Why complex landing gears are used instead of simple,reliability and light weight muscle wire or shape memory...

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Why complex landing gears are used instead of simple,reliability and light weight muscle wire or shape memory alloys?



Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 23, 2019 at 23:30 UTC (7:30pm US/Eastern)Why safe take off weight exceeds the safe landing weight?Why does the Harrier jet have four landing gears?Is there a good reason why modern airliners can't have conventional landing gears (vs. tricycle landing gears)?Is it feasible to replace brakes on airplanes with electric motor/generator?Why are there so many moving parts used in the landing gear?Why do some A320s have double bogey landing gears?Why are aircraft tires not pre-spun prior to landing?Why do landing gears smoke upon impact?Why was the cabin light turned off before landing?Why don't nose landing gears have brakes?












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Muscle wires actuators are really simple, high power density and reliable. Landing gears on other hand are used only twice per flight while taking off and landing (if everything goes well though). During flight these machines are not useful and there are number of gear up landing because of landing gear failure.



What is so complex in landing gear?



Why electric motors/ hydraulic actuators are used instead of muscle wire actuators in landing gear which are simple, light weight, reliable and cheap?
(If it is electric power requirements, that can be achieved by supercapacitors.)










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  • $begingroup$
    You may provide some links or reading about muscle wire actuator as I'm not sure how familiar is the aviation.SE community with this kind of actuator and how it is operated. Moreover, you may restrict your question to one kind of aircraft as many GA aircrafts are equipped with fixed landing gear
    $endgroup$
    – Manu H
    4 hours ago


















1












$begingroup$


Muscle wires actuators are really simple, high power density and reliable. Landing gears on other hand are used only twice per flight while taking off and landing (if everything goes well though). During flight these machines are not useful and there are number of gear up landing because of landing gear failure.



What is so complex in landing gear?



Why electric motors/ hydraulic actuators are used instead of muscle wire actuators in landing gear which are simple, light weight, reliable and cheap?
(If it is electric power requirements, that can be achieved by supercapacitors.)










share|improve this question









New contributor




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







$endgroup$












  • $begingroup$
    You may provide some links or reading about muscle wire actuator as I'm not sure how familiar is the aviation.SE community with this kind of actuator and how it is operated. Moreover, you may restrict your question to one kind of aircraft as many GA aircrafts are equipped with fixed landing gear
    $endgroup$
    – Manu H
    4 hours ago
















1












1








1





$begingroup$


Muscle wires actuators are really simple, high power density and reliable. Landing gears on other hand are used only twice per flight while taking off and landing (if everything goes well though). During flight these machines are not useful and there are number of gear up landing because of landing gear failure.



What is so complex in landing gear?



Why electric motors/ hydraulic actuators are used instead of muscle wire actuators in landing gear which are simple, light weight, reliable and cheap?
(If it is electric power requirements, that can be achieved by supercapacitors.)










share|improve this question









New contributor




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







$endgroup$




Muscle wires actuators are really simple, high power density and reliable. Landing gears on other hand are used only twice per flight while taking off and landing (if everything goes well though). During flight these machines are not useful and there are number of gear up landing because of landing gear failure.



What is so complex in landing gear?



Why electric motors/ hydraulic actuators are used instead of muscle wire actuators in landing gear which are simple, light weight, reliable and cheap?
(If it is electric power requirements, that can be achieved by supercapacitors.)







aircraft-design landing landing-gear






share|improve this question









New contributor




SRD 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 question









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SRD 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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share|improve this question








edited 3 hours ago







SRD













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asked 4 hours ago









SRDSRD

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






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












  • $begingroup$
    You may provide some links or reading about muscle wire actuator as I'm not sure how familiar is the aviation.SE community with this kind of actuator and how it is operated. Moreover, you may restrict your question to one kind of aircraft as many GA aircrafts are equipped with fixed landing gear
    $endgroup$
    – Manu H
    4 hours ago




















  • $begingroup$
    You may provide some links or reading about muscle wire actuator as I'm not sure how familiar is the aviation.SE community with this kind of actuator and how it is operated. Moreover, you may restrict your question to one kind of aircraft as many GA aircrafts are equipped with fixed landing gear
    $endgroup$
    – Manu H
    4 hours ago


















$begingroup$
You may provide some links or reading about muscle wire actuator as I'm not sure how familiar is the aviation.SE community with this kind of actuator and how it is operated. Moreover, you may restrict your question to one kind of aircraft as many GA aircrafts are equipped with fixed landing gear
$endgroup$
– Manu H
4 hours ago






$begingroup$
You may provide some links or reading about muscle wire actuator as I'm not sure how familiar is the aviation.SE community with this kind of actuator and how it is operated. Moreover, you may restrict your question to one kind of aircraft as many GA aircrafts are equipped with fixed landing gear
$endgroup$
– Manu H
4 hours ago












1 Answer
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oldest

votes


















2












$begingroup$

Shape-memory alloys change their shape with temperature, with control usually achieved with electric heating in one direction, and back with convective heat transfer to the environment. There is one specific temperature where the change in shape occurs. There are two huge problems with this:





  1. The operating temperature range for gear actuators is huge. It may easily be below -40°C on a cold arctic night, but on a hot tropical day the sun can easily heat the structure to upward of +60°C. That means the transformation temperature must be pretty high, but that means a lot of energy has to be put to heating it, especially if the ambient temperature happens to be low on the day.



    Note that the actuators are not very energy efficient. A super-capacitor can give you high peak power if you need that, but will not help at all with the total energy. The work the actuator has to do is significant, so the efficiency matters.



  2. Worse, a shape-memory alloy actuator requires constant power to remain at one end of the motion range and spontaneously returns to the other. However, gear must be stable in both end positions without requiring energy, so there would still have to be uplocks and separate actuator for extension or retraction (or maybe extension would be gravity-only, but then you have to ensure it gets reliably locked). Not really simple anymore.



