Gear reduction on large turbofans












2












$begingroup$


Do engines like the GE90 and Trent 1000 use transmissions (planetary gears?) for RPM reduction on the fans, or are they welded directly to the same shaft as the low pressure turbine?










share|improve this question









$endgroup$

















    2












    $begingroup$


    Do engines like the GE90 and Trent 1000 use transmissions (planetary gears?) for RPM reduction on the fans, or are they welded directly to the same shaft as the low pressure turbine?










    share|improve this question









    $endgroup$















      2












      2








      2





      $begingroup$


      Do engines like the GE90 and Trent 1000 use transmissions (planetary gears?) for RPM reduction on the fans, or are they welded directly to the same shaft as the low pressure turbine?










      share|improve this question









      $endgroup$




      Do engines like the GE90 and Trent 1000 use transmissions (planetary gears?) for RPM reduction on the fans, or are they welded directly to the same shaft as the low pressure turbine?







      turbofan gearbox






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked 2 hours ago









      birdusbirdus

      395413




      395413






















          2 Answers
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          4












          $begingroup$

          Those with gear reduction are called geared turbofans. You can check the Wikipedia article on any engine, see its classification and specifications, and also check the linked citations.



          The GE90 and Trent 1000 are not geared turbofans. Wikipedia lists only 5 geared turbofans, with the biggest (a recent engine; first run 2008) powering the A320neo family (narrow-body jetliner) and other regional jets.



          Note: the fan blades are not welded, rather connected/attached. You can watch a fan removal here (noisy video).






          share|improve this answer











          $endgroup$













          • $begingroup$
            When I used the term "welded," I was really talking more about how the hub is attached to the shaft, not the blades to the hub, and wasn't necessarily being serious anyway. I had read the Wikipedia article on the GE90 before. In the specs, it doesn't say anything about being a geared turbofan. I guess you're saying that if it doesn't explicitly say geared, then I should assume it's not. Lame. It should be explicit. For example, it should say "direct drive" or something like that (just my opinion). Thanks for your answer.
            $endgroup$
            – birdus
            2 hours ago






          • 1




            $begingroup$
            @birdus: Unless stated, turbofans are direct drive (the most common form). When something becomes an outlier, it is stated.
            $endgroup$
            – ymb1
            2 hours ago



















          1












          $begingroup$

          To add to what @ymb1 said, and to expand on your question about "welded", @birdus:



          The NTSB accident dockets for Southwest 1380 / NTSB# DCA18MA142, Southwest 3472 / NTSB# DCA16FA217, and American 383 / NTSB# DCA17FA021 all show some great internals about turbofan engines and (mostly) what happens when things fail.



          Specifically, Page 15 of the NTSB's Powerplant Group Chairman's Factual Report for SWA1380 has a nice description of the blades and how they attach. It's not 100% clear but reading carefully, it does describe how the blades are attached to the fan disk which is then "bolted to the booster by 24 bolts" (which it further clarifies that, at least on the CFM56, the LPC Low Pressure Compressor is sometimes referred to as the "booster")...



          That said, the CFM56 and GE90 do share a common characteristic: the LPC (Low Pressure Compressor - aka "N1") actually has compressor stages attached to the same shaft as the fan.



          The Trent 1000 is pretty different - the entire Trent series really evolved from the venerable Rolls Royce RB211 and ever since then the entire series has been a triple-spool turbofan engine (as opposed to the twin-spools utilized by every(?) other manufacturer.)



          So on a RB211/Trent XXXX, you have 3 independent spools and 3 gauges in the cockpit: N1, N2, and N3 - corresponding to the LP, IP, and HP shafts (low/intermediate/high). The whole idea of this being to decouple all of the core compressor stages from the fan rotor. If you look at the various compressor stage/turbine stage configurations, the notable difference with a Rolls Royce RB211/Trent is that the Fan has its own LP turbine.



          The Trent 1000 it has "Compressor: one-stage LP (fan), eight-stage IP, six-stage HP compressor" and "Single-stage HP turbine (13391 RPM), single-stage IP turbine (8937 RPM), six-stage LP turbine (2683 RPM)". So that means that there's a 6-stage turbine at the back that then spins the one-stage big fan at the front.



          The entire purpose of the three spools - even though it is far more complicated than having 2 - is to allow the fan at the front to rotate at a different speed than the engine core compressor sections. Doing so allows you to run the core faster/hotter without spinning the fan at the front too fast.



