Abuse Loads 1

[Ruag]

Hi guys,
does anyone know something about "abuse loads"?
Can you suggest me some references or give me some tips how to quantify them?
Thanks!

 

[rb1957]

also called "ground handling" loads. vary by company and installation. seen anything from 50lbs to 200 lbs (LMT); the extreme is a jet engine pylon (tail-mounted engines) stressed for a 200 lbs "apron ape" jumping on the (nearly horizontal) pylon, 2g, and that was a limit load, ie 200*2*1.5 = 600 lbs.

we here use a 200 lbs ultimate load applied to the tip of an antenna as a means of "showing" that our antenna support structure is robust (= stiff) enough that we won't have vibration issues with the large VHF blade.

 

[debodine]

We also use "abuse loads" for cabin interior items to show that we have allowed for passenger induced stress.

 

[Ruag]

Thanks guys!

Debodine, what kind of load and entity do you consider for the interiors?

 

[debodine]

Typically I hear the number 300 pounds as an abuse load. That is a number I have heard often from our substantiation group. Since I am not in substantiation myself, I am not aware if there are other values used for different situations.

The one clear example I can positively recall was an assumed abuse load of 300 pounds in a downward direction for an overhead LCD monitor. The scenario was that a passenger would grab the monitor and hang from it. The airline that was our customer at the time reported that as a true incident that occurred on one of their flights, and we now regularly use that assumption for LCD monitor installations since that time.

 

[der8110]

SAE has some documents for seats and galley compnents that include abuse loads for items such as armrests and tray tables. Best part is they include cyclic loads for durability considerations.

 

[berkshire]

Another abuse load, is banging the side of the fuselage by the cargo door with the pallet on a fork lift. I was constantly remaking trim strips at GD to cover MD11 cargo door sills because of this one.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[couts]

Reading at the exchange and all interesting informatoin. Here we try to define different categories of abuse load on different location of our aircrafts for maintenance task ( Ex into the avionics bays):
1) step on ( so far the best values found was 1,5* weight of large operator ( Caesar data) 1.5*250lbs
2) Lean on Fraction of the 250lbs (probable 50% still to be defined)
3) Bump into (Still to be defined)
4) Grab (ex handle)(Still to be defined but probably max weight + safety factor)

I did not see the SAE reference mentioned in the treads, any hint?

The idea for us is to have some generic guidelines for the 4 categories and not analyse in detail each situation ex: the angle of the applied load.
the risk assessment need then to be factored in. Having a ground operator falling Vs breaking a small peace of equipment is different
Of course we want to avoid overengineering by adding too much weight on the A/C.

 

[LessWeight]

I'd also like to see that SAE reference. Couts, you might consider adding a 5th category for areas not accessable to passengers. Outside the passenger cabin there are still things that get stepped on, but you probably don't want to treat every bracket & standoff as something that needs to survive a rare accident involving a whole person's weight. It's more important to let a cheap, easily replaced part get broken. You don't want to carry all that dead weight around, and you want to make sure the bracket breaks before the underlying structure.
So for things that won't be stepped on or are nota ready grab in an awkward access area, or subject to passenger abuse I've seen 50 lb as typical.

 

[rb1957]

like the engine pylon where the ground crew can access the engine (on rear mounted engines). one company uses a 200 lbs "man" with a load factor of 2 (as though he's jumping/falling) as limit ... 600 lbs all up !

 

[verymadmac]

Is there not a mil spec for these types of design loads.