fitting analysis

[minny]

I have to do a fitting analysis. In particular I'm interested in the joint analysis. The fitting has a clevis, bushings and it is connected to the lug of a second fitting with a pin.
Does anyone know in which JAR/FAR I read about the misalignment?

thanks

 

[rb1957]

it might just be in an AC (43.13 would be my bet if it's anywhere in FAR). i expet however that it's a company rule/guideline ... 5% of axial load applied transversely. else maybe a generalised text (Niu's for example)

 

[GBor]

43.13-2B, as I was made ABUNDANTLY aware from AEG, is only applicable to UNPRESSURIZED aircraft UNDER 12,500 pounds, so make sure you "fit" into this category (please read the bitterness in this...long story), but I agree with RB that it is probably a company guideline or a justifyable engineering judgement.

Determine the max clearance between the pin and the hole, misalign the pin by that much and work the geometry. For inline loads, I've seen a Fitting Factor of 1.15 generally applied.

 

[minny]

I didn't find any reference on the misalignment of the acting load at the joint.

 

[rb1957]

in the AC or in your company doc's ??

if the AC ... not surprising.

if your company doc's , then ask your supervisor what he thinks you should do.

how critical is this ? ... is the joint flight critical ? is the margin (without misalignment) small ? both reasons to investigate misalignment. is the margin large ? is the joint secondary structure ? both reasons not to fuss over it.

 

[JJ22mW]

For interior monument attachments (such as tie rod fittings), Boeing Doc. No. D6-55441 specifies to account for an additional load vector that is 10% of the axial load. This works out to a misalignment of about 5.7 degrees. Although some DER's want 7 degrees of misalignment. Just depends on who's approving it sometimes.

 

[minny]

The fitting is primary structure. It joints aileron to the wing.We are in preliminary size phase.
I can't use Boeing doc. I need a generic reference.
What does DER mean?
The use of the misalignment depend on the type of bearing?

 

[minny]

I searched in the JAR 25, in the AC 43.13-2B.
I didn't find any info about misalignment.

 

[rb1957]

"What does DER mean?" ... i guess you're not in the states.

for generic reference try Michael Niu, else use something like 10%. this is not used to define the bearing, but rather to account for "realities", like your load not being axial. The aileron hinge will almost certainly be installed with spherical bearings, the real world being that the two sides of the hinge don't exactly align and the spherical bearing releases the joint, so there is no internal moment/fixity, but the load can still be applied off axis ... clear as mud ?

 

[JQCF1]

GBor
Your finagle factor of 1.15 is right out of 23.625 and probably Part 25 and 27 as well.

The problem is the definition of "fitting"?? I understand a seat belt fitting that goes between the nylon webbing and the seat. But what if the manufacturer identifies a widget as a "bracket" and the FAA says to apply the 1.15 factor.

I disagree but sometimes it's easier to fold-em than fight!!

JQC DER/DAR