I also don't think they actually scale to the required forces and displacements well. A 2 mm wire bends quite easily, 2 cm rod, not so much. The thicker will of course need more force to bend—which is OK—but it will also break much sooner, because the difference in strain is bigger.






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    1 Answer
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    $begingroup$

    Shape-memory alloys change their shape with temperature, with control usually achieved with electric heating in one direction, and back with convective heat transfer to the environment. There is one specific temperature where the change in shape occurs. There are two huge problems with this:





    1. The operating temperature range for gear actuators is huge. It may easily be below -40°C on a cold arctic night, but on a hot tropical day the sun can easily heat the structure to upward of +60°C. That means the transformation temperature must be pretty high, but that means a lot of energy has to be put to heating it, especially if the ambient temperature happens to be low on the day.



      Note that the actuators are not very energy efficient. A super-capacitor can give you high peak power if you need that, but will not help at all with the total energy. The work the actuator has to do is significant, so the efficiency matters.



    2. Worse, a shape-memory alloy actuator requires constant power to remain at one end of the motion range and spontaneously returns to the other. However, gear must be stable in both end positions without requiring energy, so there would still have to be uplocks and separate actuator for extension or retraction (or maybe extension would be gravity-only, but then you have to ensure it gets reliably locked). Not really simple anymore.



    I also don't think they actually scale to the required forces and displacements well. A 2 mm wire bends quite easily, 2 cm rod, not so much. The thicker will of course need more force to bend—which is OK—but it will also break much sooner, because the difference in strain is bigger.






    share|improve this answer











    $endgroup$


















      2












      $begingroup$

      Shape-memory alloys change their shape with temperature, with control usually achieved with electric heating in one direction, and back with convective heat transfer to the environment. There is one specific temperature where the change in shape occurs. There are two huge problems with this:





      1. The operating temperature range for gear actuators is huge. It may easily be below -40°C on a cold arctic night, but on a hot tropical day the sun can easily heat the structure to upward of +60°C. That means the transformation temperature must be pretty high, but that means a lot of energy has to be put to heating it, especially if the ambient temperature happens to be low on the day.



        Note that the actuators are not very energy efficient. A super-capacitor can give you high peak power if you need that, but will not help at all with the total energy. The work the actuator has to do is significant, so the efficiency matters.



      2. Worse, a shape-memory alloy actuator requires constant power to remain at one end of the motion range and spontaneously returns to the other. However, gear must be stable in both end positions without requiring energy, so there would still have to be uplocks and separate actuator for extension or retraction (or maybe extension would be gravity-only, but then you have to ensure it gets reliably locked). Not really simple anymore.



      I also don't think they actually scale to the required forces and displacements well. A 2 mm wire bends quite easily, 2 cm rod, not so much. The thicker will of course need more force to bend—which is OK—but it will also break much sooner, because the difference in strain is bigger.






      share|improve this answer











      $endgroup$
















        2












        2








        2





        $begingroup$

        Shape-memory alloys change their shape with temperature, with control usually achieved with electric heating in one direction, and back with convective heat transfer to the environment. There is one specific temperature where the change in shape occurs. There are two huge problems with this:





        1. The operating temperature range for gear actuators is huge. It may easily be below -40°C on a cold arctic night, but on a hot tropical day the sun can easily heat the structure to upward of +60°C. That means the transformation temperature must be pretty high, but that means a lot of energy has to be put to heating it, especially if the ambient temperature happens to be low on the day.



          Note that the actuators are not very energy efficient. A super-capacitor can give you high peak power if you need that, but will not help at all with the total energy. The work the actuator has to do is significant, so the efficiency matters.



        2. Worse, a shape-memory alloy actuator requires constant power to remain at one end of the motion range and spontaneously returns to the other. However, gear must be stable in both end positions without requiring energy, so there would still have to be uplocks and separate actuator for extension or retraction (or maybe extension would be gravity-only, but then you have to ensure it gets reliably locked). Not really simple anymore.



        I also don't think they actually scale to the required forces and displacements well. A 2 mm wire bends quite easily, 2 cm rod, not so much. The thicker will of course need more force to bend—which is OK—but it will also break much sooner, because the difference in strain is bigger.






        share|improve this answer











        $endgroup$



        Shape-memory alloys change their shape with temperature, with control usually achieved with electric heating in one direction, and back with convective heat transfer to the environment. There is one specific temperature where the change in shape occurs. There are two huge problems with this:





        1. The operating temperature range for gear actuators is huge. It may easily be below -40°C on a cold arctic night, but on a hot tropical day the sun can easily heat the structure to upward of +60°C. That means the transformation temperature must be pretty high, but that means a lot of energy has to be put to heating it, especially if the ambient temperature happens to be low on the day.



          Note that the actuators are not very energy efficient. A super-capacitor can give you high peak power if you need that, but will not help at all with the total energy. The work the actuator has to do is significant, so the efficiency matters.



        2. Worse, a shape-memory alloy actuator requires constant power to remain at one end of the motion range and spontaneously returns to the other. However, gear must be stable in both end positions without requiring energy, so there would still have to be uplocks and separate actuator for extension or retraction (or maybe extension would be gravity-only, but then you have to ensure it gets reliably locked). Not really simple anymore.



        I also don't think they actually scale to the required forces and displacements well. A 2 mm wire bends quite easily, 2 cm rod, not so much. The thicker will of course need more force to bend—which is OK—but it will also break much sooner, because the difference in strain is bigger.







        share|improve this answer














        share|improve this answer



        share|improve this answer








        edited 3 hours ago

























        answered 3 hours ago









        Jan HudecJan Hudec

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