Why complex landing gears are used instead of simple,reliability and light weight muscle wire or shape memory...
$begingroup$
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.)
aircraft-design landing landing-gear
New contributor
$endgroup$
add a comment |
$begingroup$
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.)
aircraft-design landing landing-gear
New contributor
$endgroup$
$begingroup$
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
7 hours ago
add a comment |
$begingroup$
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.)
aircraft-design landing landing-gear
New contributor
$endgroup$
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
aircraft-design landing landing-gear
New contributor
New contributor
edited 6 hours ago
SRD
New contributor
asked 7 hours ago
SRDSRD
343
343
New contributor
New contributor
$begingroup$
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
7 hours ago
add a comment |
$begingroup$
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
7 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
7 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
7 hours ago
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
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:
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.
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.
$endgroup$
add a comment |
Your Answer
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "528"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
SRD is a new contributor. Be nice, and check out our Code of Conduct.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2faviation.stackexchange.com%2fquestions%2f62546%2fwhy-complex-landing-gears-are-used-instead-of-simple-reliability-and-light-weigh%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
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:
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.
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.
$endgroup$
add a comment |
$begingroup$
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:
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.
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.
$endgroup$
add a comment |
$begingroup$
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:
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.
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.
$endgroup$
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:
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.
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.
edited 6 hours ago
answered 6 hours ago
Jan HudecJan Hudec
40.8k4107197
40.8k4107197
add a comment |
add a comment |
SRD is a new contributor. Be nice, and check out our Code of Conduct.
SRD is a new contributor. Be nice, and check out our Code of Conduct.
SRD is a new contributor. Be nice, and check out our Code of Conduct.
SRD is a new contributor. Be nice, and check out our Code of Conduct.
Thanks for contributing an answer to Aviation Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2faviation.stackexchange.com%2fquestions%2f62546%2fwhy-complex-landing-gears-are-used-instead-of-simple-reliability-and-light-weigh%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
$begingroup$
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
7 hours ago