A320 TOGA Efficiency
 

Hi folks,
First of all I would like to apologies for asking this silly question. But it just keep bothering me.
I am wondering at what Flight Level or Altitude TOGA Thrust will be in-efficient? Since I could not find the answer on FCOM
As EXP CLIMB it stated it's not recommended to use that mode after passing FL 250 (If I am not mistaken).

Thanks for your help guys.

What You are asking is not very clear, at least for me. Are You asking how much does thrust decrease with increasing altitude and its effects on rate of climb or something like that ?

Apology sonicbum, what I am trying to ask is in high altitude will there any significant impact if I required more thrust by setting to TOGA in order to gain more rate of climb.

Short answer : absolutely no. For a detailed answer we need some data from the engine and examine the thrust output variations graph according to all the different parameters taken into account by the FADEC.

What circumstances would require you to need extra thrust?

To gain extra ROC you can trade airspeed/Mach for a (short) while. Anything else could and maybe should require a call to ATC saying 'unable' or a request for descent.

Thanks for your info

TopBunk at this point I only come out from scenario that I am accidentally flying into a missile area where I have to reach certain Altitude to avoid those missile. For example I am cruize at FL 290, and as per notam Minimum flying is FL 360, where deviate is not an option.

Sorry for the confusion, I am just curious. Not planning to experience it in real life.

A u-turn would be an easier option...

Although expedite climb is not recommended, if you desperately want to get height quickly it's likely the best option as it'll trade all your excess energy for altitude.

I think you might be misjudging the severity of the notam though, which is really for discouraging routine flight within missile range. After all, if you had a depressurisation or engine failure you're going to end up down there anyway.

Perhaps the question can be rephrased.

What is the limiting altitude, where the engine is no longer capable to provide any more than MAX CLB thrust, and so moving the thrust levers beyond the CLB detent yields no reaction?

Top of my head, I do not know. The feeling is maybe as low as FL170, but that's just a shot in the dark. It had been discussed before.

It varies a bit between different aircraft and engine types, but the takeoff envelope is typically defined up somewhere between 15k and 18k, and airspeed up to around Mach 0.5. Go faster than that, and/or higher than that, and pushing the throttles beyond max climb doesn't do anything.

Thanks FlightDetent

tdracer thanks for more detail info.
Appreciate it.

tdracer
Is it beyond CLB or beyond MCT because as you know when with OEI thrust levers are pushed to MCT.

At least on all the engines I'm familiar with, MCT is never above max CLB. Usually, at somewhere around 30k, MCT becomes the same max CLB, below that MCT is a bit less. So out of the takeoff envelope, max climb is as good as it's going to get.

Not sure what you really meant to say there, but MCT is the maximum rated thrust outside of the conditions under which the time-limited takeoff thrust is available. Max climb can't be higher than the maximum rated thrust. Did you mean max clb at the end of your second sentence and in your third sentence? Am I missing something?

Whoops, yes I misspoke (misswrote?). Climb is not always higher than Con - I was thinking of something else.
However at altitude (usually above 30k), Max Con and Max Climb are typically the same thing.

Thus, in response to vilas:

above 15-17k - the engine would typically not deliver more than MAX CON
above 30-ish k - the engine would typically not deliver more than MAX CLB

correct?