It is fairly standard knowledge that in dry or normal weather, takeoffs are derated, but what about snow or icy weather? Are takeoffs still derated? I have heard that some airlines specifically prohibit derated takeoffs when the runway is contaminated in such a manner.

Are you asking about “derate”or “reduced thrust” (assumed temp method)? Two different things. Usually reduced thrust is prohibited on contaminated runways, but a derate might well help things.

GF

To echo what GF said, reduced thrust is generally forbidden if there is contamination on the runway. Airlines which I have worked for have defined contanination if it is reported on the ATIS. Then it is a full thrust take off.

However, there are times when you can do a derated thrust takeoff and actually get more payload off than you could do a full thrust takeoff. Just going back in my cobweb filled mind, there are certain on the 747 classic and 747-400, where you could use -3A power to compute the takeoff data on a contaminated runway. By comparing full thust to derated thrust you could see there was an increase in payload on the reduced thrust takeoff.

Having done engine out ferries, we would also use 3A thrust on the 400 when doinig engine out ferries for more conservative takeoff performance.

mmo wrote:

To echo what GF said, reduced thrust is generally forbidden if there is contamination on the runway. Airlines which I have worked for have defined contanination if it is reported on the ATIS. Then it is a full thrust take off.

However, there are times when you can do a derated thrust takeoff and actually get more payload off than you could do a full thrust takeoff. Just going back in my cobweb filled mind, there are certain on the 747 classic and 747-400, where you could use -3A power to compute the takeoff data on a contaminated runway. By comparing full thust to derated thrust you could see there was an increase in payload on the reduced thrust takeoff.

Having done engine out ferries, we would also use 3A thrust on the 400 when doinig engine out ferries for more conservative takeoff performance.

I heard that recently too, but it’s counterintuitive. Not sure I get it yet. I’m well aware of the differences between an Assumed Temperature reduction and Fixed Derate. Can you please explain why a Fixed Detate could allow you to actually carry more payload? Thanks.

By reducing thrust thru the derate, the Vmcg and/or Vmca is reduced allowing for lower V1, Vr and V2 speeds. Think of a derate as installing a different engine on the wing with different speeds. Lower speeds means reduced distances or, better yet, greater loads off a fixed distance i.e. a defined runway.

An ATM reduction is limited by full rated thrust Vmcg and Vmca.

GF

GalaxyFlyer wrote:

By reducing thrust thru the derate, the Vmcg and/or Vmca is reduced allowing for lower V1, Vr and V2 speeds. Think of a derate as installing a different engine on the wing with different speeds. Lower speeds means reduced distances or, better yet, greater loads off a fixed distance i.e. a defined runway.

An ATM reduction is limited by full rated thrust Vmcg and Vmca.

GF

Thanks. I think I get it now. We had another thread on takeoff and climb derates recently. A fixed derate is basically a limit. The Boeing manuals state to not increase thrust above your derate setting unless it's an emergency and ground contact is imminent.

Yes, because by increasing thrust in the OEI case, if the airspeed is below Vmcg or Vmca, the pilot could lose control due to asymmetric thrust. Think of Vmcg and Vmca as redlines below which you must not go in asymmetric conditions and you won’t know where you are in relation to them when increasing thrust above rated power.

gf

GalaxyFlyer wrote:

Yes, because by increasing thrust in the OEI case, if the airspeed is below Vmcg or Vmca, the pilot could lose control due to asymmetric thrust. Think of Vmcg and Vmca as redlines below which you must not go in asymmetric conditions and you won’t know where you are in relation to them when increasing thrust above rated power.

gf

Right. I'm familiar with it. Of course it's only a factor if an engine fails.

There was an extensive threads on derates/reductions recently. I chimed in on what the various Boeing models have in this regard. I know Airbus has Flex (Assumed Temperature) thrust reductions. Do they also have fixed derates?

Quoting BoeingGuy (Reply # 8), " . . . Airbus has Flex (Assumed Temperature) thrust reductions. Do they also have fixed derates?"

BoeingGuy, I have seen previously from reading another thread that on the Airbus narrowbody series (A319/A320/A321) with CFM56-5A5, CFM56-5-A1 and A3, and CFM56-5B3/3, they do not use derate, only flex.

e38

e38 wrote:

Quoting BoeingGuy (Reply # 8), " . . . Airbus has Flex (Assumed Temperature) thrust reductions. Do they also have fixed derates?"

BoeingGuy, I have seen previously from reading another thread that on the Airbus narrowbody series (A319/A320/A321) with CFM56-5A5, CFM56-5-A1 and A3, and CFM56-5B3/3, they do not use derate, only flex.

e38

That is not true, Airbus FBW do have derate, instead of putting in say F40 for flex 40 on thectajeoff performance pace you put in D24 for the derate.

In the operations I’ve seen: no. Full thrust takeoff with any runway contamination.

mmo wrote:

However, there are times when you can do a derated thrust takeoff and actually get more payload off than you could do a full thrust takeoff. Just going back in my cobweb filled mind, there are certain on the 747 classic and 747-400, where you could use -3A power to compute the takeoff data on a contaminated runway. By comparing full thust to derated thrust you could see there was an increase in payload on the reduced thrust takeoff.

I know this is a bit tangential, but can you explain how that works?

zeke wrote:

e38 wrote:

Quoting BoeingGuy (Reply # 8), " . . . Airbus has Flex (Assumed Temperature) thrust reductions. Do they also have fixed derates?"

BoeingGuy, I have seen previously from reading another thread that on the Airbus narrowbody series (A319/A320/A321) with CFM56-5A5, CFM56-5-A1 and A3, and CFM56-5B3/3, they do not use derate, only flex.

e38

That is not true, Airbus FBW do have derate, instead of putting in say F40 for flex 40 on thectajeoff performance pace you put in D24 for the derate.

