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Landing Gear

Landing Gear

Landing Gear

(OP)
how to calculate the landing gear damping coefficient and stiffness for a non linear Spring type.
I have only the mass of helicopter = 5126 Kg

and initial velocity of 0.5m/s .

Can anybody help please

thanks

RE: Landing Gear

i suspect that we need more information to help ...

RE: Landing Gear

(OP)
the maximum deflection has been provided which = 0.3 m (Value Assumed ) For lynx 300 Helicpter
Mass of the helicopter = 5126 Kg
sink speed = 0.5m
k= F/x = 5126/0.3 = 167620.2 N/m

Need to find out damping ratio and Damping Coeficient at which the helicopter will have a deflection of 0.3 m

RE: Landing Gear

ok, now you've told us the limiting displacement, and calc'd a linear stiffness. wrongly btw (is the helicopter's mass 5126 kg or is it it's weight ?)

but damping controls how the systems responds to step changes over time ... does it bounce ?
which'll require other data

RE: Landing Gear

(OP)
5126 is the mass
and it should bounce because its landing on a aircraft carrier. we have to assume the time

thanks

RE: Landing Gear

"it should bounce because its landing on a aircraft carrier"

Do you mean it should NOT bounce?

RE: Landing Gear

if the mass is 5126 kg, then it's weight will be 5126*9.81 = 50240 N (no?)
but i wonder if that's the right force to apply (btw, there are two skids supporting the helicopter, so each supports 1/2 the weight)

maybe an energy equation, the initial kinetic and potential energy are converted into spring energy

1/2mv^2+mgh = 1/2kx^2 ... (h = x ??)

... but i don't think that's the right spring energy ... it's not like there's a spring mounted under the fuselage, being compressed; it's more like a leaf spring.

RE: Landing Gear

(OP)
ours is oleo pneumatic type this is modeled as mass spring damper system
the landing gear system is a tricycle type.

RE: Landing Gear

ok, so if you have a oleo gear it'll compress on impact and rebound in some way. and then it'd be reasonable to assume x = h (in the previous energy balance).

still the reasonable assumption would be landing on the two main gear.

this is starting to sound suspiciously like a school problem ...

RE: Landing Gear

It's like watching a train wreck in slow motion.

OK, is the load split between all three legs?

Secondly, what is the complete list of your design aims? I gather maximum deflection of 0.3m is one. Or are you saying the spring deflection at rest is 0.3m?

If you don't have any damping then the helicopter will land, compress the spring, and then bounce back into the air.

"k= F/x = 5126/0.3 = 167620.2 N/m"

wrong. Or at least, if it happens to be right it'll be because of coincidence not logic.

Cheers

Greg Locock


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