          The PW1100G from Pratt & Whitney is their answer to the problem of needing to turn the fan at the front at different speeds. Instead of using 3 spools to accomplish the task, they use a gearbox. This allows for different fan blade geometry and allows for a much quieter engine. (Speaking from personal experience, the PW1100G on the A220/CS series is seriously quiet.)



          Not to be left behind, Rolls Royce is developing the "UltraFan" which will apparently vary the pitch of the fan blades during flight.






          share|improve this answer








          New contributor




          Daniel Jewell is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
          Check out our Code of Conduct.






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            2 Answers
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            2 Answers
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            4












            $begingroup$

            Those with gear reduction are called geared turbofans. You can check the Wikipedia article on any engine, see its classification and specifications, and also check the linked citations.



            The GE90 and Trent 1000 are not geared turbofans. Wikipedia lists only 5 geared turbofans, with the biggest (a recent engine; first run 2008) powering the A320neo family (narrow-body jetliner) and other regional jets.



            Note: the fan blades are not welded, rather connected/attached. You can watch a fan removal here (noisy video).






            share|improve this answer











            $endgroup$













            • $begingroup$
              When I used the term "welded," I was really talking more about how the hub is attached to the shaft, not the blades to the hub, and wasn't necessarily being serious anyway. I had read the Wikipedia article on the GE90 before. In the specs, it doesn't say anything about being a geared turbofan. I guess you're saying that if it doesn't explicitly say geared, then I should assume it's not. Lame. It should be explicit. For example, it should say "direct drive" or something like that (just my opinion). Thanks for your answer.
              $endgroup$
              – birdus
              2 hours ago






            • 1




              $begingroup$
              @birdus: Unless stated, turbofans are direct drive (the most common form). When something becomes an outlier, it is stated.
              $endgroup$
              – ymb1
              2 hours ago
















            4












            $begingroup$

            Those with gear reduction are called geared turbofans. You can check the Wikipedia article on any engine, see its classification and specifications, and also check the linked citations.



            The GE90 and Trent 1000 are not geared turbofans. Wikipedia lists only 5 geared turbofans, with the biggest (a recent engine; first run 2008) powering the A320neo family (narrow-body jetliner) and other regional jets.



            Note: the fan blades are not welded, rather connected/attached. You can watch a fan removal here (noisy video).






            share|improve this answer











            $endgroup$













            • $begingroup$
              When I used the term "welded," I was really talking more about how the hub is attached to the shaft, not the blades to the hub, and wasn't necessarily being serious anyway. I had read the Wikipedia article on the GE90 before. In the specs, it doesn't say anything about being a geared turbofan. I guess you're saying that if it doesn't explicitly say geared, then I should assume it's not. Lame. It should be explicit. For example, it should say "direct drive" or something like that (just my opinion). Thanks for your answer.
              $endgroup$
              – birdus
              2 hours ago






            • 1




              $begingroup$
              @birdus: Unless stated, turbofans are direct drive (the most common form). When something becomes an outlier, it is stated.
              $endgroup$
              – ymb1
              2 hours ago














            4












            4








            4





            $begingroup$

            Those with gear reduction are called geared turbofans. You can check the Wikipedia article on any engine, see its classification and specifications, and also check the linked citations.



            The GE90 and Trent 1000 are not geared turbofans. Wikipedia lists only 5 geared turbofans, with the biggest (a recent engine; first run 2008) powering the A320neo family (narrow-body jetliner) and other regional jets.



            Note: the fan blades are not welded, rather connected/attached. You can watch a fan removal here (noisy video).






            share|improve this answer











            $endgroup$



            Those with gear reduction are called geared turbofans. You can check the Wikipedia article on any engine, see its classification and specifications, and also check the linked citations.



            The GE90 and Trent 1000 are not geared turbofans. Wikipedia lists only 5 geared turbofans, with the biggest (a recent engine; first run 2008) powering the A320neo family (narrow-body jetliner) and other regional jets.



            Note: the fan blades are not welded, rather connected/attached. You can watch a fan removal here (noisy video).







            share|improve this answer














            share|improve this answer



            share|improve this answer








            edited 2 hours ago

























            answered 2 hours ago









            ymb1ymb1

            66k6210350




            66k6210350












            • $begingroup$
              When I used the term "welded," I was really talking more about how the hub is attached to the shaft, not the blades to the hub, and wasn't necessarily being serious anyway. I had read the Wikipedia article on the GE90 before. In the specs, it doesn't say anything about being a geared turbofan. I guess you're saying that if it doesn't explicitly say geared, then I should assume it's not. Lame. It should be explicit. For example, it should say "direct drive" or something like that (just my opinion). Thanks for your answer.
              $endgroup$
              – birdus
              2 hours ago