Sound like it works more like the 737 than other Boeing models. Sounds like you are selecting an actual derated rating like 24,000 lbs. The other models just select a percentage derate, usually 10% and 20%.

DocLightning wrote:

mmo wrote:

However, there are times when you can do a derated thrust takeoff and actually get more payload off than you could do a full thrust takeoff. Just going back in my cobweb filled mind, there are certain on the 747 classic and 747-400, where you could use -3A power to compute the takeoff data on a contaminated runway. By comparing full thust to derated thrust you could see there was an increase in payload on the reduced thrust takeoff.

I know this is a bit tangential, but can you explain how that works?

It has been a while since I have had to teach performance, but here it goes.

The problem with contamination is directional control due to the poor conditions on the runway. With higher thrust engines you have, or potentially have a problem with directional control with the contamination and the high thrust. Thus you could be in a situation of having to get a lower weight to compensate for the VMCA/VMCG problem. So, if you have a PW powered aircraft or GE, you can do a derated thrust. I don't know what the 747-8 derate would be but most likely some derivative of the CF60, but on the PW4000, you can go down to JT9D-3A thrust settings. So, that allows a lower V1 Vr and V2 due to the decreased thrust and the diminished problem of excess thrust.

On 3 engine takeoffs on the 744, we would, in the case of #1 being inop, use PW4000 thrust settings on 2 & 3 while using -3A thrust settings on 4. That way, you have less asymmetrical thrust to deal with. Once cleaned up, then you can use 4000 normal thrust settings.

Hope that makes sense.

mmo wrote:

Hope that makes sense.

It does. Thank you!

mmo wrote:

DocLightning wrote:

mmo wrote:

However, there are times when you can do a derated thrust takeoff and actually get more payload off than you could do a full thrust takeoff. Just going back in my cobweb filled mind, there are certain on the 747 classic and 747-400, where you could use -3A power to compute the takeoff data on a contaminated runway. By comparing full thust to derated thrust you could see there was an increase in payload on the reduced thrust takeoff.

I know this is a bit tangential, but can you explain how that works?

It has been a while since I have had to teach performance, but here it goes.

The problem with contamination is directional control due to the poor conditions on the runway. With higher thrust engines you have, or potentially have a problem with directional control with the contamination and the high thrust. Thus you could be in a situation of having to get a lower weight to compensate for the VMCA/VMCG problem. So, if you have a PW powered aircraft or GE, you can do a derated thrust. I don't know what the 747-8 derate would be but most likely some derivative of the CF60, but on the PW4000, you can go down to JT9D-3A thrust settings. So, that allows a lower V1 Vr and V2 due to the decreased thrust and the diminished problem of excess thrust.

On 3 engine takeoffs on the 744, we would, in the case of #1 being inop, use PW4000 thrust settings on 2 & 3 while using -3A thrust settings on 4. That way, you have less asymmetrical thrust to deal with. Once cleaned up, then you can use 4000 normal thrust settings.

Hope that makes sense.

Great explaination but that’s not how derates work on Non-737 Boeing airplanes. You don’t select another engine’s thrust rating. You select the TO 1 or TO 2 fixed percentage derates. They are preset and most often 10% and 20% derates. Is the -3A approximate to one of these?

EDIT: Out if curiousity I’ll look up the 747-400. I don’t know the 747 as well. What I described is how it works on 777, 787, and 757 and 767 that are equipped with fixed derates. I thought the 747 is the same though.

BoeingGuy wrote:

mmo wrote:

DocLightning wrote:

I know this is a bit tangential, but can you explain how that works?

It has been a while since I have had to teach performance, but here it goes.

The problem with contamination is directional control due to the poor conditions on the runway. With higher thrust engines you have, or potentially have a problem with directional control with the contamination and the high thrust. Thus you could be in a situation of having to get a lower weight to compensate for the VMCA/VMCG problem. So, if you have a PW powered aircraft or GE, you can do a derated thrust. I don't know what the 747-8 derate would be but most likely some derivative of the CF60, but on the PW4000, you can go down to JT9D-3A thrust settings. So, that allows a lower V1 Vr and V2 due to the decreased thrust and the diminished problem of excess thrust.

On 3 engine takeoffs on the 744, we would, in the case of #1 being inop, use PW4000 thrust settings on 2 & 3 while using -3A thrust settings on 4. That way, you have less asymmetrical thrust to deal with. Once cleaned up, then you can use 4000 normal thrust settings.

Hope that makes sense.

Great explaination but that’s not how derates work on Non-737 Boeing airplanes. You don’t select another engine’s thrust rating. You select the TO 1 or TO 2 fixed percentage derates. They are preset and most often 10% and 20% derates. Is the -3A approximate to one of these?

EDIT: Out if curiousity I’ll look up the 747-400. I don’t know the 747 as well. What I described is how it works on 777, 787, and 757 and 767 that are equipped with fixed derates. I thought the 747 is the same though.

Thanks for the comments, but I did not reference the 737 at all. Any inference to how that works is on you and not an error on my part. Of my 23,000 hours over 15,000 is on the 747 family, from the SP through the 400. I might be dumb but I am not stupid and I will not talk about things (737) I have no knowledge of. Having flown the 777/787 I do remember the fixed derates but don't consider the performance issues with a contaminated runway that complex on those aircraft.

The 744 is also equipped with the fixed derates like you write. However, on the PW powered aircraft, you always had the option of going into the performance books and get the -3A power performance. I assume those were available to purchase or get depending on the package purchased by the airline. While the option to set a 10/20% derate, the -3A power is a EPR setting which is set manually. It would be more than 20% IIRC. All the operators I have worked for have the -3A performance on all their aircraft, from the SP through the 400.

BoeingGuy wrote:

Sound like it works more like the 737 than other Boeing models. Sounds like you are selecting an actual derated rating like 24,000 lbs. The other models just select a percentage derate, usually 10% and 20%.

