Michael Horowitz wrote:
How does an A&P know if he can simply straighten out a longeron or if
he's going to have to cut and splice?

-----------------------------------------------

I think you've left a few too many loose ends for a concise answer.
However...

The nature and extent of the damage tends to dictate the method of
repair but the airframe usually defines which repair procedures are
most applicable.

Steel tubing without any traumatic injury such as shrapnel wounds or
bullet holes, the degree of deformation and the surface texture tells
you if the member may be straightened or if it should be replace.
Aluminum, due to the stretch resulting from even a minor deformation,
you generally cut it back to clean, un-deformed metal and make up a
splice.

But I'll tell you pard, getting a kink out of a wooden longeron is a
hell of a chore; trying to straighten that stuff just makes it worse,
your rivets don't hold for **** and don't even think of trying to weld
it. Vast mystery I guess.

Or at least, half-vast :-)

-R.S.Hoover