What are takeoff thrust options on Boeing aircraft?
737
747
757/767
777
787
Can you list the possibilities and the differences?
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- skyhawkmatthew
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Re: Boeing Takeoff thrust options
What do you mean? Different maximum engine thrust ratings, or FMC takeoff performance options?
For the latter, on the 777, we have two methods of selecting a derate.
The first is a straight reduction of the rated thrust: we can select TO, TO-1 or TO-2, which are full thrust, minus 10% and minus 20% respectively.
Once that selection has been made, we can then (as long as we are not taking off on a contaminated runway) also apply an “assumed temperature” derate (known as “Flex” on an Airbus) by entering a temperature greater than ambient. This further reduces engine thrust by telling the EECs we want the engine to produce the amount of thrust we would expect if the outside temperature was actually that value.
On the -300ER in addition to TO, TO-1 and TO-2, we also have TO-B “bump” thrust which is only available in certain altitude and temperature conditions, and enables up to an extra 2.5% on top of maximum rated thrust for very performance-limited situations (e.g. JNB on a warm day). Obviously, no assumed temperature derate can be used with this mode as it would be pointless!
For the latter, on the 777, we have two methods of selecting a derate.
The first is a straight reduction of the rated thrust: we can select TO, TO-1 or TO-2, which are full thrust, minus 10% and minus 20% respectively.
Once that selection has been made, we can then (as long as we are not taking off on a contaminated runway) also apply an “assumed temperature” derate (known as “Flex” on an Airbus) by entering a temperature greater than ambient. This further reduces engine thrust by telling the EECs we want the engine to produce the amount of thrust we would expect if the outside temperature was actually that value.
On the -300ER in addition to TO, TO-1 and TO-2, we also have TO-B “bump” thrust which is only available in certain altitude and temperature conditions, and enables up to an extra 2.5% on top of maximum rated thrust for very performance-limited situations (e.g. JNB on a warm day). Obviously, no assumed temperature derate can be used with this mode as it would be pointless!
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- GalaxyFlyer
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Re: Boeing Takeoff thrust options
Using "reduced" or "FLEX" thrust is NOT a derate. A derate is very different from reduced thrust calculations. Reduced thrust performance is all predicated on full thrust being available, so speeds like Vmcg and Vmca use full rated thrust. A derate is like a different engine was installed; all performance numbers, especially the "lines in the sand" like Vmcg use the derate thrust.
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- skyhawkmatthew
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Re: Boeing Takeoff thrust options
Apologies, I should wake up fully before posting. Substitute "thrust reduction" for "derate." And yes, as you say the performance speeds are based on rated thrust so if necessary the thrust levers can be firewalled or the reduction cancelled without causing a Vmcg/Vmca excursion.
Re: Boeing Takeoff thrust options
Too many to list.
Just to name one plane I'm quite familiar with:
B737 classics.
At least two engine options, CFM56-3B or 3C. 3C were rated on four different thrusts (18.5, 20, 22 and 23.5k lbs). 3B probably similar, however ratings could be a bit different, especially when comparing climb/cruise thrust. Almost any combination could be used (some ewxceptions like there was no 23.5k option on 500, or 18.5k on 400, and 300 as well IIRC).
So, only classics would give like 20 different engines and options? NG would be even longer. Whole list you requested would go over 100 positions. And all the data necessary is already on the net.
My best advise is - go ahead and compile your list. Maybe someone compiled the list you requested, but I think it would be quicker to go and do the research yourself.
Cheers,
Adam
Just to name one plane I'm quite familiar with:
B737 classics.
At least two engine options, CFM56-3B or 3C. 3C were rated on four different thrusts (18.5, 20, 22 and 23.5k lbs). 3B probably similar, however ratings could be a bit different, especially when comparing climb/cruise thrust. Almost any combination could be used (some ewxceptions like there was no 23.5k option on 500, or 18.5k on 400, and 300 as well IIRC).
So, only classics would give like 20 different engines and options? NG would be even longer. Whole list you requested would go over 100 positions. And all the data necessary is already on the net.
My best advise is - go ahead and compile your list. Maybe someone compiled the list you requested, but I think it would be quicker to go and do the research yourself.
Cheers,
Adam
Re: Boeing Takeoff thrust options
Fixed Derates and Assumed Temperature Derates are baseline on the 747, 777, and 787.
For the 767, Assumed Temperature Derates are baseline. Fixed derates are optional.
For the 767, Assumed Temperature Derates are baseline. Fixed derates are optional.
Re: Boeing Takeoff thrust options
skyhawkmatthew wrote:Apologies, I should wake up fully before posting. Substitute "thrust reduction" for "derate." And yes, as you say the performance speeds are based on rated thrust so if necessary the thrust levers can be firewalled or the reduction cancelled without causing a Vmcg/Vmca excursion.
For fixed derates, the guidance is you can only increase thrust beyond the derate if ground contact is imminent.
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