Structures, loads and margins
Size the structure against real loads, and keep the margins that prove it.
Structures, loads and margins
Structural margins are frequently asserted rather than shown. A number appears in a report, the aircraft flies, and when a certifier or an incident asks where the margin came from, the derivation is a memory rather than a record.
Loads come from the aerodynamics and mass, which keep changing through design. A margin computed against last month's loads is not a margin, and reconciling structure with a moving design by hand is exactly where errors hide.
Spar sizes the structure against the loads derived from the current airframe definition, and every margin carries its inputs and method. When the design moves, the margins recompute, and the evidence travels with them into the airworthiness record Hangar keeps.
Spar closes the design triangle with Planform and Camber: one airframe definition, sized aerodynamically and structurally against the same assumptions.
Tell us what you are flying and where the programme is losing time. We will tell you honestly which of these helps and which does not.