Landing gear attach point composite load

[jfair]

Hi

I'm searching the best way to attach a fixed main landing gear for an homebuilt aircraft of 1200lbs gross (planned.) The landing gear leg will be a spring type or a rubber donut type. But for the fixture onto a composite wing section :

1- A bracket directly fastened on the spar web
2- The leg having a T shape at top that attach to: spar and front plate in D-cell, as extra wing rib.

And in both case, is the spar cap must be adjusted to the extra shock load at landing Or just by extra ply for the web.. ? Or the load reaction is better spread in 2 supporting member as on the picture.. ?

Many thanks

 

[stressebookllc]

Is more oxygen better than less oxygen? Yes in that sense I'd think more support points are better to distribute the load, obvious.

But at what cost are you making that extra oxygen or spreading the load? That is what you really need to focus on in my humble opinion.

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[rb1957]

as i understand your sketches, the choice is between cantilevering the LG directly off the spar (LH fig) or building up a structure around the LG pintle so that the load is distributed into the spar (RH fig).

you have to remember the class of plane being worked on (kit built, 1200 lbs) ... so simple crude structures can work, and expensive, complex structures may cost the plane out of business.

If you do go the simple concentrated load path, build a heavy fitting to take the load. Remember all the "odd" direction loads, so that your single point cantilever can react all the loads from the LG. I suspect your fitting will need a sizeable socket to pick up the pintle well.

remember too sometimes you have stiffness constraints ... something may be statically adequate, but too flexible.



another day in paradise, or is paradise one day closer ?

 

[jfair]

Hi
Thanks for reply rb1957. So by going with an heavy plate just like this one :

That could spread the load accordingly. .?

As I plan for an I beam, I might be in need for an extra bracket. But in both case, if a dual mount point is used, with an hard landing, is the spar will might get delamination... If that's the case, a single point will be ok, as I will have to scrap the whole wing anyway.

 

[rb1957]

looks ok for a concept ...

another day in paradise, or is paradise one day closer ?