View Full Version : mct on AIRBUS

7th Oct 2008, 09:06
My question is... to achieve your level.... incase of atc request or to pass a level incase of turbulance...
can mct thrust be used?? Its got no time limit...
I neutral with this opinion.. wanted to know wht do u'll think about it.

flying finn
7th Oct 2008, 09:25
This is what FCOM 3.05.06 P1 has to say about it (for the A320).
Maximum continuous
It is the maximum thrust certified for continuous use. This rating should be used, at the pilotís discretion, only when required to ensure safe flight (engine failure).

...so a little vague as usual. Wouldn't use it myself to meet an ATC restriction; I'd have thought winding back the climb speed would have a more significant effect.

Gary Lager
7th Oct 2008, 09:38
At high altitude MCT thrust and CLB thrust are pretty much the same, so there's no advantage.

My advice is if you are concerned about ATC restrictions or rates of climb, use the EXP pb or selected speed.

7th Oct 2008, 11:33
MCT only used in emergency cases as per airbus , mostly in 1 eng out situations , was a discussion the other day about how at lower levels to meet a constraint one could in theory use MCT to get that extra juice

but on the 30 there is no EXP button as is the case on the 20 so winding down speed down to Green Dot seems to be the best way to go , also really depends on your ISA dev at that point

7th Oct 2008, 18:00
Or just go to TOGA as I heard one idiot did some time ago in the Far East!!

8th Oct 2008, 12:02
Gary Lager and Sidstar.

I think you will find that at high level Climb power. MCT and TOGA are in
fact the same.

So if you move the levers from Climb to MCT and on to TOGA there is
no change in N1


8th Oct 2008, 12:05
Yup, agreed. Shown to me in-flight by a training captain. Went to TOGA during climb at high altitude. Zero change in engine parameters.

Gary Lager
8th Oct 2008, 15:22
Isn't that what I said? Duh!

Dan Winterland
8th Oct 2008, 16:00
My company's 320s don't have EXP pushbuttons. They are an option.

Conan The Barber
8th Oct 2008, 16:07
I suppose people can define "high altitude/level"? At what altitude is TOGA=MCT=CL?

Or are people just guestimating and accepting the resulting decrease in engine life as a minor inconvenience?

8th Oct 2008, 18:27
From an old engineman's perspective -

Max CLB is a OEM warranty rating, and NOT a certification point. At some conditions, notably TOC, CLB and MCT may in fact converge.

But MCT is not a safety issue at all; It's a matter of warranty coverage by the OEM. If your FDR shows untoward MCT usage, your airline may have trouble collecting on parts life warranty.

For years, I did repeated ground testing of big fans in which we acceled slowly to MCT, held 5 minutes for thermal stabilization, then ran 30 min. or more at various TO ratings before retarding below MCT. I can show you over 100 hrs. experience doing this testing on one engine. There was never a mechanical reliability issue, although some performance falloff naturally occurred.

So it's strictly the Captain's choice; you trade off increased deterioration (which means more fuel burned over the on-wing engine life) vs making a FL "gate". Talk it over with your beancounters, make the decision that's right for your airline, but don't let safety worry you.

8th Oct 2008, 20:01
thnks Barit...
ur opinion pretty much answers my query...

8th Oct 2008, 21:07
As stated above, at high altitude, TOGA, MCT and CLB are all the same value.

This should come as no surprise to anyone because it is clearly indicated on your engine instruments.

The thrust lever position is indicated by the donuts on the EPR or N1 scale (EPR or N1 depends on which engine is installed).
The normal position of the thrust levers is in the CLB detent, so the donuts indicate CLB.
The absolute maximum thrust that the engine can deliver under present conditions is indicated by the yellow tic marks on the same (EPR or N1) scale. TOGA would be at that absolute maximum. The yellow tic marks are provided by the EECs, not by the thrust management computer. As each EEC has two channels, what you see as one tic mark per engine, are actually two tic marks, overlaying each other.
MCT would be somewhere between CLB and TOGA, the actual value would only become visible, as you would move the thrust levers into the MCT detent, the donuts would then indicate MCT.
(For the IAE 2500 engines) As long as you are below 25.000 ft, the yellow tic marks are beyond the donuts by a fairly wide margin.
When climbing from (approximately) 25.000 to 27.000 ft, you can see the yellow tic marcs creep back towards the donuts, above 27.000 ft the yellow tic marks overlay the donuts, so advancing the thrust levers into the MCT detent or even towards the forward stop will not give you anything more than CLB already gave you.

Edited for a typo

9th Oct 2008, 15:51
Aren't you missing the point here, I would not overboost, or reduce my company's equipment life to satisfy ATC.

Simply advise you are unable and take a vector.

MCT is for single engine work.

9th Oct 2008, 16:07
Barit1, thanks for that insight. Very usefull.

Still, imho you come to the wrong conclusion. Because it IS the same, and it doesn't damage your engine (too much), you shouldn't use MCT or even TOGA.

We as pilots are not only liable towards the bean counters and the ATC, but to our procedures. Under chapter limitations you have a limited time of TOGA. MCT is per definition the maximum thrust setting you are continously allowed to. So if you go over the limitations, you act against the rules and can be sued.

And it doesn't show good airmanship if you use all your reserves just to satisfy ATCs requirements or your ego in case you want to outclimb someone else. Reserves are there to be kept until you really really need them. No ATC controller will thank you if you get into trouble and you tell him "I just wanted to help you".


10th Oct 2008, 08:28
between 26500 and 26800 if you look closely it will become 0 diff.