When derated takeoff is available, 6 certified levels exist, ranging from D04 (TOGA-4%) to D24 (TOGA–24%) with a constant four percent increment (4%, 8%, 12%, 16%, 20% and 24%) is on all FBW Airbus. The larger aircraft can go as high as a 40% derate.

mmo wrote:

BoeingGuy wrote:

mmo wrote:

It has been a while since I have had to teach performance, but here it goes.

The problem with contamination is directional control due to the poor conditions on the runway. With higher thrust engines you have, or potentially have a problem with directional control with the contamination and the high thrust. Thus you could be in a situation of having to get a lower weight to compensate for the VMCA/VMCG problem. So, if you have a PW powered aircraft or GE, you can do a derated thrust. I don't know what the 747-8 derate would be but most likely some derivative of the CF60, but on the PW4000, you can go down to JT9D-3A thrust settings. So, that allows a lower V1 Vr and V2 due to the decreased thrust and the diminished problem of excess thrust.

On 3 engine takeoffs on the 744, we would, in the case of #1 being inop, use PW4000 thrust settings on 2 & 3 while using -3A thrust settings on 4. That way, you have less asymmetrical thrust to deal with. Once cleaned up, then you can use 4000 normal thrust settings.

Hope that makes sense.

Great explaination but that’s not how derates work on Non-737 Boeing airplanes. You don’t select another engine’s thrust rating. You select the TO 1 or TO 2 fixed percentage derates. They are preset and most often 10% and 20% derates. Is the -3A approximate to one of these?

EDIT: Out if curiousity I’ll look up the 747-400. I don’t know the 747 as well. What I described is how it works on 777, 787, and 757 and 767 that are equipped with fixed derates. I thought the 747 is the same though.

Thanks for the comments, but I did not reference the 737 at all. Any inference to how that works is on you and not an error on my part. Of my 23,000 hours over 15,000 is on the 747 family, from the SP through the 400. I might be dumb but I am not stupid and I will not talk about things (737) I have no knowledge of. Having flown the 777/787 I do remember the fixed derates but don't consider the performance issues with a contaminated runway that complex on those aircraft.

The 744 is also equipped with the fixed derates like you write. However, on the PW powered aircraft, you always had the option of going into the performance books and get the -3A power performance. I assume those were available to purchase or get depending on the package purchased by the airline. While the option to set a 10/20% derate, the -3A power is a EPR setting which is set manually. It would be more than 20% IIRC. All the operators I have worked for have the -3A performance on all their aircraft, from the SP through the 400.

If you read what I wrote, I said I was referring to NON-737 models. I other worlds I was describing how models OTHER than the 737 work.

However, now that you explain it, I see you were using the MAN takeoff setting. You were manually entering in a target EPR.

I had actually forgotten for a moment that selection exists too. I didn’t think it was commonly done. You go to the CDU and type in your target takeoff thrust. That is a baseline feature, not option.

GalaxyFlyer wrote:

Are you asking about “derate”or “reduced thrust” (assumed temp method)? Two different things. Usually reduced thrust is prohibited on contaminated runways, but a derate might well help things.

Can you explain the difference to me? Back in my day, we wanted all the thrust we could get out of those old J57s...

A derate is like installing an engine with different ratings. It’s a selection in the FMS that tells the FADEC to limit thrust to a fixed percentage below the installation’s full rating. 10% and 20% derate being a common option, but as noted could be different, operator option. The modern planes usually, especially twins, have an abundance of thrust and reducing the rating allows for lowering Vmcg and Vmca.

Reduced (aka flex) assumes a higher than ambient temperatures being used to set power and performance. When less than rated power is needed to met the required performance on a take-off, using an assumed higher temp lowers the thrust. Full thrust is available, if needed. Using reduced or derate or a combination of the two reduces engine wear. 20,000 hours plus “on the wing” is very common now with modern on condition maintenance.

GF

BoeingGuy wrote:

However, now that you explain it, I see you were using the MAN takeoff setting. You were manually entering in a target EPR.

I had actually forgotten for a moment that selection exists too. I didn’t think it was commonly done. You go to the CDU and type in your target takeoff thrust. That is a baseline feature, not option.

If you are dealing with a contaminated runway, you would do it through the CDU. For an engine out ferry situation, you did it the "old fashioned way" by manually setting the thrust levers.

GalaxyFlyer wrote:

Thanks, GF! So it sounds like the same outcome - less thrust out the back - but with two different approaches to achieve it.

zeke wrote:

BoeingGuy wrote:

Sound like it works more like the 737 than other Boeing models. Sounds like you are selecting an actual derated rating like 24,000 lbs. The other models just select a percentage derate, usually 10% and 20%.

When derated takeoff is available, 6 certified levels exist, ranging from D04 (TOGA-4%) to D24 (TOGA–24%) with a constant four percent increment (4%, 8%, 12%, 16%, 20% and 24%) is on all FBW Airbus. The larger aircraft can go as high as a 40% derate.

If you select a fixed derate on a FBW Airbus, how do you set thrust for takeoff? Do you put the thrust levels in the second detent - before full TO/GA - just like you do for Flex Power? The only difference is what takeoff thrust setting you selected in the FMC?

I think I have a little understanding of how the Airbus Autothrust system works. I thought there are different detents that you put the thrust levers in for TO/GA, Flex, Climb, Cruise, and Retard. Is that right?

BoeingGuy wrote:

If you select a fixed derate on a FBW Airbus, how do you set thrust for takeoff? Do you put the thrust levels in the second detent - before full TO/GA - just like you do for Flex Power? The only difference is what takeoff thrust setting you selected in the FMC?

Exactly the same as Fkex, instead of putting eg F50 in the FMC, you put in D20, move the thrust levels same detenti as flex. The actual thrust limit that is being performed by the engine is displayed on the EWD, TOGA/Flex etc.