            • 1




              $begingroup$
              @birdus: Unless stated, turbofans are direct drive (the most common form). When something becomes an outlier, it is stated.
              $endgroup$
              – ymb1
              2 hours ago


















            • $begingroup$
              When I used the term "welded," I was really talking more about how the hub is attached to the shaft, not the blades to the hub, and wasn't necessarily being serious anyway. I had read the Wikipedia article on the GE90 before. In the specs, it doesn't say anything about being a geared turbofan. I guess you're saying that if it doesn't explicitly say geared, then I should assume it's not. Lame. It should be explicit. For example, it should say "direct drive" or something like that (just my opinion). Thanks for your answer.
              $endgroup$
              – birdus
              2 hours ago






            • 1




              $begingroup$
              @birdus: Unless stated, turbofans are direct drive (the most common form). When something becomes an outlier, it is stated.
              $endgroup$
              – ymb1
              2 hours ago
















            $begingroup$
            When I used the term "welded," I was really talking more about how the hub is attached to the shaft, not the blades to the hub, and wasn't necessarily being serious anyway. I had read the Wikipedia article on the GE90 before. In the specs, it doesn't say anything about being a geared turbofan. I guess you're saying that if it doesn't explicitly say geared, then I should assume it's not. Lame. It should be explicit. For example, it should say "direct drive" or something like that (just my opinion). Thanks for your answer.
            $endgroup$
            – birdus
            2 hours ago




            $begingroup$
            When I used the term "welded," I was really talking more about how the hub is attached to the shaft, not the blades to the hub, and wasn't necessarily being serious anyway. I had read the Wikipedia article on the GE90 before. In the specs, it doesn't say anything about being a geared turbofan. I guess you're saying that if it doesn't explicitly say geared, then I should assume it's not. Lame. It should be explicit. For example, it should say "direct drive" or something like that (just my opinion). Thanks for your answer.
            $endgroup$
            – birdus
            2 hours ago




            1




            1




            $begingroup$
            @birdus: Unless stated, turbofans are direct drive (the most common form). When something becomes an outlier, it is stated.
            $endgroup$
            – ymb1
            2 hours ago




            $begingroup$
            @birdus: Unless stated, turbofans are direct drive (the most common form). When something becomes an outlier, it is stated.
            $endgroup$
            – ymb1
            2 hours ago











            1












            $begingroup$

            To add to what @ymb1 said, and to expand on your question about "welded", @birdus:



            The NTSB accident dockets for Southwest 1380 / NTSB# DCA18MA142, Southwest 3472 / NTSB# DCA16FA217, and American 383 / NTSB# DCA17FA021 all show some great internals about turbofan engines and (mostly) what happens when things fail.



            Specifically, Page 15 of the NTSB's Powerplant Group Chairman's Factual Report for SWA1380 has a nice description of the blades and how they attach. It's not 100% clear but reading carefully, it does describe how the blades are attached to the fan disk which is then "bolted to the booster by 24 bolts" (which it further clarifies that, at least on the CFM56, the LPC Low Pressure Compressor is sometimes referred to as the "booster")...



            That said, the CFM56 and GE90 do share a common characteristic: the LPC (Low Pressure Compressor - aka "N1") actually has compressor stages attached to the same shaft as the fan.



            The Trent 1000 is pretty different - the entire Trent series really evolved from the venerable Rolls Royce RB211 and ever since then the entire series has been a triple-spool turbofan engine (as opposed to the twin-spools utilized by every(?) other manufacturer.)



            So on a RB211/Trent XXXX, you have 3 independent spools and 3 gauges in the cockpit: N1, N2, and N3 - corresponding to the LP, IP, and HP shafts (low/intermediate/high). The whole idea of this being to decouple all of the core compressor stages from the fan rotor. If you look at the various compressor stage/turbine stage configurations, the notable difference with a Rolls Royce RB211/Trent is that the Fan has its own LP turbine.



            The Trent 1000 it has "Compressor: one-stage LP (fan), eight-stage IP, six-stage HP compressor" and "Single-stage HP turbine (13391 RPM), single-stage IP turbine (8937 RPM), six-stage LP turbine (2683 RPM)". So that means that there's a 6-stage turbine at the back that then spins the one-stage big fan at the front.



            The entire purpose of the three spools - even though it is far more complicated than having 2 - is to allow the fan at the front to rotate at a different speed than the engine core compressor sections. Doing so allows you to run the core faster/hotter without spinning the fan at the front too fast.



