Douglas Harper's Etymology Dictionary
1912, from French longeron, from longer "to skirt, extend along," from allonger "to lengthen" (see lunge).
Wiktionary
n. A thin strip of wood or metal, to which the skin of an aircraft is fastened.
Wikipedia
In aircraft and launch vehicle construction, a Longeron, or stringer or stiffener, is a thin strip of material to which the skin of an aircraft or propellant tank may be fastened.
Usage examples of "longeron".
So, we must deal with spars, stringers, bulkheads, ribs, formers, longerons and leading edge strips, all of which have definitions unique to wooden airplanes (as opposed to boats and ships).
A silhouetted figure stepped into the display from starboard, pointing forward to the ragged, blasted edges of the hull where crews in battlesuits focused unwieldy, hoselike N-ray projectors on the blazing hullmetal while others dragged massive shoring clamps to secure shattered ribs and longerons from further damage.
They are held in place by longerons and stringers—wooden strips that run the length of the fuselage.
It was big, taking up the major volume of the round-bottomed chamber-the deck on which he presently stood was no more than a small platform mounted over the stout longerons and curved hullmetal plates that formed the underside of the module itself.