The mode on the FMA when thrust is being set at the start of the takeoff roll will also tell you TOGA, Fkex. Derate

BoeingGuy wrote:

zeke wrote:

BoeingGuy wrote:

Sound like it works more like the 737 than other Boeing models. Sounds like you are selecting an actual derated rating like 24,000 lbs. The other models just select a percentage derate, usually 10% and 20%.

When derated takeoff is available, 6 certified levels exist, ranging from D04 (TOGA-4%) to D24 (TOGA–24%) with a constant four percent increment (4%, 8%, 12%, 16%, 20% and 24%) is on all FBW Airbus. The larger aircraft can go as high as a 40% derate.

If you select a fixed derate on a FBW Airbus, how do you set thrust for takeoff? Do you put the thrust levels in the second detent - before full TO/GA - just like you do for Flex Power? The only difference is what takeoff thrust setting you selected in the FMC?

I think I have a little understanding of how the Airbus Autothrust system works. I thought there are different detents that you put the thrust levers in for TO/GA, Flex, Climb, Cruise, and Retard. Is that right?

To clarify the Airbus thrust lever detents, there are four:
- TOGA.
- FLEX/MCT. Max Continuous Thrust. In the take-off phase, this detent is used for FLEX or derated thrust.
- CLB. Max climb thrust. If autothrust is active, this detent is used for climb (after thrust reduction), cruise, descent and approach.
- Idle. When the plane tells you to retard, this is the detent it wants. The reversers can only be pulled with the thrust levers in idle.

Moose135 wrote:

GalaxyFlyer wrote:

Are you asking about “derate”or “reduced thrust” (assumed temp method)? Two different things. Usually reduced thrust is prohibited on contaminated runways, but a derate might well help things.

Can you explain the difference to me? Back in my day, we wanted all the thrust we could get out of those old J57s...

As explained above, directional control on a contaminated runway is the critical factor. If you're on all engines, it's all good since thrust is symmetrical. If you lose an engine, however, the derate gives a lower VMC, enabling you to climb out safely.

Operationally, if you use FLEX (assumed temperature) you may go to TOGA at any time since there is a margin to VMC. If you use Derate, you may not go to TOGA because the extra thrust on one engine could exceed the directional control ability of the aircraft.

Thanks for that additional clarification, Starlionblue.

Starlionblue wrote:

To clarify the Airbus thrust lever detents, there are four:
- TOGA.
- FLEX/MCT. Max Continuous Thrust. In the take-off phase, this detent is used for FLEX or derated thrust.
- CLB. Max climb thrust. If autothrust is active, this detent is used for climb (after thrust reduction), cruise, descent and approach.
- Idle. When the plane tells you to retard, this is the detent it wants. The reversers can only be pulled with the thrust levers in idle.


As explained above, directional control on a contaminated runway is the critical factor. If you're on all engines, it's all good since thrust is symmetrical. If you lose an engine, however, the derate gives a lower VMC, enabling you to climb out safely.

Operationally, if you use FLEX (assumed temperature) you may go to TOGA at any time since there is a margin to VMC. If you use Derate, you may not go to TOGA because the extra thrust on one engine could exceed the directional control ability of the aircraft.

Thanks for the info on the detents. I haven't been in the jumpseat of an Airbus since before September 2001. Always interested in learning more about those airplanes too.

How do you manually control thrust on an Airbus? I assume you disconnect the Autothrust and move the thrust levers like you would on a Boeing?

I didn't realize that directional control was the critical factor on a contaminated runway. I always assumed the critical factor was RTO braking capability.

As I mentioned earlier, Boeing guidance is the same as you state. However, you can advance the thrust levers beyond a fixed derate "in an emergency if ground contact is imminent". This should be obvious.

BoeingGuy wrote:

Starlionblue wrote:

To clarify the Airbus thrust lever detents, there are four:
- TOGA.
- FLEX/MCT. Max Continuous Thrust. In the take-off phase, this detent is used for FLEX or derated thrust.
- CLB. Max climb thrust. If autothrust is active, this detent is used for climb (after thrust reduction), cruise, descent and approach.
- Idle. When the plane tells you to retard, this is the detent it wants. The reversers can only be pulled with the thrust levers in idle.


As explained above, directional control on a contaminated runway is the critical factor. If you're on all engines, it's all good since thrust is symmetrical. If you lose an engine, however, the derate gives a lower VMC, enabling you to climb out safely.

Operationally, if you use FLEX (assumed temperature) you may go to TOGA at any time since there is a margin to VMC. If you use Derate, you may not go to TOGA because the extra thrust on one engine could exceed the directional control ability of the aircraft.

Thanks for the info on the detents. I haven't been in the jumpseat of an Airbus since before September 2001. Always interested in learning more about those airplanes too.

How do you manually control thrust on an Airbus? I assume you disconnect the Autothrust and move the thrust levers like you would on a Boeing?

I didn't realize that directional control was the critical factor on a contaminated runway. I always assumed the critical factor was RTO braking capability.

As I mentioned earlier, Boeing guidance is the same as you state. However, you can advance the thrust levers beyond a fixed derate "in an emergency if ground contact is imminent". This should be obvious.

As in your Boeing example, you would definitely move the thrust up in some situations. For example windshear, ground contact imminent, etc... On the 350, TOGA is permitted above F speed.

To disengage autothrust, the procedure is to move "ball to bat", meaning move the thrust lever, indicated by a "ball" on the instruments, to the current thrust level, indicated by a line, known as the "bat". The press the disconnect button on the side of the thrust lever. (You could just disengage the autothrust "as is" but since you're probably in the CLB detent FADEC would promptly give you max climb thrust...)

With autothrust off, the pilot controls thrust manually by moving the thrust levers from idle to TOGA. Thrust lever position tells FADEC the commanded thrust. Instruments tell the pilots commanded and actual thrust.

