Hi guys!
A friend of mine needs some information on landing gears, and the principle of operation of it, and especially how a gear absorps the shocks when touching down... Since I'm not (yet) able to give that much explanation to her, I ask it here on the forum...
I looked a bit on the net to some interesting sites, and I found some, but do you know other interesting sites on this subject? Please post a link here then!
Thanks already for the help!
Regards,
Wim
Landing gears - principle of operation
Moderator: Latest news team
Hi Wim,
Let me try to summarize what I know:
First of all some general info.
The landing gear system includes:
- Strut
- Shock absorber
- Extraction/retraction mechanism
- Brakes
- Wheel
- Tyre
The main functions of the landing gear are as follows:
1. Energy absorpton at landing
2. Braking
3. Taxi control
About the shock absorber, its main role is to zero the vertical component of the airplane velocity during landing, with no rebound and limited load transfer to the vehicle structure. Its secondary requirement is to allow a comfortable taxiing. Different types of shock absorbers are available, but when costs and dimensions allow, a hydraulic system is commonly used.
Substantially the system structure is made of a moveable piston that, when loaded, compresses a gas (nitrogen) in a cylinder and causes an oil flow through orifices. The system elasticity is due to the gas transformation while the damping effect is due to the liquid pressure losses (through the orifices).
If you want more info I can give you the formulas which will help you size a shocl absorber system of an aircraft. You'll be able to size the brakes, the shock absorber, the strokes during damping etc....
I hope it helps
Chris
Let me try to summarize what I know:
First of all some general info.
The landing gear system includes:
- Strut
- Shock absorber
- Extraction/retraction mechanism
- Brakes
- Wheel
- Tyre
The main functions of the landing gear are as follows:
1. Energy absorpton at landing
2. Braking
3. Taxi control
About the shock absorber, its main role is to zero the vertical component of the airplane velocity during landing, with no rebound and limited load transfer to the vehicle structure. Its secondary requirement is to allow a comfortable taxiing. Different types of shock absorbers are available, but when costs and dimensions allow, a hydraulic system is commonly used.
Substantially the system structure is made of a moveable piston that, when loaded, compresses a gas (nitrogen) in a cylinder and causes an oil flow through orifices. The system elasticity is due to the gas transformation while the damping effect is due to the liquid pressure losses (through the orifices).
If you want more info I can give you the formulas which will help you size a shocl absorber system of an aircraft. You'll be able to size the brakes, the shock absorber, the strokes during damping etc....
I hope it helps
Chris
Strange to the 'landing' gear is that it is not only used to land.
An other word is the undercarriage.
An undercarriage is a structure that supports an aircraft and allows it to move on ground. The main wheels are usually under wing, some aircraft types have (an) undercarriage bogie(s) on the fuselage centreline, eg in line with the nose wheel for the A340.
So what it needs to do on ground is rolling, steering and braking. Once in the air undercarriages have no function at first glance, but on some types of aircraft they help to stabilize low speed flight.
landing gear types and parts of the landing gear.
State-of-the-art landing gear are focusing on the damping function and the energy storage or springing function.
Goodrich is testing landing gear for the next generation of 800 ton (725,750 kg) transport jets.
An other word is the undercarriage.
An undercarriage is a structure that supports an aircraft and allows it to move on ground. The main wheels are usually under wing, some aircraft types have (an) undercarriage bogie(s) on the fuselage centreline, eg in line with the nose wheel for the A340.
So what it needs to do on ground is rolling, steering and braking. Once in the air undercarriages have no function at first glance, but on some types of aircraft they help to stabilize low speed flight.
landing gear types and parts of the landing gear.
State-of-the-art landing gear are focusing on the damping function and the energy storage or springing function.
Goodrich is testing landing gear for the next generation of 800 ton (725,750 kg) transport jets.
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EBAW_flyer
- Posts: 557
- Joined: 29 Sep 2003, 00:00
Here's a site about the Boeing 737 landinggear:
http://www.b737.org.uk/landinggear.htm
http://www.b737.org.uk/landinggear.htm
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Bracebrace
- Posts: 273
- Joined: 04 Apr 2006, 00:00
The basic principle of a shock absorber used on most commercial aircraft: it uses a compressible fluid (a gas) to absorb the energy of the first impact. It's like a bicycle tire pump you "kick" very hard on the handle with a closed outlet. This is the shock absorber function.
However, if you leave it like that, the pump handle will kick back when you release it because of the high internal pressure of the gas inside it. This would mean a landing aircraft would simply bounce back into the air.
To prevent this from happening there's a second cilinder attached to the handle which has both sides filled with a fluid (oil). Here's a small drawing which should make things clearer (I hope).
http://users.skynet.be/ief.cooreman/airoilstrut.GIF
This oil is incompressible and is free to move upwards when you kick the handle in (large arrow through a one-way valve). However, it is restricted to move back downwards (small arrow through restricted hole). When you release the handle after compression, the compressed gas tries to compress the oil in the upper chambre which can only flow back to the lower room slowly. Hence the handle moves back up very slowly.
Same happens on an aircraft, compression on impact goes fast, decompression after the impact slow. The difference with a real air-oil strut on an aircraft is that both cilinders are "telescopic". They are constructed around eachother, instead of seperate units as shown in the graph.
Hope this helps?
However, if you leave it like that, the pump handle will kick back when you release it because of the high internal pressure of the gas inside it. This would mean a landing aircraft would simply bounce back into the air.
To prevent this from happening there's a second cilinder attached to the handle which has both sides filled with a fluid (oil). Here's a small drawing which should make things clearer (I hope).
http://users.skynet.be/ief.cooreman/airoilstrut.GIF
This oil is incompressible and is free to move upwards when you kick the handle in (large arrow through a one-way valve). However, it is restricted to move back downwards (small arrow through restricted hole). When you release the handle after compression, the compressed gas tries to compress the oil in the upper chambre which can only flow back to the lower room slowly. Hence the handle moves back up very slowly.
Same happens on an aircraft, compression on impact goes fast, decompression after the impact slow. The difference with a real air-oil strut on an aircraft is that both cilinders are "telescopic". They are constructed around eachother, instead of seperate units as shown in the graph.
Hope this helps?
there is a download on my site that illustrates the servicing of a shock absorber of the Avro.
hope that helps
greetz
here
hope that helps
greetz
here
Visit www.batechnics.com ! (Belgian Aviation Technics)