Use of MCT on A320 family during CLIMB
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By definition there should be no time limit on the use of MCT. Do any of you folk think the engine manufacturer is going to publish a Max Continuous Thrust Limit which is time limited? Or am I just expressing the practical opinion of an old Flight Engineer?
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I've often thought about the fact that technically speaking there is absolutely no limit on the amount of time MCT can be used (by definition).
But above about FL200 it's the same as TOGA.
You are limited to 5 mins with TOGA (two engines). So if you just move it that one notch further....... no change in thrust but technically now time limited. 😬
But above about FL200 it's the same as TOGA.
You are limited to 5 mins with TOGA (two engines). So if you just move it that one notch further....... no change in thrust but technically now time limited. 😬
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MCT - TOGA
I guess terminology can sometimes be confusing and I appreciate that there is no longer aeroplanes being built which carry Flight Engineers. As one of those dinosaurs of the past, to my mind, even considering TOGA in the example cited i.e., at Flight Levels above FL200, makes no sense. My understanding of TOGA is that it is a thrust setting which may be used for Take Off and/or Go Around for a limited time. That the MCT and TOGA thrust available are one and the same above FL200 is not a surprise to me. Common sense would dictate that TOGA Thrust Lever position at those levels is simply another position which if selected makes no difference to thrust produced and therefore, if selected for some obscure reason, MCT limits would apply.
But above about FL200 it's the same as TOGA.
You are limited to 5 mins with TOGA (two engines). So if you just move it that one notch further....... no change in thrust but technically now time limited. 😬
You are limited to 5 mins with TOGA (two engines). So if you just move it that one notch further....... no change in thrust but technically now time limited. 😬
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Love being devils advocate! You're correct if we take it at face value but as old fella quite rightly says, they are really referring to low altitude.
Some very experienced pilots haven't necessarily considered this fact as they seem perplexed for a short while when you tell them.
AF447 - The thrust levers were put into TOGA detent numerous times.
I can't help thinking that they expected a large thrust response. If you think about it, we only see TOGA at low altitude for go around (same in the simulator). We've been conditioned into expecting a large thrust response..... but if your above 200 you aren't going to get it!
Some very experienced pilots haven't necessarily considered this fact as they seem perplexed for a short while when you tell them.
AF447 - The thrust levers were put into TOGA detent numerous times.
I can't help thinking that they expected a large thrust response. If you think about it, we only see TOGA at low altitude for go around (same in the simulator). We've been conditioned into expecting a large thrust response..... but if your above 200 you aren't going to get it!
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From FCOM as quoted before:
It is unambiguous. Only thing that comes to my mind is, they can't be serious. Nobody seems to care about it neither pilots nor the airlines. What is the compulsion that makes them insert this?
It is the maximum thrust certified for continuous use. This rating should be used, at the pilot’s discretion, only when required to ensure safe flight (engine failure).
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Guys, be careful when using MCT during normal operations.
I knew a captain in my company who used to sometimes use TOGA thrust during takeoff for the sake of it. Then one day when LVR CLB flashed, he pulled it back one detent (instead of two) and didn't realise. MCT on climbout and ended up busting the speed constraint. He got called into the office and was chewed out.
I knew a captain in my company who used to sometimes use TOGA thrust during takeoff for the sake of it. Then one day when LVR CLB flashed, he pulled it back one detent (instead of two) and didn't realise. MCT on climbout and ended up busting the speed constraint. He got called into the office and was chewed out.
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I would approach this question from another angle.
If you perform a takeoff at low weights what N1 do you get when you select CLB versus doing a takeoff at higher weights assuming all other conditions remain the same?
I've been off the 320 for a while now but if my memory serves me correct the CLB thrust is different depending on the weight? Am i right in saying this?
On the widebody airbuses you can select a derated climb. However, without moving the thrust levers you can always switch to maximum climb thrust using the FMS, and this will give you an N1, in some cases, around 25% higher than the derated case. It's great when ATC asks you to expedite.
So on the narrow-body busses with no option to select a derated climb am i right in assuming the aircraft is always choosing a derated climb given the weights? Or is it always targeting maximum climb thrust. I'm sure that at various weights we had different climb thrusts?
Now coming back to the derated climb Vs normal climb thrust on the wide bodies. I'm not sure if the Max CLB thrust is the same as MCT but it must be darn close because it is pretty high. So I'm wondering why we get that option in the big busses but on the narrow bodies we are left with either the calculated CLB thrust or MCT.