            The PW1100G from Pratt & Whitney is their answer to the problem of needing to turn the fan at the front at different speeds. Instead of using 3 spools to accomplish the task, they use a gearbox. This allows for different fan blade geometry and allows for a much quieter engine. (Speaking from personal experience, the PW1100G on the A220/CS series is seriously quiet.)



            Not to be left behind, Rolls Royce is developing the "UltraFan" which will apparently vary the pitch of the fan blades during flight.






            share|improve this answer








            New contributor




            Daniel Jewell is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
            Check out our Code of Conduct.






            $endgroup$


















              1












              $begingroup$

              To add to what @ymb1 said, and to expand on your question about "welded", @birdus:



              The NTSB accident dockets for Southwest 1380 / NTSB# DCA18MA142, Southwest 3472 / NTSB# DCA16FA217, and American 383 / NTSB# DCA17FA021 all show some great internals about turbofan engines and (mostly) what happens when things fail.



              Specifically, Page 15 of the NTSB's Powerplant Group Chairman's Factual Report for SWA1380 has a nice description of the blades and how they attach. It's not 100% clear but reading carefully, it does describe how the blades are attached to the fan disk which is then "bolted to the booster by 24 bolts" (which it further clarifies that, at least on the CFM56, the LPC Low Pressure Compressor is sometimes referred to as the "booster")...



              That said, the CFM56 and GE90 do share a common characteristic: the LPC (Low Pressure Compressor - aka "N1") actually has compressor stages attached to the same shaft as the fan.



              The Trent 1000 is pretty different - the entire Trent series really evolved from the venerable Rolls Royce RB211 and ever since then the entire series has been a triple-spool turbofan engine (as opposed to the twin-spools utilized by every(?) other manufacturer.)



              So on a RB211/Trent XXXX, you have 3 independent spools and 3 gauges in the cockpit: N1, N2, and N3 - corresponding to the LP, IP, and HP shafts (low/intermediate/high). The whole idea of this being to decouple all of the core compressor stages from the fan rotor. If you look at the various compressor stage/turbine stage configurations, the notable difference with a Rolls Royce RB211/Trent is that the Fan has its own LP turbine.



              The Trent 1000 it has "Compressor: one-stage LP (fan), eight-stage IP, six-stage HP compressor" and "Single-stage HP turbine (13391 RPM), single-stage IP turbine (8937 RPM), six-stage LP turbine (2683 RPM)". So that means that there's a 6-stage turbine at the back that then spins the one-stage big fan at the front.



              The entire purpose of the three spools - even though it is far more complicated than having 2 - is to allow the fan at the front to rotate at a different speed than the engine core compressor sections. Doing so allows you to run the core faster/hotter without spinning the fan at the front too fast.



              The PW1100G from Pratt & Whitney is their answer to the problem of needing to turn the fan at the front at different speeds. Instead of using 3 spools to accomplish the task, they use a gearbox. This allows for different fan blade geometry and allows for a much quieter engine. (Speaking from personal experience, the PW1100G on the A220/CS series is seriously quiet.)



              Not to be left behind, Rolls Royce is developing the "UltraFan" which will apparently vary the pitch of the fan blades during flight.






              share|improve this answer








              New contributor




              Daniel Jewell is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
              Check out our Code of Conduct.






              $endgroup$
















                1












                1








                1





                $begingroup$

                To add to what @ymb1 said, and to expand on your question about "welded", @birdus:



                The NTSB accident dockets for Southwest 1380 / NTSB# DCA18MA142, Southwest 3472 / NTSB# DCA16FA217, and American 383 / NTSB# DCA17FA021 all show some great internals about turbofan engines and (mostly) what happens when things fail.



                Specifically, Page 15 of the NTSB's Powerplant Group Chairman's Factual Report for SWA1380 has a nice description of the blades and how they attach. It's not 100% clear but reading carefully, it does describe how the blades are attached to the fan disk which is then "bolted to the booster by 24 bolts" (which it further clarifies that, at least on the CFM56, the LPC Low Pressure Compressor is sometimes referred to as the "booster")...



                That said, the CFM56 and GE90 do share a common characteristic: the LPC (Low Pressure Compressor - aka "N1") actually has compressor stages attached to the same shaft as the fan.



                The Trent 1000 is pretty different - the entire Trent series really evolved from the venerable Rolls Royce RB211 and ever since then the entire series has been a triple-spool turbofan engine (as opposed to the twin-spools utilized by every(?) other manufacturer.)