Breaking down normal ops in phases (unless the PF elects to use manual thrust).
- Taxi out. Thrust levers moved manually from idle toabove idle as needed.
- Take-off. Thrust levers set in either FLX/MCT or TOGA. Autothrust is armed.
- Climb. At the thrust reduction altitude, thrust levers retarded to CLB. Autothrust activates.
- Cruise. Thrust levers remain in CLB.
- Descent. Thrust levers remain in CLB.
- Approach. Thrust levers remain in CLB. In the flare, thrust levers are retarded to Idle. Autothrust disengages.
- Taxi in. Thrust levers moved manually from idle to above idle as needed.

Starlionblue wrote:

BoeingGuy wrote:

Starlionblue wrote:

To clarify the Airbus thrust lever detents, there are four:
- TOGA.
- FLEX/MCT. Max Continuous Thrust. In the take-off phase, this detent is used for FLEX or derated thrust.
- CLB. Max climb thrust. If autothrust is active, this detent is used for climb (after thrust reduction), cruise, descent and approach.
- Idle. When the plane tells you to retard, this is the detent it wants. The reversers can only be pulled with the thrust levers in idle.


As explained above, directional control on a contaminated runway is the critical factor. If you're on all engines, it's all good since thrust is symmetrical. If you lose an engine, however, the derate gives a lower VMC, enabling you to climb out safely.

Operationally, if you use FLEX (assumed temperature) you may go to TOGA at any time since there is a margin to VMC. If you use Derate, you may not go to TOGA because the extra thrust on one engine could exceed the directional control ability of the aircraft.

Thanks for the info on the detents. I haven't been in the jumpseat of an Airbus since before September 2001. Always interested in learning more about those airplanes too.

How do you manually control thrust on an Airbus? I assume you disconnect the Autothrust and move the thrust levers like you would on a Boeing?

I didn't realize that directional control was the critical factor on a contaminated runway. I always assumed the critical factor was RTO braking capability.

As I mentioned earlier, Boeing guidance is the same as you state. However, you can advance the thrust levers beyond a fixed derate "in an emergency if ground contact is imminent". This should be obvious.

As in your Boeing example, you would definitely move the thrust up in some situations. For example windshear, ground contact imminent, etc... On the 350, TOGA is permitted above F speed.

To disengage autothrust, the procedure is to move "ball to bat", meaning move the thrust lever, indicated by a "ball" on the instruments, to the current thrust level, indicated by a line, known as the "bat". The press the disconnect button on the side of the thrust lever. (You could just disengage the autothrust "as is" but since you're probably in the CLB detent FADEC would promptly give you max climb thrust...)

With autothrust off, the pilot controls thrust manually by moving the thrust levers from idle to TOGA. Thrust lever position tells FADEC the commanded thrust. Instruments tell the pilots commanded and actual thrust.

Breaking down normal ops in phases (unless the PF elects to use manual thrust).
- Taxi out. Thrust levers moved manually from idle toabove idle as needed.
- Take-off. Thrust levers set in either FLX/MCT or TOGA. Autothrust is armed.
- Climb. At the thrust reduction altitude, thrust levers retarded to CLB. Autothrust activates.
- Cruise. Thrust levers remain in CLB.
- Descent. Thrust levers remain in CLB.
- Approach. Thrust levers remain in CLB. In the flare, thrust levers are retarded to Idle. Autothrust disengages.
- Taxi in. Thrust levers moved manually from idle to above idle as needed.

Thanks. That is very informative.

This is where I like Boeing's design better (not that I'm biased or anything). You don't have to put the bat on the ball before taking over manual thrust control. It will already be there. The backdriven thrust levers are obviously always going to be in sync with the current commanded thrust.

The Boeing design is simple. There is a servo motor(s) that moves the thrust levers to the thrust setting that the Autothrottle is commanding. FADEC doesn't know whether the thrust levels were moved by the pilot's hand or the Autothrottle servo motor. It just sets the commanded thrust.

You don't have to move the thrust levers to different detents when the Autothrottle is engaged. For example, they move automatically from takeoff to climb thrust; they move automatically to idle during flare.

I’ve not flown an aircraft with fixed derates, a question comes to mind



Airbus and / or Boeing


If you firewall the throttles (thrust levers to the stops) will all derates be removed so the engines can deliver their maximum capable rated thrust ?

Max Q wrote:

I’ve not flown an aircraft with fixed derates, a question comes to mind



Airbus and / or Boeing


If you firewall the throttles (thrust levers to the stops) will all derates be removed so the engines can deliver their maximum capable rated thrust ?

That's an easy answer on a Boeing airplane. Yes.

Boeing airplanes will respond to any crew input. Say you select a "TO 1" 10% fixed derate. When you push TO/GA the Autothrottle will advance the Thrust Levers to a position corresponding to the 10% derate thrust. If you push the thrust levers to the forward stops, the engines will deliver their maximum capable rated thrust. Thus, you can manually remove the derate at any time.

(Prior to 80 knots you'd have to disconnect the Autothrottle or it would bring the thrust levers back to the derate position if you let go; after 80 knots the Autothrottle is in the HOLD mode and it will leave them where you put them).

Once the airplane is airborne you can also do this automatically. If you push the TO/GA Switch again, it will automatically remove the derate and move the thrust levels for the maximum rated takeoff thrust. If you've already transitioned to Climb Thrust then the autothrottle would advance to full rated Go-Around thrust.

BoeingGuy wrote:

You don't have to put the bat on the ball before taking over manual thrust control. It will already be there. The backdriven thrust levers are obviously always going to be in sync with the current commanded thrust.

That isn’t quiet true if the bus design, any time you want more thrust just advance them, you don’t have to match the thrust levers with the actual thrust, that is what I would do when coming in to land, I disengage the autothust and move them manually.

Max Q wrote:

If you firewall the throttles (thrust levers to the stops) will all derates be removed so the engines can deliver their maximum capable rated thrust ?

