Hey,can some one please explain me the two? i am not sure, i read about it but didn't entirely understand.reduction is when the flaps will retracted?and acceleration height is when the auto pilot will leave the v2+10 and begin to accelerate?thanks.

Reduction is when the autothrottle will decrease engine power to the necessary climb thrust.Acceleration is when the nose is to be lowered to allow the aircraft to accelerate. When the aircraft starts accelerating is when you raise the flaps.

Edited February 12, 201214 yr by Kenny

Reduction is when the autothrottle will decrease engine power to the necessary climb thrust.Acceleration is when the nose is to be lowered to allow the aircraft to accelerate. When the aircraft starts accelerating is when you raise the flaps.

thank you, but i don't get it why is the throttle decrease if the thrust for take off let's say 83.3% so will it decrease to a lower thrust?

thank you, but i don't get it why is the throttle decrease if the thrust for take off let's say 83.3% so will it decrease to a lower thrust?

I think it has more to do with thrust limits. The engines may be providing takeoff thrust at 83.3% N₁ but will be providing climb thrust at 83.3% N₁. I think someone can explain it better than I can.

Climb thrust is lower than takeoff thrust, yes.

Climb thrust is lower than takeoff thrust, yes.

not true according to the fact, let's take my previous flight, the take off thrust was 84.4% but after the acceleration at the climb thrust it increased to 90.0%.BTW the reduction has to be after the acceleration height, true? thanks again

not true according to the fact, let's take my previous flight, the take off thrust was 84.4% but after the acceleration at the climb thrust it increased to 90.0%.BTW the reduction has to be after the acceleration height, true? thanks again

You do not need the thrust needed to get the aircraft off the ground in order to climb. True the N1 value may increase but the thrust is less than takeoff thrust.According to one of the ICAO noise abatement procedures you takeoff with takeoff flaps at whatever pitch required to maintain V2 (V2+10) until you get to 3000 feet then reduce to climb and start retracting the flaps. So it depends on the specific takeoff. There are times that you can have the same acceleration and reduction height.

not true according to the fact, let's take my previous flight, the take off thrust was 84.4% but after the acceleration at the climb thrust it increased to 90.0%. Rarely, but sometimes happens.BTW the reduction has to be after the acceleration height, true? thanks again No, it does not and isn't normally.

Daniel,An example of thrust reduction and acceleration is found in a noise abatement climb, details here:www.b737mrg.net/downloads/b737mrg_noise.pdfMore specific variations for a particular airport can be found in the relevant AIP.

Edited February 12, 201214 yr by srcooke

True the N1 value may increase but the thrust is less than takeoff thrust.

This is not correct. If N1 increases at accel height, thrust is increasing. A cause for this may be using derated TO thrust but using full CLB (not CLB 1 or 2). On the N1 limit page during preflight, you set your TO thrust limit/derate and CLB derate. That page will show you TO N1 %. Then go to the CLB page and it will show the selected CLB N1 %. Normal procedures would dictate a higher TO %N1 than CLB. If your CLB %N1 is showing higher than TO, you need to select a higher CLB derate (less climb thrust, CLB1 or CLB2). Alternatively, you can reduce the TO derate (higher TO thrust). The goal is to have TO thrust higher % than climb thrust.Okay, well really the goal is to use only enough TO thrust to get safely airborne whilst also leaving enough runway to stop if something happens right at or before V1. Then of course also to reduce thrust (%N1) for climb to save on engine wear while maintaining adequate separation between the aircraft and any obstacles, following ATC, procedures, etc.So I guess it's possible to have higher CLB thrust than TO, but that would be a special circumstance, probably applying to <5% of the world's airports.

Edited February 12, 201214 yr by adamant365

You do not need the thrust needed to get the aircraft off the ground in order to climb. True the N1 value may increase but the thrust is less than takeoff thrust.According to one of the ICAO noise abatement procedures you takeoff with takeoff flaps at whatever pitch required to maintain V2 (V2+10) until you get to 3000 feet then reduce to climb and start retracting the flaps. So it depends on the specific takeoff. There are times that you can have the same acceleration and reduction height.

thank you

In general, It is possible to have a higher climb thrust than takeoff thrust. This all depends on the reduction made for takeoff. In FAA certified aircraft, you must have atleast 75% of the rated thrust for takeoff. When I was flying DC-10s, it was common to see the thrust remain the same or increase when selecting climb thrust at light weights. This would happen in the DC10 because we only derated the takeoff thrust. Climb thrust was all ways the max climb thrust based on conditions. Some aircraft also allows you to derate the climb thrust. Regardless of the thrust mode selected, you will get the same thrust at a given N1.Accel height standard is 1500ft above the airport(FAA). This could be lower or higher depending on your takeoff profile. The reduction usually takes place at this point. FAA certified aircraft has a limit of 5 minutes takeoff thrust all engines and 10 minutes engine out. Beyond that there is MCT(max continous thrust) or climb thrust depending on the aircraft. So in general, if you have an engine failure, you will level off at accel and clean up but keep in takeoff thrust for the extra 5 minutes. If you are all engine and need to continue the climb for obsticles etc, stay configured or clean up and select climb/MCT at accel height.

In general, It is possible to have a higher climb thrust than takeoff thrust. This all depends on the reduction made for takeoff. In FAA certified aircraft, you must have atleast 75% of the rated thrust for takeoff. When I was flying DC-10s, it was common to see the thrust remain the same or increase when selecting climb thrust at light weights. This would happen in the DC10 because we only derated the takeoff thrust. Climb thrust was all ways the max climb thrust based on conditions. Some aircraft also allows you to derate the climb thrust. Regardless of the thrust mode selected, you will get the same thrust at a given N1.Accel height standard is 1500ft above the airport(FAA). This could be lower or higher depending on your takeoff profile. The reduction usually takes place at this point. FAA certified aircraft has a limit of 5 minutes takeoff thrust all engines and 10 minutes engine out. Beyond that there is MCT(max continous thrust) or climb thrust depending on the aircraft. So in general, if you have an engine failure, you will level off at accel and clean up but keep in takeoff thrust for the extra 5 minutes. If you are all engine and need to continue the climb for obsticles etc, stay configured or clean up and select climb/MCT at accel height.

great, it's always nice to hear from you, thank you sir(: