are options.

Either way around, after 10 minutes you cannot go wrong.

FD,
(the un-real)

Thank you for knowing me from three lines of text:ugh:
And since to your expert opinion I am such a novice, can you please explain me how to move the thrustlevers from the FLEX/MCT detent to the FLEX/MCT detent? :rolleyes:

If you try to explain the procedure, do it correctly please:
If you make a take off with a low GW and with reduced power you may chose not to select TOGA with an engine failure. Only after reaching the engine out acceleration altitude you have to move the thrust levers shortly out of and into the FLEX/MCT detent again to remove the respective FMA and to set MCT thrust in stead of reduced takoff thrust. It will not take you 10 minutes to reach the engine out acceleration altitude. So like I said before if you have the thrust levers in the MCT detent or below you will not be limited to 10 minutes in the respective powersetting!

Like skiesfull allready said there are also engines limited to 5 minutes TOGA power. This is not only type limited but may also be different between two operators. The 10 minutes can be bought extra with airbus such as the 15 knots tailwind in stead of 10 knots (different story).
In our fleet we have two IAE aircraft from different operators and one has 5 minutes max TOGA and the other 10 minutes...

Ok let me clarify:TOGA limit may be 5 or 10 min agreed.
On t/offs at high gw, from high alt airfield (and obst) one would exceed the 10 min limit in trying to climb above the obst. hence the question:uhoh:

[The correct procedure is: after clean up and reaching green dot and not after reaching acceleration altitude move the thrust levers in the direction of climb and then back to flex/mct
Altough the same detent Flex and MCT are two different power settings, FLEX can be above or below MCT and thus the time limit does apply, altough this is purely theoretical keep the thrust you need as long as you need it and record the time in the trouble report.

That's why on your performance calculation during your preflight preparation you get a maximum engine out acceleration altitude and have an escape route wich you follow in case of N-1.

We chose the max engine out acc. alt or the MSA wichever is less. If your max engine out acceleration altitude is less than then MSA. You climb to the acceleration altitude. Push to level off, at S speed flaps 0, open climb to (at least) MSA and thrustlevers to MCT if selected TOGA.

@sarah737, oufcourse you have to apply the climb procedure as described, I just wanted to let the know when you move the thrustlevers. Thank you on correcting me that you have to move them to climb and then to flex again :ok:

I state my question once again: if I choose not to select toga do I still have to observe time limit on my flex thrust???:ugh:

What is the alternative?

Will you hit the obstacle if you reduce thrust? That might not be a good idea.

Will you clear the obstacle if you do not reduce thrust? Burning out an engine in that case may not be a good idea...

Consider

(a) in the early days of reduced thrust ops, Qantas, one of the early proponents, had the eyebrow raising situation where a crew noted that climb thrust reduction involved pushing the throttles up to set climb power. Evidently the captain thought this a little odd. Shortly after it was related back to Wal Stack (the ops engineer boss at the time and a thoroughly lovely chap), they put a restriction in the system to limit the maximum extent of flex permitted. This was a long time ago .. probably in the 60s ? .. Wal related the tale during a lecture at which I was present.

(b) whether flex thrust is below MCT or not, the TO limit ordinarily should be observed for procedural standardisation.

(c) with newer and fancier engine controls, there may be considerations relating to the consequences of particular detent locations or computer selections.


Also, folks, there are no sheep stations at stake .. please try to keep the tone of things on a professional level rather than getting excited to the point of being aggressive ..

I don't think I've ever read a more convoluted bunch of 'answers' to a simple question in my life. Mate, the simple book answer is yes. You must apply the limit in the scenario you described. Of course, life isn't simple and you may CHOOSE to exceed that limit in order to achieve obstacle clearance but you will have an exceedence. Hope that helps. Cheers.

ah finally!!!!!
john_tullamarine &TineeTim thank you.the reason for my question is: (this could be silly but..) A situation where,due to high alt and obst limit wt I am forced to use TOGA. however with bleeds off I get flex thrust.(splitting hair you might say:O ). Now can I choose to use flex t/o and if I loose an engine choose not to select TOGA (time limted) and continue on flex thrust to reach msa to clr a distant obst with out having to worry about time?

First, I do not thing it is splitting hair. It has economical benefits - saves engine life. Should your engine be ready to call it a day, running it at less RPM may just make the difference between make or break. Also, should you have any emergency of any kind, your extra thrust is readily available to you where you look for it - thrust levers, not overhead on bleed switches.

For the second part the answer is YES/NO.

Yes for not using TOGA. When performace is calculated on use of less than full tkof thrust (this thrust is normally still above Max Continious - id est still above Max unlimited) there is no need to select full thrust to achieve the calculated obstacle clearance. Simply, the calculation does not account for re-selecting TOGA, so you do not have to. If you want it, it is all yours to use! But give it a thought beforehand, if your ship is stabilized, climbing steadily, in trim, possibly with AP on and failed engine secured it is a good call. On the other hand if the initial thrust reduction was rather large, selecting TOGA will introduce an extra amount of adverse yaw. During initial moments, this may outweigh the benefits of added thrust both handling-wise (perceived increase in Vmca) and performance-wise (spoilers extended if not handled correctly).

NO for keeping the albeit reduced power indefinitely. Yes, TOGA is limited for 5 mins and 10 with one engine out (or any other number and rule be the book). But unlimited operation is only guaranteed at much lesser power settings CON/MCT - maximum continious/nominal. In the scenario you describe (and 99 day to day ops), the takeoff thrust you selected for departure, is still above MCT hence it may not be used indefinitely. Perhaps the engine run ok for, say 17 minutes, but there is no way we would know, so we must not. The manufacurer's rules are clear as well: operation above MCT is restricted to max 5/10/.... minutes (my wording). Your performance calculations included reduced thrust for the prescribed time only. There is no need to do more.

FD
(the un-real)

FlightDetent, thank you for that post it helped to clear up the cobwebs:)
happy landing and tailwinds all the time

This is a wrong reasoning Why?
Because if you had an engine failure on take off and if you ask yourself how long time you can set FLEX N1, that means that the position of your aircraft on vertical profil is critical. Well then don't worry to much and set TOGA then you'll get an extra 10 minutes to get you out of the bush.
In other word you will be setting TOGA before having to ask yourself how long can I stay in that position. Sometimes don't think to much be basic

One needs to keep in mind that nothing comes free in this life. The following has been stated/inferred previously in the thread but needs to be keep in mind ..

(a) the Design Standards require that power need not be adjusted during the takeoff

(b) a flex takeoff is calculated with that level of thrust and a failure ought not to cause a great concern from the point of thrust considerations

(c) there is nothing to preclude a concerned pilot from increasing thrust following a failure. However, this adds to the handling problems and, depending on the aircraft/engine characteristics, may present you with a very significant problem. Quite some years ago I was involved in an accident investigation relating to a fatal in which the crew very likely were caught out by too much thrust asymmetry following a failure with quite confusing indications .. Vmca departure and no survivors.


While the need for thinking pilots will remain ... too much innovative thought can bite if it is not backed up by the appropriate level of manipulative skill and systems knowledge.

thanks
 

Hello everybody,
thank you all for the response. wishing all tailwinds and happylandings all the time;)