A technician examining a fuselage skin panel identifies numerous small, lightweight longitudinal members running between the heavier longerons, spaced closely to support the skin. What is the primary function of these members?
- AThey are bulkheads that give the fuselage its cross-sectional shape
- BThey are spar caps that resist wing bending loads
- CThey are longerons and serve as the primary heavy load-carrying members of the fuselage
- DThey are stringers that stabilize the skin, prevent buckling, and help distribute loads into the frames and longerons
Show answer & explanationAnswer & explanation
Correct answer: D. They are stringers that stabilize the skin, prevent buckling, and help distribute loads into the frames and longerons
Stringers are numerous, lightweight, closely spaced longitudinal members that run between the heavier longerons in a semi-monocoque fuselage. They stiffen and stabilize the skin against buckling under compressive and shear loads and help transfer loads to the frames and longerons, but they are not designed to carry loads as large as the longerons.
Why the other options are wrong
- A. Bulkheads/formers are ring-shaped members giving cross-sectional shape, not longitudinal skin stiffeners.
- B. Spar caps are wing spar members resisting bending loads, unrelated to fuselage skin stiffening.
- C. Longerons are the heavier primary longitudinal members, not these lighter, numerous stiffeners.
Stringer vs Longeron
Stringers are lightweight, numerous longitudinal skin stiffeners that prevent buckling and distribute loads, whereas longerons are the heavier, primary longitudinal load-carrying members in a semi-monocoque structure.
- Stringers are more numerous and lighter than longerons
- Stringers primarily stabilize skin against buckling
- Longerons are the main heavy longitudinal load path
- Both run the length of the fuselage between frames/bulkheads
Memory trick: Longerons are the 'long strong' bones; stringers are the many small strings holding skin taut.