Need Help on Landing Gear Calculations

"Dick" wrote

Just thinking out loud here but thought the +/- 6 G was for airframe, etc in
flight while the landing gear get subjected to considerably less. Vaguely
remembering the FAA requirements as 3 times static wheel load dropped 19". I'm
thinking 300# on one mains times 3.

True, the G rating for an airplane is for the airframe, but how many G's would a
drop from 19" develop?

I don't have the slightest idea. I'm not a wiz on math problems.

If a drop from 19" does not stress the plane to more than 3 G's, that would be a
wimpy test, in my opinion. A plane dropping in on a blown landing hits with a
real whack. How about it, you out there with G meters? How high of a reading
have you seen on a really blown landing?

It should not be that tough, for a wiz at math to figure out how hard of a whack
a 19" drop generates. Take the speed generated, and divide that result out into
the amount of suspension travel, I would think.

The whole key in the difference is that the G rating for an airframe is
generated and suspended by the wings, and the G rating for the landing gear is
generated by changing velocity into a stop by the landing gear.
--
Jim in NC

"Bryan Martin" wrote

It's a bit more complicated than that. Assuming the suspension acts like
a spring, the force applied will increase linearly as the deflection
increases. So the acceleration will increase as the suspension deflects.
Of course you would design the suspension so that it won't bottom out in
the 19" drop test because things get even more complicated if that
happens.

Yeah, I know. I thought about that, and chose to ignore it. g 'Kinda like
the frictionless physics problems, you know. ;-)

I suppose if you wanted to, you could place limits on the shock absorbing, or
spring rates, and where it would bottom the suspension. Say something like the
force required to bottom the suspension of a 1300 pound plane is twice that of
the weight of the plane, and upon bottoming the suspension, the bottoming stop
only gives another one inch. That (to my simple math mind) sounds like some
really nasty calculus, and I wouldn't even know how to set up the problem, let
alone solve it. :-)
--
Jim in NC