Definition
An early form of aircraft fuselage construction in which the structural framework is built from a network of wood or metal members (longerons, struts, and wire bracing) arranged in triangular patterns to carry flight and ground loads. The framework is left exposed or covered with fabric, with no stressed outer skin contributing to strength.
Plain English
A fuselage built like a skeleton of crossed bars and wires, where the framework itself carries all the loads and the outer covering (if any) is just fabric for shape and airflow.
Context Anchor
Seen when studying fuselage construction, especially on older or fabric-covered aircraft with a visible internal frame.
Derivation
‘Truss’ comes from the Old French ‘trousse,’ meaning a bundle or framework tied together. The same word describes the triangulated frameworks used in bridges and roof beams. ‘Open’ refers to the fact that the framework is visible — not enclosed by a load-bearing skin.
Why Pilots Care
Aircraft built with open truss structures handle damage, repair, and inspection differently from modern monocoque designs. Pilots flying tube-and-fabric aircraft need to understand that structural strength lives in the frame, not the covering, which affects preflight inspection and repair decisions.
Analogy
Think of a bridge made from connected triangles. The strength comes from the frame, not from a thin covering placed over it.
Intuition Check
Do not read “open” as “uncovered.” In this term, “open” means the load-carrying frame has open spaces between its members, even though the fuselage normally has a covering over it.
Example Sentence 1
The Piper J-3 Cub uses an open truss structure made of welded steel tubing covered with fabric.
Example Sentence 2
Older fabric-covered airplanes often use an open truss structure because it is light and strong.