And looking at my 320 FCOM it says specifically that MCT is to be used at pilots discretion but in parenthesis says 'single engine'. Which is seriously confusing because you wonder if that is an example case or a restriction.
If you perform a takeoff at low weights what N1 do you get when you select CLB versus doing a takeoff at higher weights assuming all other conditions remain the same?
I've been off the 320 for a while now but if my memory serves me correct the CLB thrust is different depending on the weight? Am i right in saying this?
On the widebody airbuses you can select a derated climb. However, without moving the thrust levers you can always switch to maximum climb thrust using the FMS, and this will give you an N1, in some cases, around 25% higher than the derated case. It's great when ATC asks you to expedite.
So on the narrow-body busses with no option to select a derated climb am i right in assuming the aircraft is always choosing a derated climb given the weights? Or is it always targeting maximum climb thrust. I'm sure that at various weights we had different climb thrusts?
Now coming back to the derated climb Vs normal climb thrust on the wide bodies. I'm not sure if the Max CLB thrust is the same as MCT but it must be darn close because it is pretty high. So I'm wondering why we get that option in the big busses but on the narrow bodies we are left with either the calculated CLB thrust or MCT.
And looking at my 320 FCOM it says specifically that MCT is to be used at pilots discretion but in parenthesis says 'single engine'. Which is seriously confusing because you wonder if that is an example case or a restriction.
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Getting back to the original question. CMpilot1 is of the opinion that MCT should be used only in abnormal operations. Putting aside all the various options mentioned to date I repeat my question. Does anyone think the engine manufacturer is going publish a Maximum CONTINUOUS Thrust which they believe will be detrimental to the engine? I think not. Different operators have different approaches as to how they wish their aircraft to be operated. If the engine manufacturer says the MCT is X, then you should expect that thrust setting may be used unlimited (for as long as desired/required). COUGH asks about engine wear in relation to the use of MCT. In many cases MCT and CLMB will be the same. Where MCT is higher than CLMB, and CLMB is used the time to climb will be greater than that if MCT were used. Engines remember RPM, Time and EGT and where MCT is higher than CLMB there will likely be some reduction in the service life of the engine. How significant this is is dependent on how much higher the RPM and EGT are for MCT v CLMB. If any particular operator wishes to impose a limit on MCT use they should explain the reasons why.
Last edited by Old Fella; 15th Apr 2017 at 06:13. Reason: Additional comment.
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Come on! It's quite simple. CLB1 and CLB2 are there mostly to reduce engine wear. With MCT you will not bust limitations but more significantly reduce engine life if use it frequently. So, go ahead, if you really need it, but don't make it a habit. Once you start using it with no safety reason there will be nothing to limit your desire to get the aicraft to it's cruising level faster and call for coffee
Last edited by Romasik; 16th Apr 2017 at 08:09.
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There is a definitely a catch. The FCOM has clearly stated and the onus is on the user. The sluggish climb and clearing by skin of teeth is all subjective as people have even vehemently opposed the use of TOGA in EFATO scenario where very accurate flying is required to achieve the certification performance. Quoted below from an old thread:
barit1 8th Oct 2008, 22:57
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 accelerated 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 bean counters, make the decision that's right for your airline, but don't let safety worry you.
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 accelerated 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 bean counters, make the decision that's right for your airline, but don't let safety worry you.
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FCOM PER-THR-MCT is crystal clear :
DEFINITION
Applicable to: ALL
It is the maximum thrust certified for continuous use. This rating should be used, at the pilot’s discretion, only when required to ensure safe flight (engine failure).
so only use MCT at engine failure !
DEFINITION
Applicable to: ALL
It is the maximum thrust certified for continuous use. This rating should be used, at the pilot’s discretion, only when required to ensure safe flight (engine failure).
so only use MCT at engine failure !
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Don't take all Airbus words at face value. There are numerous examples when their writing is ambiguous. Look at your own phrase. It says "at the pilot's discretion". MCT is not a discretion when engine fails. It's an established procedure. (Engine failure) in brackets looks like an example, not a single case of MCT usage. Otherwise it should have been written "to ensure safe flight in case of an engine failure". Everybody reads what he wants to read. The same words.
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Boeing also says MCT is for use only in emergency.
Now what constitutes an emergency surely not ATC requirements or boredom with existing climb rate. That's why without SOP guidelines/company policy (if you like) the argument will never end.
Now what constitutes an emergency surely not ATC requirements or boredom with existing climb rate. That's why without SOP guidelines/company policy (if you like) the argument will never end.