Advancing to TOGA gives you TOGA regardless what is programmed into the FM. Same as the Boeing don’t do it unless you are going to crash as Vmxa is lower with the derate.

zeke wrote:

Max Q wrote:

If you firewall the throttles (thrust levers to the stops) will all derates be removed so the engines can deliver their maximum capable rated thrust ?

Advancing to TOGA gives you TOGA regardless what is programmed into the FM. Same as the Boeing don’t do it unless you are going to crash as Vmxa is lower with the derate.

That’s assuming an engine is failed, correct? No harm in exceeding the derate thrust if both engines are running, right?

zeke wrote:

BoeingGuy wrote:

You don't have to put the bat on the ball before taking over manual thrust control. It will already be there. The backdriven thrust levers are obviously always going to be in sync with the current commanded thrust.

That isn’t quiet true if the bus design, any time you want more thrust just advance them, you don’t have to match the thrust levers with the actual thrust, that is what I would do when coming in to land, I disengage the autothust and move them manually.

I was in the jumpseat of an SN A330 for landing at BRU pre-9/11. Even though I know most carriers want automation on, the Captain disconnected the Autopilot and Autothrust at something like 10,000 feet. He just followed the Fligh Director as we were getting vectored around. He said he does this to keep his skills up. Good on him.

BoeingGuy wrote:

That’s assuming an engine is failed, correct? No harm in exceeding the derate thrust if both engines are running, right?

If you can tell me when an engine will fail in advance we can move to single engine airliners.

I hand fly most approaches, only when it’s not sensible I’ll leave it to the automation.

BoeingGuy wrote:

Max Q wrote:

I’ve not flown an aircraft with fixed derates, a question comes to mind



Airbus and / or Boeing


If you firewall the throttles (thrust levers to the stops) will all derates be removed so the engines can deliver their maximum capable rated thrust ?

That's an easy answer on a Boeing airplane. Yes.

Boeing airplanes will respond to any crew input. Say you select a "TO 1" 10% fixed derate. When you push TO/GA the Autothrottle will advance the Thrust Levers to a position corresponding to the 10% derate thrust. If you push the thrust levers to the forward stops, the engines will deliver their maximum capable rated thrust. Thus, you can manually remove the derate at any time.

(Prior to 80 knots you'd have to disconnect the Autothrottle or it would bring the thrust levers back to the derate position if you let go; after 80 knots the Autothrottle is in the HOLD mode and it will leave them where you put them).

Once the airplane is airborne you can also do this automatically. If you push the TO/GA Switch again, it will automatically remove the derate and move the thrust levels for the maximum rated takeoff thrust. If you've already transitioned to Climb Thrust then the autothrottle would advance to full rated Go-Around thrust.

Thanks for that and that’s understood



When I referred to fixed derates I really meant those derates not adjustable by the pilots



Certain engines have pin selectable max thrust levels so to refine my question further


When operating an engine that has been limited in such a manner will moving the throttles to the stops remove this limit
and allow it to produce maximum rated thrust at the highest pin selectable level ?


I suspect not

Max, I think you are right. The pin selector is a physical change to the control unit of an otherwise identical engine- a chip in the engine control that determines allowable thrust (I envisage it like the fuel mapping eeprom on a “chipped” car to increase performance - same engine but different fueling map). The unit tells the FADEC how much thrust the engine has, effectively re-scaling the arc of the thrust levers. So even if the engine is physically capable of Say 27k, if it’s pinned at 24k with a 10% derate selected, firewalling the levers will override the selected derate but still only give a max of 24k at manual TOGA

BoeingGuy wrote:

Starlionblue wrote:

BoeingGuy wrote:

Thanks for the info on the detents. I haven't been in the jumpseat of an Airbus since before September 2001. Always interested in learning more about those airplanes too.

How do you manually control thrust on an Airbus? I assume you disconnect the Autothrust and move the thrust levers like you would on a Boeing?

I didn't realize that directional control was the critical factor on a contaminated runway. I always assumed the critical factor was RTO braking capability.

As I mentioned earlier, Boeing guidance is the same as you state. However, you can advance the thrust levers beyond a fixed derate "in an emergency if ground contact is imminent". This should be obvious.

As in your Boeing example, you would definitely move the thrust up in some situations. For example windshear, ground contact imminent, etc... On the 350, TOGA is permitted above F speed.

To disengage autothrust, the procedure is to move "ball to bat", meaning move the thrust lever, indicated by a "ball" on the instruments, to the current thrust level, indicated by a line, known as the "bat". The press the disconnect button on the side of the thrust lever. (You could just disengage the autothrust "as is" but since you're probably in the CLB detent FADEC would promptly give you max climb thrust...)

With autothrust off, the pilot controls thrust manually by moving the thrust levers from idle to TOGA. Thrust lever position tells FADEC the commanded thrust. Instruments tell the pilots commanded and actual thrust.

Breaking down normal ops in phases (unless the PF elects to use manual thrust).
- Taxi out. Thrust levers moved manually from idle toabove idle as needed.
- Take-off. Thrust levers set in either FLX/MCT or TOGA. Autothrust is armed.
- Climb. At the thrust reduction altitude, thrust levers retarded to CLB. Autothrust activates.
- Cruise. Thrust levers remain in CLB.
- Descent. Thrust levers remain in CLB.
- Approach. Thrust levers remain in CLB. In the flare, thrust levers are retarded to Idle. Autothrust disengages.
- Taxi in. Thrust levers moved manually from idle to above idle as needed.

Thanks. That is very informative.

This is where I like Boeing's design better (not that I'm biased or anything). You don't have to put the bat on the ball before taking over manual thrust control. It will already be there. The backdriven thrust levers are obviously always going to be in sync with the current commanded thrust.

The Boeing design is simple. There is a servo motor(s) that moves the thrust levers to the thrust setting that the Autothrottle is commanding. FADEC doesn't know whether the thrust levels were moved by the pilot's hand or the Autothrottle servo motor. It just sets the commanded thrust.

