Loads Factors to apply to aircraft components for fuselage hoisting operations

[zerhunt]

Hello Everyone, been a long time reader of eng-tips, and just joined to post my first question.

I wanted to know if anyone has a good reference document they could point me to that has recommendations for load factors to use on aircraft components (not the tooling) for a fuselage hoisting operation. Currently I've looked at Bruhn and Niu and couldn't find anything in those texts. I have read through NASA SP-8077 "Transportation and Handling Loads" and couldn't find much there either for hoisting. Thanks

 

[rb1957]

can you explain "fuselage hoisting operation" ? like on the production line ? if so, then maybe 2 is a reasonable guess; if you want a hard number then derive it from the power of the lifting motors.


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

 

[zerhunt]

rb1957 yes on the production line, slings/straps will be used for hoisting.
Currently, I'm planning on using a safety factor of 2 on ultimate. I was hoping to reference a document.
I'm curious about deriving a hard number of the lifting motors, how do I go about doing that, ( once again this is for aircraft structure and not the tooling). thanks

 

[rb1957]

energy/work done ... how much lift force can be applied (by the power of the hoist motors) ? then the load factor is "simple".

There may be a work safety requirement, particularly if the lift is high enough that someone could get underneath (inspite of placards).

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

 

[Sparweb]

A previous discussion on the subject:

http://www.eng-tips.com/viewthread.cfm?qid=365544

STF

 

[zerhunt]

rb1957, so basically take the lift capacity of the crane over the weight of the hoisted structure, (lift capacity)/(wt. of structure)?? I think it makes sense that the max force that can be applied to the structure is the capacity of the overhead crane.

Sparweb the S.F. of 2 on ultimate that I'm planning to use is based on the 14 CFR 25.519 for jacking and tie-down. thanks

 

[rb1957]

that'll give you a rational basis for a load factor; I'd be surprised if it were as high as 1.5, more likely 1.1, so use of conservative factors is understandable. And this load case is probably only critical for the hoist fittings, which you could conservatively size for the strength of the cable being used. However there can be other requirements (health and safety) that may require a larger safety factor.

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

 

[zerhunt]

rb1957 and SparWeb Thank You!!! for your answers.

 

[rb1957]

the factors in 25.519 are not really safety factors (that'd be 25.303, the ultimate factor). 25.519 are conservative load factors to apply to rationally derived loads.

apologies for repeating it, but there are probably other factors to be applied (health and safety law, or your own factory design guidelines).

hoisting inside the factory is not covered by FAR.

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

 

[Sparweb]

"...hoisting inside the factory is not covered by FAR..."

Good point! Elevated loads in a workplace are covered by worker safety regulation. This varies a lot because it is local jurisdictions (states, provinces, territories, federal governments) that make different rules for themselves.

STF