                So on a RB211/Trent XXXX, you have 3 independent spools and 3 gauges in the cockpit: N1, N2, and N3 - corresponding to the LP, IP, and HP shafts (low/intermediate/high). The whole idea of this being to decouple all of the core compressor stages from the fan rotor. If you look at the various compressor stage/turbine stage configurations, the notable difference with a Rolls Royce RB211/Trent is that the Fan has its own LP turbine.



                The Trent 1000 it has "Compressor: one-stage LP (fan), eight-stage IP, six-stage HP compressor" and "Single-stage HP turbine (13391 RPM), single-stage IP turbine (8937 RPM), six-stage LP turbine (2683 RPM)". So that means that there's a 6-stage turbine at the back that then spins the one-stage big fan at the front.



                The entire purpose of the three spools - even though it is far more complicated than having 2 - is to allow the fan at the front to rotate at a different speed than the engine core compressor sections. Doing so allows you to run the core faster/hotter without spinning the fan at the front too fast.



                The PW1100G from Pratt & Whitney is their answer to the problem of needing to turn the fan at the front at different speeds. Instead of using 3 spools to accomplish the task, they use a gearbox. This allows for different fan blade geometry and allows for a much quieter engine. (Speaking from personal experience, the PW1100G on the A220/CS series is seriously quiet.)



                Not to be left behind, Rolls Royce is developing the "UltraFan" which will apparently vary the pitch of the fan blades during flight.






                share|improve this answer








                New contributor




                Daniel Jewell is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                Check out our Code of Conduct.






                $endgroup$



                To add to what @ymb1 said, and to expand on your question about "welded", @birdus:



                The NTSB accident dockets for Southwest 1380 / NTSB# DCA18MA142, Southwest 3472 / NTSB# DCA16FA217, and American 383 / NTSB# DCA17FA021 all show some great internals about turbofan engines and (mostly) what happens when things fail.



                Specifically, Page 15 of the NTSB's Powerplant Group Chairman's Factual Report for SWA1380 has a nice description of the blades and how they attach. It's not 100% clear but reading carefully, it does describe how the blades are attached to the fan disk which is then "bolted to the booster by 24 bolts" (which it further clarifies that, at least on the CFM56, the LPC Low Pressure Compressor is sometimes referred to as the "booster")...



                That said, the CFM56 and GE90 do share a common characteristic: the LPC (Low Pressure Compressor - aka "N1") actually has compressor stages attached to the same shaft as the fan.



                The Trent 1000 is pretty different - the entire Trent series really evolved from the venerable Rolls Royce RB211 and ever since then the entire series has been a triple-spool turbofan engine (as opposed to the twin-spools utilized by every(?) other manufacturer.)



                So on a RB211/Trent XXXX, you have 3 independent spools and 3 gauges in the cockpit: N1, N2, and N3 - corresponding to the LP, IP, and HP shafts (low/intermediate/high). The whole idea of this being to decouple all of the core compressor stages from the fan rotor. If you look at the various compressor stage/turbine stage configurations, the notable difference with a Rolls Royce RB211/Trent is that the Fan has its own LP turbine.



                The Trent 1000 it has "Compressor: one-stage LP (fan), eight-stage IP, six-stage HP compressor" and "Single-stage HP turbine (13391 RPM), single-stage IP turbine (8937 RPM), six-stage LP turbine (2683 RPM)". So that means that there's a 6-stage turbine at the back that then spins the one-stage big fan at the front.



                The entire purpose of the three spools - even though it is far more complicated than having 2 - is to allow the fan at the front to rotate at a different speed than the engine core compressor sections. Doing so allows you to run the core faster/hotter without spinning the fan at the front too fast.



                The PW1100G from Pratt & Whitney is their answer to the problem of needing to turn the fan at the front at different speeds. Instead of using 3 spools to accomplish the task, they use a gearbox. This allows for different fan blade geometry and allows for a much quieter engine. (Speaking from personal experience, the PW1100G on the A220/CS series is seriously quiet.)



                Not to be left behind, Rolls Royce is developing the "UltraFan" which will apparently vary the pitch of the fan blades during flight.







                share|improve this answer








                New contributor




                Daniel Jewell is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                Check out our Code of Conduct.









                share|improve this answer



                share|improve this answer






                New contributor




                Daniel Jewell is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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                answered 1 hour ago









                Daniel JewellDaniel Jewell

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                111




                New contributor




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                New contributor





                Daniel Jewell is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                Check out our Code of Conduct.






                Daniel Jewell is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
                Check out our Code of Conduct.






























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