You don't have to move the thrust levers to different detents when the Autothrottle is engaged. For example, they move automatically from takeoff to climb thrust; they move automatically to idle during flare.

I would argue that the Airbus design is simpler, since you're doing away with the servos. Both designs have their advantages and disadvantages.

What do you do on Boeing if you want to delay thrust reduction after take-off, or delay idle in the flare?

Another thing, and correct me if I'm wrong. In a Boeing if you push the levers forward to TOGA, the autothrottle can retard them from there, right? Thinking of last year's Emirates 777 accident in DXB. On Airbus if you push the thrust levers to TOGA the automation can't retard the thrust.

Again, correct me if I'm wrong: In an Airbus, if you got to TOGA during the approach, thrust will increase to TOGA and go-around phase will be activated, with associated mode changes, waking up of flight directors, etc... One instinctive movement for everything. AFAIK on a Boeing you have to both advance the thrust levers and press the TOGA buttons, or the modes won't change.

Starlionblue wrote:

BoeingGuy wrote:

Starlionblue wrote:

As in your Boeing example, you would definitely move the thrust up in some situations. For example windshear, ground contact imminent, etc... On the 350, TOGA is permitted above F speed.

To disengage autothrust, the procedure is to move "ball to bat", meaning move the thrust lever, indicated by a "ball" on the instruments, to the current thrust level, indicated by a line, known as the "bat". The press the disconnect button on the side of the thrust lever. (You could just disengage the autothrust "as is" but since you're probably in the CLB detent FADEC would promptly give you max climb thrust...)

With autothrust off, the pilot controls thrust manually by moving the thrust levers from idle to TOGA. Thrust lever position tells FADEC the commanded thrust. Instruments tell the pilots commanded and actual thrust.

Breaking down normal ops in phases (unless the PF elects to use manual thrust).
- Taxi out. Thrust levers moved manually from idle toabove idle as needed.
- Take-off. Thrust levers set in either FLX/MCT or TOGA. Autothrust is armed.
- Climb. At the thrust reduction altitude, thrust levers retarded to CLB. Autothrust activates.
- Cruise. Thrust levers remain in CLB.
- Descent. Thrust levers remain in CLB.
- Approach. Thrust levers remain in CLB. In the flare, thrust levers are retarded to Idle. Autothrust disengages.
- Taxi in. Thrust levers moved manually from idle to above idle as needed.

Thanks. That is very informative.

This is where I like Boeing's design better (not that I'm biased or anything). You don't have to put the bat on the ball before taking over manual thrust control. It will already be there. The backdriven thrust levers are obviously always going to be in sync with the current commanded thrust.

The Boeing design is simple. There is a servo motor(s) that moves the thrust levers to the thrust setting that the Autothrottle is commanding. FADEC doesn't know whether the thrust levels were moved by the pilot's hand or the Autothrottle servo motor. It just sets the commanded thrust.

You don't have to move the thrust levers to different detents when the Autothrottle is engaged. For example, they move automatically from takeoff to climb thrust; they move automatically to idle during flare.

I would argue that the Airbus design is simpler, since you're doing away with the servos. Both designs have their advantages and disadvantages.

What do you do on Boeing if you want to delay thrust reduction after take-off, or delay idle in the flare?

Another thing, and correct me if I'm wrong. In a Boeing if you push the levers forward to TOGA, the autothrottle can retard them from there, right? Thinking of last year's Emirates 777 accident in DXB. On Airbus if you push the thrust levers to TOGA the automation can't retard the thrust.

Again, correct me if I'm wrong: In an Airbus, if you got to TOGA during the approach, thrust will increase to TOGA and go-around phase will be activated, with associated mode changes, waking up of flight directors, etc... One instinctive movement for everything. AFAIK on a Boeing you have to both advance the thrust levers and press the TOGA buttons, or the modes won't change.

In a Boeing, if you want to delay thrust reduction after take off you simply select
that later, either by programming a higher
thrust reduction altitude or selecting VNAV / FLCH when you choose to, as usual if in doubt you can disconnect AT and set it manually


If you want to delay idle on the flare, AT on you can easily override them, disconnect AT and / or set thrust manually



In a Boeing you don’t push the throttles forward to TOGA, you push the TOGA switch once and the throttles advance to give you a 2000 fpm climb, push twice to select TOGA thrust, manually pushing up the power should not be necessary


However, if is an aircraft like any other, if it’s not doing what you want it to do disconnect and FLY the damn thing


There’s no excuse for sitting back, trusting the automation and hoping for the best, that’s ridiculous and a total abrogation of your responsibility as a pilot


And thats what happened with Asiana in SFO, Emirates in DXB and Turkish in AMS to name a few


Those pilots became passengers, sat back and let their perfectly functional aircraft crash

Max Q wrote:

Starlionblue wrote:

BoeingGuy wrote:

Thanks. That is very informative.

This is where I like Boeing's design better (not that I'm biased or anything). You don't have to put the bat on the ball before taking over manual thrust control. It will already be there. The backdriven thrust levers are obviously always going to be in sync with the current commanded thrust.

The Boeing design is simple. There is a servo motor(s) that moves the thrust levers to the thrust setting that the Autothrottle is commanding. FADEC doesn't know whether the thrust levels were moved by the pilot's hand or the Autothrottle servo motor. It just sets the commanded thrust.

You don't have to move the thrust levers to different detents when the Autothrottle is engaged. For example, they move automatically from takeoff to climb thrust; they move automatically to idle during flare.

I would argue that the Airbus design is simpler, since you're doing away with the servos. Both designs have their advantages and disadvantages.

What do you do on Boeing if you want to delay thrust reduction after take-off, or delay idle in the flare?

Another thing, and correct me if I'm wrong. In a Boeing if you push the levers forward to TOGA, the autothrottle can retard them from there, right? Thinking of last year's Emirates 777 accident in DXB. On Airbus if you push the thrust levers to TOGA the automation can't retard the thrust.

Again, correct me if I'm wrong: In an Airbus, if you got to TOGA during the approach, thrust will increase to TOGA and go-around phase will be activated, with associated mode changes, waking up of flight directors, etc... One instinctive movement for everything. AFAIK on a Boeing you have to both advance the thrust levers and press the TOGA buttons, or the modes won't change.

In a Boeing, if you want to delay thrust reduction after take off you simply select
that later, either by programming a higher
thrust reduction altitude or selecting VNAV / FLCH when you choose to, as usual if in doubt you can disconnect AT and set it manually

If you want to delay idle on the flare, AT on you can easily override them, disconnect AT and / or set thrust manually

In a Boeing you don’t push the throttles forward to TOGA, you push the TOGA switch once and the throttles advance to give you a 2000 fpm climb, push twice to select TOGA thrust, manually pushing up the power should not be necessary

However, if is an aircraft like any other, if it’s not doing what you want it to do disconnect and FLY the damn thing

There’s no excuse for sitting back, trusting the automation and hoping for the best, that’s ridiculous and a total abrogation of your responsibility as a pilot

And thats what happened with Asiana in SFO, Emirates in DXB and Turkish in AMS to name a few

Those pilots became passengers, sat back and let their perfectly functional aircraft crash

Thanks for the info. Interesting to learn about the "other side".

Airbus stresses the "fly the plane" philosophy in the FCTM.

In the very start of the FCTM, in the "Golden Rules for Pilots" section: "Fly! Navigate! Communicate!". The section includes the phrase "The flight crew must therefore always keep in mind the key message: Fly the Aircraft, Fly the Aircraft, Fly the Aircraft..."


In the AP/FD monitoring section:
The main concern for the flight crew should be:
- WHAT IS THE AIRCRAFT EXPECTED TO FLY NOW?
- WHAT IS THE AIRCRAFT EXPECTED TO FLY NEXT?

If the aircraft does not fly as expected:
- If in managed mode, select the desired target.**
- Or, disengage the autopilot, and fly the aircraft manually.

** Meaning go to a selected mode, e.g. from NAV to HDG, thus selecting the value instead of letting the FM "drive".

Holy thread drift, Batman...

Max Q wrote:

Starlionblue wrote:

BoeingGuy wrote:

Thanks. That is very informative.

This is where I like Boeing's design better (not that I'm biased or anything). You don't have to put the bat on the ball before taking over manual thrust control. It will already be there. The backdriven thrust levers are obviously always going to be in sync with the current commanded thrust.

The Boeing design is simple. There is a servo motor(s) that moves the thrust levers to the thrust setting that the Autothrottle is commanding. FADEC doesn't know whether the thrust levels were moved by the pilot's hand or the Autothrottle servo motor. It just sets the commanded thrust.

You don't have to move the thrust levers to different detents when the Autothrottle is engaged. For example, they move automatically from takeoff to climb thrust; they move automatically to idle during flare.

I would argue that the Airbus design is simpler, since you're doing away with the servos. Both designs have their advantages and disadvantages.

What do you do on Boeing if you want to delay thrust reduction after take-off, or delay idle in the flare?

Another thing, and correct me if I'm wrong. In a Boeing if you push the levers forward to TOGA, the autothrottle can retard them from there, right? Thinking of last year's Emirates 777 accident in DXB. On Airbus if you push the thrust levers to TOGA the automation can't retard the thrust.

Again, correct me if I'm wrong: In an Airbus, if you got to TOGA during the approach, thrust will increase to TOGA and go-around phase will be activated, with associated mode changes, waking up of flight directors, etc... One instinctive movement for everything. AFAIK on a Boeing you have to both advance the thrust levers and press the TOGA buttons, or the modes won't change.

In a Boeing, if you want to delay thrust reduction after take off you simply select
that later, either by programming a higher
thrust reduction altitude or selecting VNAV / FLCH when you choose to, as usual if in doubt you can disconnect AT and set it manually


If you want to delay idle on the flare, AT on you can easily override them, disconnect AT and / or set thrust manually



In a Boeing you don’t push the throttles forward to TOGA, you push the TOGA switch once and the throttles advance to give you a 2000 fpm climb, push twice to select TOGA thrust, manually pushing up the power should not be necessary


However, if is an aircraft like any other, if it’s not doing what you want it to do disconnect and FLY the damn thing


There’s no excuse for sitting back, trusting the automation and hoping for the best, that’s ridiculous and a total abrogation of your responsibility as a pilot


And thats what happened with Asiana in SFO, Emirates in DXB and Turkish in AMS to name a few


Those pilots became passengers, sat back and let their perfectly functional aircraft crash

Well said. Saved me a long reply. On some models the Thrust Reduction Altitude is set in the software so can’t be changed. However, that only matters if VNAV is engaged.

The 757/767 don’t have automatic climb thrust reduction. You have to do something to get climb thrust such as select VNAV or FLCH. They also don’t have the second TO/GA push for Go-Around. You would have to push the thrust levers up if you want more than ~2000 fpm climb.

Lost in the thread still is this question


Can a Pilot override a pin selectable fixed derate by moving the thrust levers to the stops, attaining maximum certified thrust for that engine ?

Max Q wrote:

Lost in the thread still is this question


Can a Pilot override a pin selectable fixed derate by moving the thrust levers to the stops, attaining maximum certified thrust for that engine ?

No on civil airliners that I know of.

Max Q wrote:

Lost in the thread still is this question


Can a Pilot override a pin selectable fixed derate by moving the thrust levers to the stops, attaining maximum certified thrust for that engine ?

No, that’s the permanent thrust rating of the engine until the program pin is changed. It was answered above.

I thought so, thanks for the replies